Ap dụng phương pháp phân tích kích hoạt nơtron dụng cụ (INAA) trên lò phản ứng và phương pháp xử lý thống kê đa biến trong nghiên cứu đặc trưng đa nguyên tố và xuất xứ của vật liệu khảo cổ đất nung thu thập từ một số khu di c

DANH MUC CAC CHlT VIET TAT Multivariate Statistical Analysis MVSP Program Multivariate Statistical Package Co quan Nang luang Nguyen tir Quoc te Khoi pho ke plasma cam ung doi ngau

BO KHOA HOC VA CONG NGHE

VIEN NANG LlTOfNG NGUYEN TU* VIET NAM

•<ft

BAO CAO TONG KET

DE TAI KHOA HOC CONG NGHE CAP B O

NAM 2007-2008

Ap dung phirong phap phan tich kich hoat notron dung cu

(INAA) tren lo phan irng va phirong phap xu ly thong ke da

bien trong nghien ciru dac trimg da nguyen to va xuat xir

cua vat lieu khao co dat nung thu thap tir mot so khu di chi,

di tich 6^ Viet Nam

•

(Ma so: DT.06/07-09/NLNT)

Ca quan chu tri: Vien Nghien cihi Hat nhan

Chu nhiem de tai: NCV, Ths Cao Dong Vu

Da Lat-12/2009 ^<^/^1

DANH SACH

NHCTNG NGlTcn THAM GIA THlTC HIEN DE TAI

(Sap theo thu tua, b, c, )

Nguyen Kim Dung

Pham Thi Hai

Nguyen Van Minh

Pham Ngoc Som

Nguyen Thi Sy

Le Thj Ngoc Trinh

Cao Dong Vii (CNDT)

Ghi chii: GV: Gidng vien

CV; Chuyen vien

vien chirc

Thac sy, GV Tian sy, NCVC Ti6n sy, NCVC

Cu nhan, CV Ti8n sy, NCVC Thac sy, NCV Cii nhan, NCV Thac sy, NCVC Thac sy, NCV

NCV: Nghien cuu vien NCVC:Nghien ciru vien chinh

Don vi cong tdc

Dai hoc Da Lat Vien Nghien cuu Hat nhan Vien Khao co hoc Viet Nam Bao tang Lam Dong

Vien Nghien cuu Hat nhan

n t

n t

n t

n t

-CO QUAN PHOI HOP THlTC HIEN

1 BAO TANG LAM DONG, 04 Hung Vuffng, Da Lat, Lam Dong

2 VIEN KHAO CO HOC VIET NAM, 61 Phan Chu Trinh, Ha Noi

MUC LUC

• •

Trang

DANH SACK NHUTSIG NGl/ClI THAM GL\ 1

CO QUAN PHOI HOP THU'C HIEN 1

MUC LUC 2 DANH MUC CAC CHU" VIET T A T 3

ABSTRACT 5

G\6\ THIEU 9

NHUNG N O I DUNG DA DANG KY 12

Phan 1: TONG QUAN 13

I Nghien cuu nguon goc trong khao co 13

II Phuang phap phan tich kich hoat natron - NAA 23

III Xu ly thong ke da bien 32

IV Luu do qui trinh nghien cuu nguon goc vat lieu khao co dat

nung bang phuang phap NAA va thong ke da bien 38 Phan 2: THI/C NGHIEM 39

I Thu thap mau 39

II Xay d\mg qui trinh phan tich kfl-NAA 41

III Thiet kl chuang trinh MSAP 54

I Ket qua phan tich 61

II Ket qua xu ly thong ke 64

GlAl TRINH KINH PHI 79

CAc CONG TRINH KHOA HOC DUOC BIEN SOAN vA CONG 80

BO TRONG KHUON KHO DE TAI

PHU LUC 84

DANH MUC CAC CHlT VIET TAT

Multivariate Statistical Analysis

MVSP

Program Multivariate Statistical Package

Co quan Nang luang Nguyen tir Quoc te

Khoi pho ke plasma cam ung doi ngau

Phan tich kich hoat natron dung cu

Phuang phap chuan hoa k-zero

trong phan tich kich hoat natron Khu Di Tich

Gidi han phat hien (dinh tinh) Giai han phat hien (djnh lugrng)

Lo Phan Ung Chuang trinh xu ly thong ke da bien (Da Lat)

Chuang trinh xu ly thong ke da biSn (UK)

Phan tich kich hoat natron Nghien Cuu Hat Nhan Vien Chuan va Cong nghe Quoc gia (Hoa Ky)

Phan tich thanh phan chinh Thanh phan chinh

Phan tich kich hoat ncrtron bang gamma tiic thai

Phong Thi Nghidm

ChUt Viet at Tieng Anh Tieng Viet

RSD Relative Standard Deviation

SAM Sample

SD Standard Deviation

SOC Start of Counting

SPSS Statistical Package for Social

Sciences

SRM Standard Reference Materials

UBNN (People's Committee)

UNESCO United Nations Educational

Scientific and Cultural Organization

V H T T Culture Information

XRFA X-Ray Fluorescence Analysis

Do lech chuan tuang doi Mau

Do lech chuan Bat dau do Chuang trinh xu ly thong ke dung trong khoa hgc xa hgi (Hoa ky) Chat chuan tham khao

Uy Ban Nhan Dan

To chiic Khoa hgc, Giao due va Van hoa Lien Hiep Quoc

Van hoa Thong tin Phan tich huynh quang tia X

ABSTRACT

Application of chemical composition determination of archaeological sample as a support tool for provenance research has quickly developed in the recently decades, particularly in the Latin American countries Many analyzing methods such as, XRFA, NAA, ICP-MS, AAS, etc., have been used for this purpose The most effective and successful method, however, is NAA which has been carried out by some groups all over the world ''^

In Vietaam, problem of determining the provenance of archeological samples by scientific tools has not been employed Some previous researches were not completely done and can not thoroughly solve the provenance question

Twenty five years since Dalat nuclear research reactor has been renewed and operated, along with other trends of research Instrumental Neutron Activation Analysis

re INAA has being invested and successflilly applied in different disciplines such as: geology, environment, petroleum, agriculture, biology, etc

Besides, there are some highly culture remains and ruins of archaeology which need to be researched, preserved, maintained and restored in Viemam From that fact, along with the success of some smdies on the world in the recently decades, in combine

with the domestic archaeologist, we carried out a theme named "Application of

reactor-based INAA and multivariate statistical analysis technique for multielements characterization and provenance research of archaeological materials collected from some archaeological site, relic places in Vietnam"

Collection of provenance information from the multi-elemental characterization and their interrelations is the goal of the authors The obtained results from this study are the first foundation for setting up a database of raw-clay material in some places in Vietaam; Take part in the provenance research on pottery and the restoration of highly culture remains and ruins which are being naturally devastated In this research, 03 archaeological sites were chosen for investigation, as follow: (1) Cattien archaeological site (Lamdong), (2) My Son Holy land (Quangnam), and (3) Emperor's rampart relic (Binhdinh)

The contents of our research includes: (i) Investigation and collection more than

250 samples (raw-clay materials, ancient brick and pottery) at 03 archaeological sites;

(ii) Setting up the multi-element analyzing procedure by the reactor-based ko-NAA method; and (iii) Designing of 01 computer program in order to statistically treat the data by Principal Components Analysis (PCA) and Clusters Analysis (CA)

The main results of this study can be summarized as follow: (1) The analyzing procedure for 29 elements (Al, As, Ba, Ce, Co, Cr, Cs, Dy, Eu, Fe, Ga, Hf, K, La, Lu,

Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Ti, Th, U, V and Yb) by ko-NAA method was set

up, (2) Analyzed data with 8062 analytes for 29 elements, as mentioned above, in 278 archaeological samples and raw-clay materials collected in this study were achieved, and (3) A computer program for statistical multivariate analysis PCA and CA was designed and developed Initial information about the provenance of collected samples was suggested

TOM TAT

Viec ap dung cac phuang phap phan tich thanh phan hoa hgc Uong vat lieu khao

CO dat nung (dat set nguyen lieu, gach, gom sii, do tao tac dat nung, v.v ) de ho trg cho nghien ciiu nguon goc da phat trien mgt each nhanh chong frong vai thap ky qua, dac biet la a cac nuac My La-tinh Co nhieu ky thuat phan tich nhu XRFA, NAA, ICP-MS, AAS, v.v , da dugc sii dung de xac dinh dac tnmg thanh phan da nguyen to cac vat lieu khao CO, tuy nhien, phuang phap co thai gian su dung dai nhat va dugc danh gia la thanh cong nhat trong lich su iing dung trong nghien ciiu nguon goc chinh la phuang phap NAA (Neufron Activation Analysis)''

Q Viet nam, van de nghien ciiu nguon goc cac vat lieu khao co bang cac cong cu khoa hgc hien dai duong nhu chua timg dugc ap dung truac day, hoac neu co ciing chi dung lai a nhung nghien ciiu rai rac chua giai quyet bai toan nguon goc mgt each triet

dk

Hai muai lam nam qua, tir ngay Lo Phan Ung (LPLf) dugc khoi phuc va dua vao khai thac, sii dung, cimg vai nhiing huang nghien ciiu khac tai Vien Nghien ciiu Hat nhan (NCHN), phuang phap phan tich kich hoat nafron dung cu (Instrumental Neutron Activation Analysis - INAA) ciing da dugc dau tu, nghien ciiu phat trien va ting dung thanh cong frong nhieu ITnh vuc nhu: Dia chat, moi truang, dau khi, nong nghiep, sinh hgc, v.v

Ben canh do, a nuac ta hien dang ton tai kha nhieu cac cong trinh kien tnic co, phe tich khao co hgc can dugc nghien ciiu, bao duong, trimg tu va ton tao Tir nhting thuc te nhu vay, cimg vcri thanh tuu tren the giai da dat dugc trong nhimg thap ky qua, ket hgp

vai cac nha Khao co trong nuac, chiing toi da xay dimg mgt de tai ve "Ap dung phucmg phdp phdn tich kich hogt natron dung cu (INAA) tren Id phdn img vd phucmg phdp xic ly thdng ke da bien trong nghien ciru ddc trung da nguyen td vd xudt xu cua vdt lieu khdo

cd ddt nung thu thdp tie mot sd khu di chi, di tich a Viet Nam "

Thu thap thong tin, dii lieu dac trung ve nguon goc cua cac vat lieu khao co dat nung tir dac tnmg thanh phan da nguyen to va moi tuang quan giiia chiing la muc tieu

ma nhom tac gia de tai nham den Tir do, dat nen mong cho viec tao lap ca so dir lieu ve dac trung thanh phan hoa hgc cho dang nguyen lieu, cho cac vimg nguyen lieu set d Viet Nam nham gop phan vao viec nghien ciiu nguon goc do tao tac dat nung co Ngoai

ra, nhirng ket qua nghien ciiu nay con la cii lieu tham khao quan frgng cho cac nha xay dung frong nghien ciiu tim ngudn nguyen lieu phu hgp phuc vu cong tac trimg tu va ton tao cac khu di tich, phe tich co gia tri van hoa cao dang ngay cang xu6ng cap va mai mgt Trong khuon kh6 cua nghien ciiu nay, ba dia diem dugc chgn de khao sat la: (1) Khu di tich khao c6 hgc Cat Tien (Lam D6ng), (2) Khu di tich My San (Quang Nam), (3) Khu di tich Thanh Hoang De (Binh Dinh)

Nhiing ngi dung chu y8u cua dk tai bao g6m: (i) Khao sat va thu thap fren 250 mau

vat (mau dat set nguyen lieu, gach co va g6m c6) tai 03 khu di tich neu fren; (ii) Xac lap qui trinh xac dinh da nguyen to frong cac vat lieu khao co bang ky thuat ko-NAA fren

LPU; Va (iii) thilt ke 01 chuang trinh may tinh dk xii ly thdng ke bg s6 lieu phan tich

fren ca sa sir dung hai phuang phap xir ly thong ke da bien la phan tich thanh phan PCA (Principle Components Analysis) va phan tich nhom CA (Clusters Analysis)

Nhirng ket qua chinh da dat dugc qua de tai c6 the tom tat nhu sau: (1) Bg qui frinh phan tich 29 nguyen to (Al, As, Ba, Ce, Co, Cr, Cs, Dy, Eu, Fe, Ga, Hf, K, La, Lu,

Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Ti, Th, U, V va Yb) bing ko-NAA da dugc xac lap; (2) Bg dii lieu phan tich vdi 8062 chi tieu phan tich cua 29 nguyen to neu fren frong

278 mau vat khao co, set nguyen lieu thu thap dugc qua de tai; (3) Xac lap 01 qui trinh xir ly so lieu phan tich bang hai phuang phap thong ke da bien so PCA va CA Ddng thai, Cac thong tin, dii lieu ban dau ve nguon goc cho cac doi tugng nghien cuu da dugc dua ra

GlGl THIEU

Ngudn goc, theo dinh nghia frong khao co hgc la mgt khoa hgc ve cac loai co vat

tao tac ma trgng tam la xac dinh nguon goc dia ly cua chiing bang each so sanh dac trung hoa hgc cua cac vat lieu co nguon goc da biet vai cac mau chua ro lai lich Qua trinh nay thuang bao gom viec xac dinh cac tinh chat vat ly, hoa hgc cua cac vat lieu de lam nen co vat Nai ma mgt co vat dugc tim thay co the each xa hang ki-16-met hoac hang tram ki-16-met tir nai no dugc tao thanh va giiia chiing co the la mgt khoang thai gian dai su dung hoac frao ddi

Ngoai yeu to nien dai, cac thong tin ve nguon goc cua di vat co vi tri dac biet quan trgng frong nghien ciiu khao co No giiip cho cac nha nghien ciiu co them thong tin, cir lieu trong viec giai ma, lien ket, kiem chiing va luan giai cac van de ve khao co, nhan chung, lich su, v.v Tir do, hieu biet ky luang han ve cac hoat dgng san xuat cua nguoi

CO, tim ra nhirng con duong giao thuang mua ban cac nguyen lieu tho, san vat tao tac, ciing nhu cac mo hinh di tni trong qua khii '^'

Trong nghien ciiu khao co hgc, do tao tac dat nung (pottery) la doi tugng frgng tam Vdi kha nang ton tai frong thai gian dai ma khong bi phan huy, cac san vat tao tac, manh va la thong diep ro net nhat ma nguoi xua de lai Ngoai ra, no con dugc xem la san pham cua qui trinh cong nghe dau tien cua loai nguai

O nuac ta, frong kho tang di san kien tnic cua dan tgc, nghe thuat kien tnic Champa co vi tri dac biet quan trgng Trong suot mgt thai gian dai, gan 900 nam tir cuoi the ky thii VII den niia dau the ky XVII, nguoi Cham da xay dung nen mgt nen kien tnic dgc dao vdi hang tram den thap, trai dai suot tu dai dat mien Trung, Tay Nguyen den vimg Nam bg Qua bao thang tram ciia lich su, thien tai khac nghiet va thdi gian, ngay nay so lugng den - thap Champa con lai khong nhieu, lai frong tinh trang hu hong, xuong cap nghiem trgng, nhung do la nhimg di san kien tnic v6 gia khong chi cua Quoc gia ma con cua nhan loai, la bang chung ve mgt nen van hoa Champa co rue ra, giau ban sac rat can dugc giu gin, ton tao va bao ton Cho den nay, ky thuat va nghe thuat xay dung den thap ciia nguoi Cham co van con nhieu bi an, dieu nay da thu hiit su quan tam cua nhieu nha khoa hgc trong va ngoai nuac tir nhieu chuyen nganh, nhieu ITnh vuc khac nhau Nhieu de tai nghien cuu theo nhieu hudng khac nhau da dat dugc nhiing

thanh cong nhat dinh Trong do dang chii y co de tai \k ""Nghien cim ky thudt xdy dung thdp Chdm phuc vu trung tu vdphdt huy gid trj di tich " do TS Trdn Ba Vi?t thugc Vi^n

Khoa hgc Cong nghe Xay dung thugc Bg Xay dung lam chii nhifm De tai da khong nhimg di sau giai quyet cac van de khoa hgc, cong nghe trong xay dung den thap Champa, ma con lam ro han rat nhieu van de hen quan ve lich sii, nghe thuat, khao c6, dan tgc, kiln tnic, v.v '^^ Tuy vay, mang nghien ciiu ve dac trung thanh phSn hoa hgc cua cac vat lieu khao c6 dit nung nham phuc vu cho nghien ciiu nguon goc frong khao c6 de tai fren da khong de cap din Ngoai ra, mgt so cong trinh nghien ciiu dan le khac

da timg dua ra vSn dl, song, bai toan vl nghien ciiu nguon goc vin con bo ngo va chua dugc tap trung giai quylt mgt each triet de, frong khi do nhung thong tin ve nguon goc

CO mgt y nghia rat lan frong nghien ciiu khao co hgc

Trong nghien ciiu nguon goc cac mau vat tao tac khao co dat nung nhat thiet phai

di tir dac trung thanh phan hoa hgc ciia chiing va cac nguon nguyen lieu kha di de lan theo dau tich cua timg manh va rieng biet tir nai phat hien ra chiing cho den nai chiing dugc tao rạ Nhieu ky thuat phan tich nhu XRFA, NAA, ICP-MS, AAS, v.v da dugc sir dung de xac dinh thanh phan da nguyen to cac vat heu khao co, tuy nhien, phuang phap CO thai gian sir dung dai nhat va dugc danh gia la thanh cong nhit frong lich su ling dung trong nghien ciiu nguon goc chinh la phuang phap NAẤ^

Q Viet Nam, cac phuang phap co dien thuang dugc su dung tir truac cho din nay

trong xac dinh nguon goc co vat noi chung, co vat dk nimg noi rieng la cac phuang

phap so sanh true quan dua vao viec nghien ciiu cac tai lieu tir xua dl lai, dua fren cac hga tiet, hoa van ciia co vat, ciing nhu tir cac thong tin ve nien dai, van hoa v.v Cac phuang phap nay to ra it hieu qua trong nhung truong hgp nhu: C6 vat bi biin dang do dieu kien tu nhien, do thai gian, v.v cung nhu cac san pham dugc tao ra tir su giao thoa ciia cac nen van hoa khac nhaụ

Hai muai lam nam qua, tir ngay Lo Phan Úng (LPU) Hat nhan (Da Lat) dugc khoi phuc va dua vao khai thac, su dung, cimg voi nhirng hudng nghien ciiu khac tai Vien Nghien ciiu Hat nhan (NCHN), phuang phap phan tich kich hoat nafron dung cu

(Instrumental Neufron Activation Analysis - INAA) ciing da dugc dkn tu, nghien ciiu phat trien va iing dung thanh cong frong nhilu linh vuc nhu: Dia chk, moi truang, dau

khi, nong nghiep, sinh hgc, v.v

Tir nhiing ket qua dat dugc fren till gidi ve nghien ciiu ngudn gdc, nhung tiln bo

frong ITnh vuc phan tich hat nhan frong nudc va nhu cki thuc tl cua nganh khao c6 hoc nudc nha vl nghien ciiu ngudn gdc cac di vat dk nung, phdi hgp voi cac nha khao c6 frong nuac, de tai "Ap dung phuang phdp phdn tich kich hogt natron dung cu (INAA)

tren Id phdn ung vd phuang phdp xu ly thdng ke da bien trong nghien cuu ddc trung da nguyen td vd xudt xic cua vdt lieu khdo cd ddt nung thu thdp tir mgt sd khu di chi, di tich

a Viet Nam " da dugc xay dung va thuc hien trong 2 nam (2007-2008), vdi kinh phi

350,0 trieu dong

De tai nay dat ra nham muc dich md ra hudng iing dung mdi cho nganh phan tich hat nhan d Viet Nam va gop phan vao giai quyet bai toan nghien ciiu ngudn goc trong khao CO ma doi tugng chinh la co vat dat nung, bao gom: Set nguyen lieu, gach co va do tao tac noi chung Trong do, nghien cuu set nguyen lieu nham muc dich tao ra cac co sd dii lieu ve nguon; Gach co la mgt dang cua di vat dat nung dugc xem la co nguon goc tai cho, lgi dung yeu to nay de nghien ciiu xay dung qui trinh ban dau; Gom sii la doi tugng chinh trong bai toan nghien ciiu nguon goc trong khao co Tuy nhien, de giai quyet van de mgt each day dii tren qui mo toan quoc hay rgng han la khong gian van hoa cua khu vuc (gom nhieu quoc gia lan can) thi can co rat nhieu thdi gian, co khi len den hang chuc nam hay lau hon niia va phai co nguon kinh phi, nhan luc dii ldn, vdi su tham gia ciia nhieu chuyen nganh khac nhau nhu khao co, dia chat, dia hoa, vat ly, toan hgc, v.v '^'

Thu thap thong tin, dir lieu dac trung ve nguon goc cua cac vat lieu khao co dat nung tir dac trung thanh phan da nguyen to va moi tuong quan giiia chung la muc tieu

ma nhom tac gia de tai nham den Tir do, thiet lap qui trinh nghien ciiu nguon goc, dat nen mong cho viec tao lap co sd dii lieu ve dac trung thanh phan hoa hgc cua cac dang nguyen lieu, cho cac vimg nguyen lieu, cac dang gom sii, do tao tac dat nung d Viet Nam

De giai quyet muc tieu ciia de tai, ba dia diem dai dien dac trung cho tinh trang cac khu di tich d Viet Nam dugc chgn de khao sat do la: (1) Khu di chi khao co hgc Cat Tien (Lam Dong), (2) Khu di tich My Scm (Quang Nam), (3) Khu di tich Thanh Hoang

De (Binh Dinh) Nhiing ngi dung chii yeu da thuc hien bao gom: (i) Khao sat va thu thap han 250 mau vat (set nguyen lieu, gach co va gom co) tai 03 khu di tich neu tren; (ii) Xac lap qui trinh xac dinh da nguyen to frong cac vat lieu khao co bang ky thuat ko-NAA tren LPU; Va (iii) thiet ke 01 chuang trinh may tinh de xir ly thong ke bg so lieu phan tich tren ca sd su dung hai phuang phap xir ly thong ke da bien la phan tich thanh phan chinh PCA va phan tich nhom nhom CA

NHCTNG NOI DUNG D A DANG KY

1 Khao sat, thilt kl idy mau dam bao cac tieu chi phuc vu nghien cuu khao

c6, tinh dai dien cho vimg, vj tri lay mhi va cac tieu chuan phuc vu cho

phan tich INAA "'

2 Tiln hanh thu thap khoang 210 miu bao g6m: Set nguyen lieu, gach c6,

gom CO tir 3 khu di chi, di tich

3 xay dung quy trinh phan tich da nguyen to trong doi tugmg mau khao co dat

mmg bang INAA cho khoang 32 nguyen to (Na, K, Rb, Cs, Al, Sc, Ti, V,

Cr, Mn, Fe, Co, Zn, As, Sb, Zr, Ce, Nd, Sm, Eu, Tb, Dy, Yb, Lu, La, Hf, Ta,

Ca, Sr, Ba, U va Th) va ap dung phan tich 210 mau thu thap qua de tai

4 Xii ly thong ke da bien de danh gia tuong quan tir bg so lieu phan tich nham

khao sat dac tnmg thanh phan, xuat xii ctia cac mau vat khao co theo timg

loai, nhom mau va vimg lay mau Tir do chi ra cac dac tnmg chi thi cho

timg viing khao sat

Phan 1 TONG QUAN

Trong phan nay chiing toi se trinh bay mgt each tom luge cac van de lien quan den nghien ciiu nguon goc frong khao co hgc va cac phuang phap dugc ap dung

I Nghien cihi nguon goc trong Ichao co

Nghien ciiu nguon goc khao co hgc da va dang phat trien ciing vdi cac nganh khoa hgc dia hoa, dia chat va phan tich Nhiing vat lieu khao co thudng cd nguon goc tir dat,

da, gom, kim loai va v6 so Do cac chat lieu dia chat co su phan bo dia ly khac nhau, chiing ta co the xac dinh dugc nguon goc dua vao su khac biet nay Tir nhung dii lieu phan tich dieu tra, cac nha nghien ciiu co the tra ldi chinh xac cac tao vat do da dugc lam ra tir dau va tir loai nguyen vat lieu nao De tai nay chiing toi tap trung nghien ciiu xay dung qui trinh nghien ciiu nguon goc cho doi tugng vat lieu khao co bang dat nung

1 Ddt set va do tgo tdc ddt nung

Dat set (hay set): La mgt thuat ngu dugc dimg de mieu ta mgt nhom cac khoang vat phyllosilicat nhom ngam nudc, thong thudng co dudng kinh hat nho hon 2\im Dat

set bao gom cac loai khoang chat phyllosilicat giau cac oxit va hidroxit cua silic va nhom cung nhu bao gom mgt lugng ldn nudc tham gia vao viec tao cau tnic va thay doi theo tung loai dat set Dat set noi chung dugc tao ra do su phong hoa hoa hgc ciia cac loai da chiia silicat dudi tac dgng ciia axit cacbonic nhung mgt so loai dat set lai dugc hinh thanh do cac hoat dgng thuy nhiet Dat set dugc phan biet vdi cac loai hat dat da nho khac co frong dat, chang han nhu bim nhd kich thuac nho ciia chiing, hinh dang tao bong hay tao lap, kha nang hiit nudc ciing nhu chi so do deo cao''''^l

Trong cac nguon tai lieu khac nhau, ngudi ta chia dat set ra thanh ba hay bon nhom chinh nhu sau: kaolinit, montmorillonit-smectit, illit va chlorit (nhdm cuoi ciing khong phai liic nao cdng dugc coi la mgt phan ciia dat set va doi khi dugc phan loai nhu

la mgt nhom rieng, trong pham vi phyllosilicat) Co khoang 30 loai dat set 'nguyen chat' khac nhau frong cac nhom nay, nhung phan ldn dat set 'tu nhien' la cac hon hgp ciia cac loai khac nhau nay, cimg vdi cac khoang chat da phong hda khac^'*'^'^'

Sir dung ddt set: Dat set la chat mem deo khi am, dieu nay cd nghTa la rat de tao

dang cho nd bang tay Khi kho nd frd nen ran chac hon va khi bi "nung" hay lam ciing bang nhi?t do cao, dat set trd thanh ran vTnh cim Thugc tinh nay lam cho dat set trd

thanh mgt chat ly tudng de lam cac do gom sii cd do ben cao, dugc sii dung ca frong

nhirng muc dich thuc te cdng nhu dimg de lam do frang tri Vdi cac dang dk set khac

nhau va cac dilu kien nung khac nhau, ngudi ta thu dugc dat nung, gom va sii Loai ngudi da phat hien ra cac thugc tinh huu ich cua dat set tir thdi tien su va mgt trong nhiing dd tao tac sdm nhat ma ngudi ta da bilt den la cac binh d\mg nudc lam frr dit set

dugc lam kho dudi anh n4ng mat trdi Phu thugc vao cac hgp chat cd frong dk, dk set

cd thl cd nhilu mau khac nhau, tir mau frSng, xam tdi mau dd-da cam sam'^l

Da hinh thimh tit dung nham nui hia — da nui tin

(Igneous rocks) Tram tich (sedimentary)

Su phong hoa (-weathering)

Dat set neuj'en

smh-Qiia trinh xoi mon

.1

Set thu cap

(L6ng dong tu nhien)

Qui trinb to nhien

Nghien tan thanh bpt min

• Su dvng * ^ ' ' ™ ^ ^'*° ' • ° ' ^*''" ngwoi) Thai hoi (roi \-ii) ra tv» nhien chiu tac ding aia then uet, thoi gian (Diagenesis)

Khai quat thu thap phan tich dac Dung hoa

Dat set dugc

nung ket frong liia da

tao ra nhiing do gom

sii dau tien va hien

nay nd van la mgt

frong nhiing vat lieu

re tien nhat de san

xuat va sir dung rgng

rai nhat Gach, ngdi,

noi tir dat, cac dd tao

tac nghe thuat tir dat,

bat dTa, than bugi va

tham chi ca cac nhac

cu nhu dan ocarina

deu dugc lam tir dat

set Dat set ciing dugc sii dimg trong nhieu nganh cong nghiep, chSng han frong san xuat giay, xi mang, gom sii va cac bg lgc hda hgc^^'^l

Do tgo tdc ddt nung (pottery): La cac vat dung, cac tac phim nghe thuat dugc

lam bang dat nung bdi cac thg gom Do dat nung bao gom cd 3 loai chinh nhu: D6 gdm thd (earthenware), do sanh (stoneware) va do sii (porcelain) D6 tao tac dit nung duac xem la san pham ciia qui trinh cong nghe dau tien cua loai ngudi co tinh nghe thuat cao

va cdn tdn tai cho den ngay nay Chiing dugc tao ra vdi hai muc dich chinh la phuc vu cho nhu cau sir dung hang ngay va frang fri Nguyen lieu chinh dl san suit la dit set chiia khoang -70% dat set frong thanh phan, phan con lai la phu gia tiiy theo loai cone nghe Chiing thudng dugc tao hinh bang tay, sau do dugc nung d nhiet do cao tir 900-1400°C tiiy theo loai Gdm tho, la loai gom tiiudng khong dugc frang men va dugc nung

Hinh 1: Vong ddi ciia mgt san vat dit nimg^^^

d nhiet do tir 1000-1150°C, sau khi nung thuang cd mau tir trang cho den đ tiiy vao nguyen lieụ

Do sanh thudng dugc nung d nhiet do tir 1200-1315°C,

sau khi nung thudng cd mau xam hoac hoi nau, thudng loai

nay cd trang men

Loai thii 3 la gom sir, thudng dugc lam tir set cao lanh

(Kaolin), co nhiet do nung tir 1200-1400°C, thudng cd mau

trang, cd do ben caọ Co vat dat nung sdm nhat dugc biet cho

den ngay nay la dugc tim thay d Cong hda Sec, dugc san xuat

trong khoang thdi gian tu nam 29.000-25.000 trudc cong

nguyen (hinh 2)'^'

2 Sa luac ve lich sir

Y niem ve phan img hat nhan cd the dugc dimg cho phan

tich dinh lugng dugc Georg Hevesy va Hidle Levy dua ra nam

1936, khi ho chilu mudi cac nguyen to dit hilm bing mgt ^ ' " ^ ^- '^^^^ v? "*

dat nung (Venus of nguon phat natron tu nhien RăBe) (Ehmann va Vance 1991) Dolni) co nien dai

Ho da phat hien thiy nhilu nguyen td dit hilm da trd nen cd khp^ng 30.000 nam

tuoi dugc tim thay d hoat do phdng xa cao sau khi dugc chieu bdi natron, hoat do Cong hda Sec'*' nay dugc phat ra tir nhieu nguyen to khac nhau va giam dan

theo cac tham so thdi gian khac nhau (T1/2) Tu phat hien nay hg da nhan ra ve tiem nang cua viec nhan dien su cd mat cua nhiing nguyen to frong mau vat la hon hgp cua nhieu nguyen to thong qua viec do cac biic xa khac nhau va chu ky ban huy ciia nhirng nguyen to phdng xấ

Trong nhung thap nien 50-60, hang loat LPU tren the gidi dugc xay dung vdi thdng lugng nafron du ldn de cho phep do nhay ciia NAA dat tdi mirc cd the dap iing dugc yeu cau ciia cac bai toan phan tich thuc tẹ Them vao do la nhirng tien bg vugt bac

ve tinh phiic tap, do nhay ciia cac thiet bi ghi do hat nhan va hang fram cac thi nghiem

do dac cac thong sd hat nhan lien quan den phan iing hat nhan nhu tiet dien phan iing, chu ky ban hiiy, do phd bien đng vi, ti so re nhanh , v.v ) da dugc tien hanh''l

Tiem nang iing dung ciia phuang phap NAA lin dau tien da dugc Robert Oppenheimer thira nhan nhu mgt cong cu cua khao co hgc vao miia thu nam 1954, ong

ta da dl nghi Dodson va Sayre tai PTN qudc gia Hoa Ky Brookhaven (BNL) sir dung

phuang phap NAA nhu mgt each kha dT de xac dinh nguon goc cua cac manh gdm khao c6 Ciing trong thdi gian nay, mgt nhom nghien ciiu tai Dai hgc Oxford ciing bit dau tiln hanh nhung th\rc nghiem vdi NAA tren cac doi tugng gom va tiln cd^'l

Nhiing iing dimg ban dau da gap phai tra ngai bdi do phan giai kem cua cac he do phd gamma, nhung sir ra đi cua dau do (detector) Ge[Li] vao dau nhirng nam 1960 da mang lai nhirng cai tiln dang kl ve do phan giai cho cac he do pho, dieu nay da tao ra mgt lan sdng cho ling dung NAA trong nganh khao co hgc Bai bao cao cua Sayre (1965) vl phan tich thiiy tinh c6 la bao cao diu tien ve vỉc su dung va nhung lgi the cua dau do Ge[Li] frong NAẤl

Nam 1969 Perlman va Asaro da dua ra mgt mo ta vl phuang phap chuin hda so sanh trong NAA de ap dung trong xac dinh nguon goc tai PTN Lawrence Berkeley Laboratory (LBL) Tir do NAA dugc cac nha khao co sir dung nhieu ban frong khoang thdi gian 1970-1980 de xac dinh nguon gdc cho cac doi tugng gom co, khoang niii lira (obsidian), da tram tich (chert) va cac dang nguyen lieu khac Den nay, mgt ca sd dii lieu ve thanh phan hda hgc vdi sd lugng mau Ien den hang fram nghin mau da dugc tao lap va lien tuc cap nhat tren toan chau My^''^

Tir nhiing nam 1990 cho den nay, NAA dugc xem nhu mgt cong cu frong nghien ciiu nguon goc cua khao co hgc, cho du so lugng cac LPU tren the gidi cd suy giam, nhung hieu suat va cong suat iing dung NAA trong khao co thi van dugc duy tri d miic cao va ngay cang rgng rai ^

3 Nguyen ly nguon goc

Y tudng ve viec xac dinh nguon goc dua fren thanh phan hda hgc cua mau vat da dugc biet den tir nhiing nam dau cua thap ky 70 Tuy nhien, Weigand va cac cong su cua ong (1977) dugc xem la nhting nguoi dau tien da cd nd luc tim hiiu nguon gdc cac

CO vat thong qua viec phan tich cac thanh phan cua nd mgt each tudng minh qua nguyen

ly CO ban dugc ong phat bieu nhu sau: "Tdn tgi nhiing su khdc biet trong thdnh phan giira cdc ngudn nguyen lieu tu nhien khdc nhau md nd vugt qud su khdc biet giua cdc thdnh phdn quan sdt dugc trong ciing mot nguon nguyen lieu " Ngay nay, phat bilu nav dugc xem nhu la 'Nguyen ly ngudn gdc' ciia cac nha Khao c6^^'

Nd dugc hieu rang do tao tac dugc tao ra tir mgt nguon nguyen lieu tho nao do co the dugc xac dinh mgt each thanh cong thong qua viec phan tich thanh phin hda hoc

ciia chimg, mien la su khac biet giiia cac nguon khac nhau phai du ldn so vdi su khac bi^t giCra chimg trong cimg mgt nguon

Phucmg phdp tiep can: Viec xac dinh nguon goc cd the theo mgt trong hai hudng

rieng biet dugc giai thich bdi H Neff (2000) va dugc dan ra d hinh 3 Neu cac ngudn dugc dinh vi va nhan dien mgt cac ro rang, vi du nhu trong trudng hgp ciia cac ddng khoang niii lira, nguyen lieu tho tir cac nguon nay dugc phan lap, va tu dd, nguon goc ciia cac co vat chua biet dugc so sanh vdi cac nhom da biet ngudn gdc (each tiep can thirl)t'«l

Mat khac, neu nguon dugc phan bo rgng, dac biet diing trong trudng hgp cac nguyen lieu tho lam gom, viec lay mau va phan lap cac ngudn kha dl la rat khd (hay khdng thuc te)

Doi vol nhfing nguon dirac khoanh vung

va de nhan dien (nhirng luong khoang

(obsidian flows) va cac via da lo thien)

(D

Lay mau va phan tich nguyen lieu tho tir cac

nguon da xac dinh

\

Tir nhirng nhom tham khao va nhirng mau da

biet nguon goc, dac tnmg hoa chung mot

each thong ke

i

Lay mau va phan tich cac mau vat chua ro

nguon goc va so sanh chung vdi cac nhom

tham khao da biet

Doi vdi nhirng nguon nguyen lieu tren dien rong va co dvcrag bien khong ro rang (gom, sir)

Hinh 3; Hai each tiep can de xac dinh nguon goc (H Neff, 2000)''' '

Va nhu vay, cac nghien ciiu nguon goc mau gom sir dung each tiep can loai trir theo do cac nhdm tham khao dugc thiet lap tir cac mau gom chua ro nguon gdc (each tiep can thii II) Trong nghien ciiu nay chiing tdi sir dung ca hai each tiep can neu tren

4 Chon lua cdc dia diem nghien cuu

Dua fren cac tieu chi: (1) Tinh can thiet; (2) Tinh dai dien; (3) Kha nang thu thap mau, trong de tai nay ba khu di tich da dugc chgn de khao sat la: Khu di tich Cat Tien: Dai dien cho cac khu di chi khao co hgc dang trong qua trinh nghien ciiu chua ro chu nhan; Khu di tich My Son: Dai dien cho kien tnic Champa da dugc cong nhan bdi UNESCO; Khu di tich Thanh Hoang De: Dai dien cho nen van hda ngudi Viet mugn

Cat Tien Archaeological Site

Hlnh 4: Vi tri tuang ddi cua ba khu di tich dugc chgn khao sat

4.1 Khu di tich Cat Tien (Lam Dong)

Theo quoc 16 so 20 tir Da Lat di TP Ho Chi Minh chimg 150 km tdi nga ba Madaguoi, re phai di gan 40 km niia theo dudng tinh lg 721 se den khu di tich Cat Tien

Di tich Cat Tien hay

con dugc ggi la Thdnh dia

Cdt Tien la mgt quan the di

tich rgng ldn dugc phat hien

nam 1985, gom nhieu phe

tich kien tnic nam rai rac

dgc theo ta ngan (bd frai)

song Ddng Nai, vdi chieu

dai phan bo ban 15km tir xa

Quang Ngai (xa dia dau cua Hinh 5: Gdc Tay Nam mgt phi tich tai go 2C khu Thanh

huyen Cat Tien giap vdi dia Cat Tien dang frong qua frinh khai quat huyen Da Teh) din xa E)iic Pho huyen Cat Tien Cac di tich kiln tnic dugc tap trung chii ylu frong mgt bon dia hep mat Dong, Tay, Bic giap niii bao quanh, mat Nam giap

song Dong Nai tai thon 1 xa Quang Ngai (d day hien cd 11 phe tich kien tnic da dugc khai quat khao co va nhieu thanh to kien tnic khac mdi dugc tham sat nghien ciiu)'"'

12,13,14]

Trai qua 8 lan khai quat khao co (tir nam 1994 den nam 2006) cac nha khoa hgc da lam xuat 16 nhieu cong trinh kien tnic dd la cac dang den thap, mg thap, dai thd, nha dai, mang dan nudc, dudng di lat bang gach da va khu vuc 16 san xuat gach co, v.v Cac kien tnic d day dugc xay dung chii yeu bang gach san xuat tai chd va da khoi van chuyen tir nai khac tdi su dung lam cac cau kien kien tnic nhu cgt da, mi cira va che tac cac ngau tugng Linga-Yony, tugng cac vi than Uma, Ganesa, v.v trong tin nguong An

Do giao Tat ca cac kien tnic dugc khai quat deu d dang phe tich chi cdn phan nen mdng Qua binh do kien tnic den thap, mg thap, v.v cac nha khoa hgc nhan dinh day

la mgt khu thanh dia vdi nhieu den thd chiu anh hudng van hda An Do giao cua mgt cgng dong cu dan co ton tai each ngay nay hom mgt ngan nam'"^

Su phan bo rgng ldn, cac loai hinh kien tnic da dang va cac di vat thu dugc qua cac cuoc khai quat cho thay tam quan frgng, tinh da dang, phong phii ciia khu thanh dia

nay Tren ca sd do cac nha khoa hgc budc dau nhan djnh "'Qudn the di tich Cdt Tien cd quy md rdt lan, mang ddc diem cua mot qudc gia cd cd su phdt trien khd sam, cd mdi quan he rdng vai nhieu nen vdn hda khdc a vung Nam Ddng Ducmg vd the gioi ben ngoai Nien dgi cua di tich dugc dodn dinh tic khodng the ky IV-IX sau cdng nguyen "

Ve van de chii nhan den nay van la mgt bi an chua dugc giai ma, rat can su quan tam nghien ciiu ciia cac nha khoa hgc''^'^^

Vdi quy mo va tinh chat dac biet, thanh dia Cat Tien da dugc Bg VHTT cong nhan

la di tich lich sir - van hda cap quoc gia nam 1997 Nam 2006 co quan chuyen trach la Ban quan ly di tich Cat Tien true thugc sd VHTT Lam Dong dugc thanh lap Nam 2007

Du an quy hoach, tu bo va ton tao khu di tich Cat Tien da dugc Bg VHTT va UBND tinh Lam Dong phe duyet

Thanh dia Cat Tien se dugc dau tu, nghien ciiu, tu bo va ton tao trd thanh mgt khu

du lich Lich sii - Van hda tien tdi lap ho sa trinh chinh phii de nghi UNESCO xet cong nhan la di san van hda the gidi

4.2 Khu di tich My San (Quang Nam)

Khu di tich My Som hay cdn ggi la Thdnh dia My San thugc xa Duy Phii, huyen

Duy Xuyen, tinh Quang Nam, each thanh pho Da Nang khoang 69km va each thanh co

Tra Kieu khoang 20km, la to hgp bao gom nhieu den dai Champa, trong mgt thung liing dudng kinh khoang 2km, bao quanh bdi doi niii Day timg la nai td chiic ciing tl cua vuang trieu Champa ciing nhu la lang mg ciia eae vi vua Champa hay hoang than, quoc thich Thanh dia My San dugc coi la mgt frong nhiing trung tam den dai chinh cua An

Do giao d khu vuc Dong Nam A va la di san duy nhit ciia the loai nay tai Viet Nam''^l

Thong thudng

ngudi ta hay so sanh

thanh dia nay vdi cac

to hgp den dai chinh

khac d Dong Nam A

nhu Borobudur (Java,

Indonesia), Pagan

(Myanma), Angkor

Wat (Campuchia) va

Ayutthaya (Thai Lan)

Tir nam 1999, thanh

^ • ^ Hinh 6; Mgt phan quang canh nhdm thap B, C va D tai Thanh

UNESCO chgn la mgt dia My San

trong cac di san the gidi tai phien hgp thii 23 cua Uy ban di san thl gidi theo tieu chuin

C (II) nhu la mgt vi du dien hinh ve trao ddi van hoa va theo tieu chuin C (III) nhu la bang chiing duy nhat ciia nen van minh Chau A da bien mat''^''^^

My Som c6 le dugc bit diu xay dung vao thl ky 4 Trong nhieu thl ky, thanh dia nay dugc bo sung them cac nggn thap ldn nhd va da trd thanh khu di tich chinh cua van hda Champa tai Viet Nam Ngoai chiic nang hanh le, giiip cac vuang trieu tilp can vdi cac thanh than My San con la trung tam van hda va tin nguong cua cac trilu dai Champa va la nai chon cat cac vi vua, thay tu nhieu quyln lue Nhung di vat diu tien dugc tim thay ghi dau thdi dai vua Bhadravarman I (Pham H6 Dat) (tri vi tir nam 381 den 413), vi vua da xay dung mgt thanh dudng de thd ciing Linga va Shiva My San chiu anh hudng rat ldn ciia An Do ea ve kien tnic - the hien d cac din thap dang chim dam trong huy hoang qua khii, va ve van hda - the hien d cae ddng bia ky bing ehir Phan cd fren cac tim bia

Dua tren cac tam bia van tu khac, ngudi ta bilt nai day da timg cd mot din thd diu tien dugc lam bing go vao thl ky 4 Han 2 thl ky sau dd, ngoi din bi tiiieu buy

trong mgt tran hda hoan ldn Vao dau the ky 7, vua Sambhuvarman (Pham Phan Chi) (tri vi tir nam 577 den nam 629) da dimg gach de xay dung lai ngdi den con tdn lai den ngay nay (cd le sau khi dai do tir Khu Lat ve Tra Kieu) Cac trieu vua sau do tiep tuc m sira lai cac den thap cii va xay dung cac den thap mdi de thd cac vi than Gach la vat lieu tot de luu giir ky lic ciia mgt dan tgc ky bi va ky thuat xay dung thap ciia ngudi Cham cho tdi nay van con la mgt dieu bi an Ngudi ta van chua tim ra ldi giai dap thich hgp ve chat lieu gan ket, phuang thiic nung gach va xay dung''^l

Nhiing nggn thap va lang mg cd nien dai tir the ky 7 den the ky 14, nhung cac ket qua khai quat cho thay cac vua Cham da dugc chon cat a day tir the ky 4 Tong sd cong trinh kien tnic la tren 70 chiee Thanh dia My Son cd the la tnmg tam ton giao va van hda ciia nha nudc Champa khi thii do ciia quoc gia nay la Tra Kieu hay Dong Duomg

Sau khi vuang qudc Chiem Thanh lui tan, thanh dia My Son da chim trong lang quen hang the ky, den nam 1885, nd mdi dugc phat hien Mudi nam sau, cac nha nghien ciiu bat dau thuc hien cac cuoc phat quang, nghien ciiu khu di tich nay

Cd the chia viec nghien ciru cua cac nha khoa hgc Phap ve My Son thanh hai giai doan:

• Tir nam 1898 den 1899: Louis de Finot va Laimet de Lajonquere nghien ciiu cac van bia

• Tir nam 1901 din 1902: Henri Parmentier nghien ciiu ve nghe thuat, nam 1904 ong cimg Olrpeaus to chiic khai quat khao co hgc tai day

Din nam 1904, nhiing tai lieu ca ban nhat ve My Som da dugc L Finot va H Parmentier cong bd Tu cong trinh nghien ciiu ciia H Parmentier, ngudi ta biet each day han 100 nam My San cdn 68 cong trinh kien tnic, va ong da chia chiing thanh cac nhom tir A, A' din N

Nha nghien ciiu nghe thuat P Stem chia di tich Cham Viet Nam thanh 7 phong each nghe thuat theo qua trinh tiln trien cua nd My Son cd dii dai bieu cac phong each, trong dd cd 2 phong each xuit phat tu My Son Dac biet phong each My Son Al vdi xuit phat la din Al thudng dugc ggi la kiet tac kien tnic cua di tich Cham Cac nha khao c6 hgc Phap chia cac cong frinh kiln tnic d My Son ra lam 10 nhdm chinh: A, A',

B, C, D, E, F, G, H, K dl dat ten cho moi lang mg tiieo kieu ghep chii cai va sd'^'^l

4.3 Khu di tich Thanh Hoang De (Binh Dinh)

Thanh Hoang De nam tren dia phan xa Nhom Hau va thi trin Dap Da, huyen An

Nhan, tinh Binh Dinh each Tp Quy Nhom khoang 20km ve hudng Tay Bic Thanh

Hoang De dugc trieu dai Tay Som xay dung vao nam 1775 tren ea sd thanh Do Ban

(hay Cha Ban) eua vuang quoc Champa de lai va duge chinh thiic ggi ten la Thanh

Hoang D I tir nam 1778 Trong suot mgt thdi gian dai tir 1776 den 1793, thanh la dai ban

doanh cua quan Tay Som va sau do la kinh do cua chinh quyen trung uang Hoang De

Thai Diic - Nguyen Nhac''

Thanh Hoang De

nguyen la mgt tong the

kien tnic hinh chii nhat,

gom ba vdng thanh:

Thanh Ngoai, Thanh Ngi

va Tir Cam Thanh Thanh

Ngoai cd chu vi la 7400m

Thanh Ngi dugc ggi la

Hoang Thanh cd hinh chu

Hinh 7: Cong chinh Thanh Hoang Dk

370m Ben trong thanh ngi la Tir Cam Thanh ciing cd hinh chir nhat dai 174m, rgng

126m dugc xay theo hudng Bac Nam''^

Sau khi trieu dai Tay Son that bai, Thanh Hoang D I , danh diu mgt thdi vang son

eua Tay Son ciing bi do nat Tren nen cii cua thanh, nha Nguyen cho xay mgt khu lang

mg thd hai vien quan nha Nguyen da chet d day la Vd Tanh va Ngo Timg Chau Day la

mgt khu lang mang phong each my thuat thdi Nguyen nam trong quin thl di tieh''^l

Thanh Hoang de trong lich sii la nai khdi ngudn cua nhung euge xuit binh eua

nghTa quan Tay Som, dat nen mdng eho su thong nhat dat nuac va ea viec ehiing kiln

nhung su kien bi trang trong nhung nam thang cuoi ciia trilu dai ba anh em Nguyln

Nhac, Nguyln Hue va Nguyln Lir''^l

Sau khi nha Tay San sup do, thanh Hoang de bi nha Nguyln (Nguyen Anh) pha

buy Di tich thanh Hoang dl da dugc Nha nudc cong nhan va xip hang hi eu6i nam

1982''^l

Mac du bi nha Nguyen pha buy nhung nhung gi con sdt lai du de cho du khach tham quan thanh Hoang de tudng nhd mgt Vuang trieu Tay Som da lam rang danh lich sir dimg nudc va giii nudc cua dan tgc ta''^l

II Phuong phap phan tich kich hoat notron - NAA

1 Casavgtly

Moi mgt nguyen to ton tai trong tu nhien cd cac thong so dac tnmg nhu: Khoi

lugng nguyen tir {M), do pho bien dong vi (9), tiet dien bit natron (cr), v.v

Product Nuctoui

Cornpound Nuclcui

Del eyed Gamma ray

Ca sd ciia

phuang phap

NAA la dua

fren phan iing

hat nhan giira

vdi natron trong LPU, san pham tao thanh sau phan iing la cac ddng vi phong xa Moi

mgt dong vi phdng xa cd cac dac trung nhu: Hoat do (A), chu ky ban huy (T/zi), cudng

do phat biic xa (P^, nang lugng biic xa phat ra (Ef), v.v Bdi dong vi phdng xa la

khong ben nen cd khuynh hudng tim ve mgt frang thai can bang hom bang each phan ra

phdng xa Trong dd phan ra P' phat ra tia y la mgt trong nhung qua trinh bien doi hat

nhan tir frang thai khong ben ve trang thai ben Cac tia y phat ra trong qua trinh phan ra

cd nang lugng dac trung cho timg hat nhan Dimg mgt he pho ke gamma ta thu dugc phd gamma bieu dien su phu thugc giua nang lugng gamma va so dem Xir ly pho gamma nay chiing ta cd the xac dinh dinh tinh hay dinh lugng thanh phan cua cac nguyen to cd mat frong mau''*l

2 Phdn img hat nhdn

Phan ling hat nhan giu vai trd trung tam trong toan bg phuang phap phan tich kich hoat NAA Trong mgt phan iing hat nhan, khi mgt hat photon tdi (vd: Natron (n), Proton (p+) hay hat Alpha (a)) tuong tac vdi hat nhan bia se xay ra mgt trong hai hi?n

tugng hoac tan xa hoac hap thu Bieu do minh hga mgt phan iing hat nhan tieu bilu cua

qua trinh hip thu photon tdi duge dua ra frong hinh 8, va theo sau la su phat ra ca hat

tiie thdi va tia gamma tiie thdi de sinh ra hat nhan phdng xa (con ggi la dong vi phdng

xa) Mgt phan iing hat nhan cdn cd the mo ta bdi bieu thiic sau: ^

a + A->fX]->b + B+Q (1) hoac frong each vilt ngin ggn ed thl ky hieu nhu sau: A(a,b)B O day ky hieu a la chi

photon tdi, A la hat nhan bia, [X] la hat nhan hgp phin frong frang thai kich thich, B la

hat nhan san phim (thudng la hat nhan phdng xa), b la hat thii cip hoac la biic xa, va Q

tdng nang lugng giai phdng hay hap thu frong qua trinh xay ra phan ung Neu Q duomg,

phan ling dugc ggi la phan iing tda nhiet, Q am, phan iing dugc ggi la phan iing thu

nhiet Cac phan iing hat nhan dugc gay ra bdi eae nafron la loai phan ling tda nhiet, va

nang lugng ngudng qui udc la zero (0) Trong hau het eae iing dung eua phan tich kich

hoat natron, hat nhan san pham B la hat nhan phong xa va ehiing phat ra mgt hay nhieu

tia gamma tre Ky thuat dua tren viec do cac biic xa gamma fre dugc ggi la phan ti'eh

kich boat gamma tre (Delayed Gamma Neufron Activation Analysis - DGNAA) Thong

thudng DGNAA dugc ggi la phan tich kich boat nafron dung cu INAA (Intrusmental

Neutron Activation Analysis) Trong thu tuc phan tich INAA eae budc xii ly hoa nhu

tach, chiet, lam giau, v.v trudc va sau khi chieu xa la khong su dimg''l

3 Pho natron Id phdn ung vd tiet dien phdn img

Nhung 16 phan ung hat nhan van hanh fren ea sd phan hach nhien lieu ^^^U ngay

nay thudng tao ra ngudn nafron c6 cudng do lan va rit thich hgp cho NAA Phd nafron

frong 16 phan iing la dugc khdp tii 3 phan phan bo theo nang lugng eua nafron duge ehi

ra frong hinh 9 Trong vimg nang lugng cao, cac nafron van cdn phin ldn nang lugng

goc ciia chiing tir qua trinh phan hach (khoang 2-6MeV) va thudng dugc ggi la natron

phan hach hay 'natron nhanh\ Cac ncrtron nhanh nay mit nang lugng mgt each nhanh

chdng thong qua qua trinh tan xa dan hdi vdi cac vat lieu lam cham ben frong 16 phan

ling nhu la nudc va graphite Nhung nafron ed nang lugng tir 0,5-1 MeV thudng duge

ggi la 'natron tren nhief Su phan bo cua cac nafron frong viing nang lugng fren nhiet

la gin diing vdi qui luat l/E Nhung nafron cd nang lugng <0,5 MeV thudng dugc ggi

la 'natron nhiet\ Nhung nafron nhiet, mgt each gin diing, co van toe nhu nhau (v)

chiing phan bo theo phan bo Maxwell-Boltzman, co dang:

dn

dv Vl^jTI

i^^2^-(v/v„)^

(2)

Doi vdi 16 phan iing lam cham bang nudc nhe (nudc thudng), thdng lugng ncrtron

fren nhiet chiem khoang 2-3% va thong lugng nafron nhanh chiem khoang 7-10% so

vdi thong lugng natron nhiet Thong thudng dan vi ciia thong lugng natron dugc bieu

dien bang: cm'^s'

Khi ndi den nafron nhiet, thudng dugc qui udc rang van toe ciia nafron v~2200

ms'', nhiet do T„~2(fC, tuomg iing vdi nang lugng la E„~0,0253eV Dan vi ciia tiet dien

phan ling thong thudng dugc bieu dien bang barns (b), vdi lb=10'^'*cm'^

dien cho hau

het cac hat

nhan cd dac

trung la cac

T H t l M U MCUTTCMS

Watt tetribulion

dinh cgng fji^^ g p^Q ^^^g i^^j^g natron dac trung tir mgt LPU hat nhan

hudng nim tren dudng cong 1/v Cac nang lugng cgng hudng triing khdp vdi cac trang

thai kich thich ciia hat nhan hgp phin Dk thuan lgi frong viec tinh toan toe do phan img

tai viing thong lugng I/E, mgt tilt dien fren nhiet / (con dugc ggi la tich phan cgng

hudng hieu dung) dugc dinh nghTa bdi bieu thiic sau:

a(E)

Bdi vi ca hai loai nafron nhiet va fren nhiet deu cd the gay ra cac phan iing (n, y), ton tai

mgt do bit dinh, nhung each ph6 biin dimg de tinh toe do phan iing toan phan cho mgt

hat nhan bit ky cho bdi bilu thiic sau, vdi gia sir n la so nguyen tir ciia hat nhan bia cd

frong mau

• - • ' R = M„^.h^KJ} (4)

frong dd: ifhh va ipepi thong lugng nafron nhiet va fren nhiet Trong hau het cac trudng

hgp, tilt dien nhiet va tilt dien cgng hudng la cd ciing do ldn, nhung mgt s6 it trudng

hgp thi tiet dien nhiet lan hom nhieụ Vi vay, su kich boat gay ra bai nafron nhỉt dong

gdp mgt tong lugng boat do chu yeu eho hau het cac nguyen tố^l

Tai nhung miic nang lugng cao hom cua nafron, tiet dien ciia phan iing (n, y) la rit

nhd va nhung phan iing hat nhan ma frong do chiing giai phong ra mgt hay nhieu hat

nhu eae phan iing (n, p), (n, a), (n, n') vd (n,2n) cac phan iing nay dugc ggi la cae phan

ling nguong Nhung phan ung chuyen hda nay xay ra chi khi nang lugng cua nafron tdi

la vugt tren mgt ngudng nang lugng cue tieu Er yeu cau doi vdi timg phan iing cu the de

xay rạ Bdi nang lugng cua nafron phan bo kha phiic tap d vimg nang lugng cao, tiet

dien trang binh cho mgt ncrtron nhanh de xay ra phan iing la ay duac dinh nghia bdi bieu

thirc:

[ CT(E)(f>iE)dE Gf=^ (5)

l<l>{E)dE

Sii dung tiet dien tmng binh nay cho toe do phan iing toan phin doi vdi phan iing hat

nhan gay ra bdi norfron nhanh eho bdi bieu thiie:

O day: ^duge dinh nghTa la thong lugng nafron trung binh Chi ed mgt s6 it trudng hgp

ma nd ed đng gdp quan frgng frong NAẠ Trong nhiing trudmg hgp do, thudng ngudi

ta dung la do Niken vdi phan iing ^^Ni(«, ;^^^Co dk hieu chinh hieu iing gay nhieu eua

natron nhanh cho cae phan iing (n, y) cho mgt so nguyen t6 nhe (nhu Na, Mg, Al)''''*l

4 Lo phdn img hat nhdn Dd Lat

LPU tiep tuc la nguon natron chiem uu thl myet doi frong phuang phap NAA vdi

thong lugng natron ( ^ cao (~10'^-10'''n.cm^.s'')

LPU Da Lat duge ngudi My khdi cong xay dung frr diu nam 1960 mang ten

"TRIGA Mark II", dat frang thai tdi ban lan thii nhit vao ngay 26/2/1963 Ngay

4/3/1963: LPU Da lat chinh thiic khanh thanh vdi cong suit danh dinh 250kW Tir

1963-1968: LPU boat dgng vdi 3 muc dich chinh la huin luyen, nghien eiiu va san xuit

đng vị 1968-1975: LPU d ehi do dimg Ngay 15/3/1982: Vdi su giup da eua ngudi

Nga (Lien X6 cu), khdi cong cong trinh khdi phuc va nang cip LPU Da Lat va duge đi

ten thanh "IW-9" Ngay 20/3/1984: LPU I W - 9 chinh thire dugc khanh

'• i a i j <y •

thanh vdi cong suat danh dinh

500kW, vdi do giau bd nhien lieu

la 36% "^U Tir 1984 din nay:

LPU Da Lat boat dgng cho cac

muc dich san xuat ddng vi phdng

xa, phan tich kich boat nafron,

nghien ciiu ea ban, iing dung va

huan luyen nhan luc Hinh 10 la so

do tiet dien cat ngang cua LPU Da

Lat hien nay Trong do, cac kenh

chieu kho 7-1, 13-2 va 40 hoc

chieu udt fren mam quay LPU la

nhiing kenh chieu xa dugc sii dung

trong phan tich N A A ' ' ^ 1

5 Phdn rd phong xg

• Tianh A<n kbxo

Kcflb daeu cau 13-2 KahcteAimiu'-l V«it DIMB n Graate

3JM

Hinh 10: Binh do LPU Hat nhan Da Lat

Phan ra phdng xa la hien thugng chuyen hda tu phat cua nguyen tir qua viec phat

ra cac hat, tia gamma tir hat nhan, hoac tia X sau khi bat cac electron d lap v6 nguyen tir Qua trinh phan ra phdng xa la mgt qua trinh thdng ke Vi du trong mgt mau cd chiia mgt sd lugng ldn cac nguyen tir phdng xa, khong cd each nao de c6 the nhan biet trade nguyen tii nao se phan ra tiep theo Nhung dac trung phan ra toan phan cua mau phdng

xa cd the dugc md ta So nguyen tir phan ra frong mgt dom vi thdi gian dugc dinh nghia

la boat do A dugc dinh nghTa bdi nguyen ly co ban cua hoat do phong xa

A = = /UV

dt

(7)

d day, iV la so nguyen tii phdng xa frong mau va A la hang sd phan ra

Gia tri eiia A la khac nhau doi vdi moi loai phdng xa khac nhau Bieu thiic mo ta sir phu

thugc ciia sd nguyen tii phdng xa theo thdi gian nhu sau:

frong dd No la so nguyen tir phdng xa tai thdi diem t=0 Bdi vi qua trinh phan ra phdng

xa tuan theo qui luat ham mii ciia e va hoat do ciia chat phdng xa dugc kiem soat bdi

thugc tinh die trung d3 biet ciia thdi gian ban ra (chu ky ban buy - la khoang thdi gian

ma hoat do phong xa giam di mgt niia tinh tir thdi diem t=0) Thdi gian ban ra hen quan

din hing so phan ra A theo bieu thiie sau: * • t ''I> 'V' '•

hi 2 0,693 „>

Chu ky phan ra ciia nhiing hat nhan phong xa khac nhau la khac nhau va frai fren mgt

dai rgng tir mill giay (ms) cho din nhilu lin ldn hon tuoi eua vu tru ma chiing ta dang

song

Trong NAA su dung cac tia gamma fre, so cac nguyen di phan ra frong suot

khoang thdi gian sau chilu xa (kich boat) la dugc xac dinh So nguyen tir phdng xa co

mat frong miu tai mgt thdi diem bat ky (sau khi kich boat) phu thugc vao so tong cac

nguyen tu phong xa dugc tao ra frong suot qua trinh chieu xa va lien tue giam dan tir

thdi diem ket thiic chieu cho den khi bat dau do Do do, toe do cua qua trinh kich boat

(toe do phan ung), chu ky ban ra, thdi gian chieu (Tj), thdi gian ra (T4}, va thdi gian do

pho (Tc) la nhimg tham so rat quan trgng frong NAA

Ve mat toan hgc, toe do ciia su thay doi cua so nguyen tir phdng xa trong suot qua

trinh chieu xa la hieu so giua toe do phan iing va toe do phan ra nghia la:

dN

^ = R-m (10)

dt Gia su rang, khong cd nguyen tir phdng xa nao co mat frong mau tai thdi dilm t=0, thi

so nguyen tir phdng xa cd mat tai thdi diem ket thiie chilu (End of Irradiation-EOI) se

la:

Nso,=j(\-e-'') (11)

Thong thudng, viec do biic xa phat ra hi mgt miu phdng xa khong bit diu ngay

tiic thi sau khi chieu ma phai dgi sau mgt thdi gian phan ra nhit dinh Trong dilu kien

binh thudng, thdi gian ra nay la ngan ddi vdi cac hat nhan phdng xa cd chu ky ban ra la

ngan va thdi gian ra la dai doi vdi cac hat nhan phong xa cd chu ky ban ra dai Bilu thiie

mo ta sd nguyen tir phdng xa ed mat tai thdi diem bit diu (SOC) va kit thiic (EOC) do

tuomg ling la:

Nsoc-N,„e-''^ =^{\-e'''')e-''^ ^j2j

va N,^, = N,„,e-''^ (1 - e"^^') = f 0 - ^ " ' ' ) ^ ^"''^ ( 1 " ^"''^) (^V

6 Sa do phdn ra vdpho ke gamma

Trong NAA, cac nhan phdng xa thudng phan ra ve cac nhan con chau (daughter)

bang each phat ra cac hat be-ta (P) trade khi ve frang thai ben Cac nhan con chau dugc

tao ra thudng la d trang thai kich thich va phat ra mgt hay nhieu tia gamma trudc khi trd

ve frang thai ben Do cac tia gamma nay bang cae he pho ke gamma, chiing ta se thu

dugc nhiing thong tin can thiet de xac dinh ham lugng ciia nhiing nguyen td trong mau

chieu xa

Sa do phan ra ciia cae nhan phdng xa sap xep tir dom gian den phiic tap Mgt so do

dom gian duge minh hga bang phan ra ciia ^*A1 (/7/2=2,24phiit), nd dugc tao ra bdi viec

chieu xa ddng vi ^^Al Nhan ^^Al phan ra P' de ve miic kich thich 1779keV ciia nhan con

la ^*Si Trong trudng hgp nay, viec dich chuyen tu trang thai kich thich ve trang thai ben

nhan ^^Si luon luon phat ra mgt tia gamma co nang lugng 1779keV vdi hieu suat phat la

100% Nhiing sa do phan ra cua cac nhan phdng xa khac la phiic tap hom nhieu

Tia gamma tuomg tac vdi vat chat theo nhieu each, mgt trong so do la qua trinh

hap thu ma nang lugng ciia tia gamma tdi la dugc trayen cho cac phan tir quang dien

(photoelectons) ben trong chat ban dan cua dau dd (detector) Thong thudng, nang

lugng ciia gamma phat ra tir cac mau dugc chieu xa bdi natron trai rgng den 3200keV,

tao nen mgt pho gamma dac trung ciia mau

Tren thuc tl s6 tia gamma dugc thu nhan bdi dau do HPGe dimg cho viec tinh

toan ham lugng cac nguyen to la nhd ban nhieu so vdi so tia gamma tong phat ra tii

miu, chiing phu thugc vao nhilu ylu tl khac nhau: (i) Cudng do phat gamma trong

nhilu tradng hgp la nho hom 100%; (ii) Mgt s6 tia gamma phat ra thu mau nhung khong

din duge diu do Tiiy thugc vao tinh chat tu nhien dang hudng (khong cd hudng uu

tien) ciia qua trinh phat xa tia gamma, chi nhung tia gamma nam trong 'goc nhin' cua

diu dd thi c6 thl do dugc; (iii) Mgt so tia gamma se di xuyen qua dau do ma khong cd

bit cii su tuang tac nao, dac biet doi vdi cac tia gamma cd nang lugng cao Trong mgt

sd tradng hgp khac, mgt phan nang lugng ciia tia gamma bi mat bdi tan xa Copmton va

hieu ling tao cap, theo each do chiing se dong gdp vao nen phong lien tue dudi vimg

dinh quang dien quan tam Yeu to (ii) va (iii) lien quan den dac trung ciia dau dd, dugc

ggi la hieu suit hinh hgc £ Tir viing nang lugng 200keV trd len, 16-ga-rit eua hieu suat,

mgt each gin diing, nhu mgt ham myen tinh doi vdi 16-ga-rit cua nang lugng

log£ = b\ogE^+loga "'"•' (14)

d day, cac hing so a va b phu thugc vao khoang each tir miu din diu dd va kich thudc

cua tinh the chat ban dan ben frong dau do

Cd nhilu ky tiiuat dl nit ra eae thong tin vl dinh tinh va dinh lugng tir pho

gamma Tir mgt phd gamma tiiu dugc, nhiem vu trade tien la nhan dien cac hat nhan

tuomg ling vdi cac dinh nang lugng khac nhau (dinh tinh) va rihiem vu thii hai la xac

dinh dien tich cua cae dinh nang lugng do (dinh lugng) Viec nhan dien dinh ed the

dugc thuc hien vdi su frg giiip eiia cac tai lieu lien quan nhu sa do phan ra, bang liet ke

nang lugng gamma va ti so re nhanh Doi vdi hau het eae dinh, dien tich dinh (hay con

ggi la tin hieu) co the dugc xac dinh bang viec lay so dem tong cgng dudi vimg dinh va

trir di so dem phong nhu sau:

S=T-B (15)

Tuy nhien, trong tradng hgp cd nhieu dinh chong chap, thu tue khdp dang dinh

Gauss thudmg dugc sii dung de xac dinh dien tich cua cac dinh rieng le Hoat do eua

mau thu dugc bang viec chia dien tich dinh cho thdi gian do (TJ

Do khong chac chan do ciia dien tich dinh dugc xac dinh bang viec tinh do lech

chuan tuomg ddi theo dom vi phan fram (%) Cach tinh do lech chuan thong thudng duge

dimg cho bdi bieu thiic:

%s.d = (100^JS + 2B) IS (16)

Gidi han phat hien (Limits of Deteetion-LOD) doi vdi mgt dinh phu thugc vao

chat lugng ciia viec xac dinh so dem phong Dinh nghTa thudng dimg eho gidi ban phat

hien la fren ea sd xac suat do tin cay tai 2a (-95%) eua dien tich dinh tren nin

phong"''^'

7 Tinh hdm lucmg

De tinh ham lugng ciia mgt mau hi boat do do duge eo thl su dung phuang phap

tuyet ddi ma qua do tat ca cac kien thiic va so lieu hat nhan va cae thong s6 thuc nghiem

la can thiet, cung nhu bieu thiic ve boat do co mat trong miu tai thdi dilm bit ky la

dugc dimg

A = \ ^N,ey„cT„+<l>J)P^sSDC (17)

a day: m = khdi lugng miu (g), M = khoi lugng nguyen tu (g mol'), NA = S6

Avogadro (6,02 x 10^^phdn tic mol') 6= do phd biin đng vi (%), Py= cudng do tia

gamma dugc do (%), £ = hieu suat cua dau đ tai nang lugng tia gamma dugc do, S =

he s6 chilu (l-ê\ D = he so phan ra (ế^') va C = he s6 do (1-ế^')

Tuy nhien, phuang phap tuyet đi hiem khi dugc dimg trong khao c6 ma phuang

phap chuan h6a so sdnh thuang duge su dung nhilu hom Bilu thiic dimg dl tinh toan

ham lugng cua nguyen to quan tam frong mau can phan tich lien he vdi ham lugng da

biet frong chat chuan so sanh frong phuomg phap so sanh nhu sau

Aạ _m.an,i^-''')

a day, A = boat do ciia mau (sam) va chuan (std), m = khoi lugng ciia nguyen td quan

tam va Td = thdi gian phan rạ Khi thuc hien mgt phep chieu ngin, cac tham so thdi

gian chieu, ra va do ciia mau chuan va mau phan tich thudng la gidng nhu nhau (cd

nghia la cac budc frong thu tuc phan tich dugc thuc hien tren timg mau va chuan rieng

le mgt each tuan tu va tat ca dugc do vdi cimg mgt hinh hgc) va nhu vay, cac thong so

phu thugc thdi gian va hinh hgc do se bi triet tieụ Do đ, bieu thiic (18) se chi cdn

W A

"sam ^sld

a day, C = ham lugng cua nguyen to frong mau va frong chuan \k W = khoi lugng ciia

mau va chuan

Hau het cac phdng thi nghiem NAA deu cd sii dung mgt hay nhieu chat chuan da

nguyen to frong qui trinh phan tich Thu tuc co ban de ghi nhan pho gamma doi vdi mau

va chuan frong nhiing dieu kien tuomg tu va cang giong nhau cang tot Tir nhiing dinh

gamma dac tnmg cd mat frong pho va bieu thiic (19) ngudi ta co the tinh ham lugng ciia

nhung nguyen to frong mau phan tich

Ngay nay, ngoai hai phuang phap neu fren, phuomg phap chuan hda ko-NAA la mgt

phuang phap chuan hda hien dai dang dugc rat nhieu PTN NAA tren the gidi quan tam,

nghien ciiu va ap dung ko-NAA dac biet chiem uu the frong cac bai toan nghien ciiu doi

tugng cu the ma mau khao eo la mgt dien hinh Phuang phap ko-NAA la ket qua tich

hgp CO cai tiln va chgn lgc cua hai phuang phap neu fren va phuang phap chuan dom,

vdi cae uu dilm: (i) Dom gian nong thuc nghiem (so vdi phuomg phap so sanh), (ii) Do

chinh xac cao (so vdi phuang phap myet doi), (iii) Cd tinh linh boat (so vdi phuang

phap chuin dom), (iv) Thich hgp frong qui trinh xu ly tii dgng (may tinh hda) He so ko

dugc dinh nghTa nhu sau:

Ham lugng ciia nguyen to frong mau dugc xac dinh theo cong thiie:

(^,IT^

^^SDCW]^ 1 g, -/ + g -go.JQ^) ^., ^21)

Ap.m ' Km ( « ) ' G„^a • / + G,,a •Qo.a ( « ) ' ^p.a

d day, p = ham lugng nguyen to quan tam a (ppm, lppm=10'^g/g), Asp= toe do dem

rieng, m= la dd thong lugng ncrtron,/= ^//^e, ^/,= thong lugng norfron nhiet, (f>e= thong

lugng natron fren nhiet, Qo=Io/cro, G,h va Ge la he sd tu che chan nafron nhiet va tren

nhiet, a = he so lech pho norfron khdi qui luat l/E, £= hieu suat ghi eua dau do biic

xa"'^l

De kiem soat qui trinh phan tich (Quality Control - QC), thong thudng mau chuin

tham khao duge chiing nhan (Certified Reference Materials - CRMs/Standard Reference

Materials - SRMs) dugc chieu kem trong tung loat mau phan tich mgt each dgc lap

nham de kiem tra chat lugng cua ket qua va nhan dien cac loi cd the eo frong qui trinh

i n X u ly thong ke da bien

Cac phuang phap phan tich thong ke da bien da dugc ap dung rit rgng rai frong

nhieu nganh khoa hgc ky thuat khac nhau nhu: Moi trudng, dia chit, khao e6, y hgc,

sinh hgc, hoa hgc, vat ly, luat, thuang mai, v.v Trong khao c6 hgc, s6 lieu khao sat

bang cac phuomg phap phan tich la ca sd dir lieu ve ham lugng da nguyen t6 (-30

nguyen to) trong mgt tap hgp miu nghien eiiu Ca sd dii lieu nay ham chua nhilu thong

tin dac Uimg cho nguon nguyen lieu lam ra chiing nhu: Thanh phin cae nguyen td chinh

dai dien cho mgt nguon nao do, mgt lap mau nao do, v.v su gidng va khac nhau giira

cac nhdm miu ve nguon gdc, xuit xii, vl thdi dai hay dugc tao ra tir eae cong nghe khac

nhau, tir nhiimg tgc ngudi khac nhau frong qua khii Tuy nhien cac s6 lieu do hay quan

sat dugc thudng d dang da chilu (multidimension data), (ham lugng cua mdi nguyen td

frong mgt tap hgp miu dugc ggi la mgt vecta quan sat va doi vdi khoang 30 nguyen to quan sat dugc, chiing ta se c6 tuomg iing 30 vecta so lieu khac nhau) De cd the danh gia

va thu dugc cac thong tin co y nghia, chiing ta can su dung cac phuomg phap xir ly thong ke da bien fren tap so lieu thu dugc tir phep phan tich tren tap cac mau da chgn Trong cae nghien ciiu khao co, hai phuang phap thong ke da bien dugc sir dung phd

bien nhat trong viec xu ly so lieu phan tich la: Phep phdn tich cdc thdnh phdn chinh PCA vdphdn tich nhdm - CA

-1 Cdc buac ca bdn trong xir ly thong ke da Men so lieu:

(1) Chuan hoa bg sd lieu, each thong thudng bg so lieu dugc chuyen ve thang

16-ga-rit CO so 10 Muc dich ciia viec lam nay la de giam thieu su chenh lech qua Ion ve

ham lugng gitra cac nguyen td (% va ppm)

(2) Quy doi cau tnic bg so heu ve dinh dang chuan, budc nay nham tao ra file input chuan de c6 the sir dung cho nhieu chuong trinh xir ly thong ke khac nhau, dong thdi giiip quan ly, cap nhat dii lieu va ban che su nham lan

(3) Phan tich da bien bang cac chuomg trinh xu ly, sii dung cac phuomg phap xir ly (PCA, CA, V.V ) phii hgp da chgn Budc nay nham lam giam so chieu cua bg du lieu

ma khong lam thay doi tinh chat tuomg quan thong ke cua chiing

(4) Nhan dien cac cau tnic nhom, nham tim ra moi tuomg quan giira cac nguyen to, cac nhom mau frong bg du lieu So lieu co the dugc bieu dien dudi dang do thj nham lam ro cac moi tuomg quan hoac do lech cua so lieu so vdi ti so tuomg quan Hoac sir dung cac bieu dien phan bo de nhan ra cac so lieu bat thudng Moi tuomg quan giua cac s6 lieu nay cd thl cung cip nhiing thong tin co gia tri nham danh gia thong ke so lieu va tim ra cac nhom phan bo rieng biet ciia mau vat, tir do co the nhan biet dugc nguon goc ciia chiing

(5) Danh gia xac suit hay kha nang cua dii lieu la thanh vien ciia mgt nhom nao dd hay khong

S6 lugng miu tdi thilu dl dam bao mgt ket qua phan tich da bien dang tin cay dugc tinh thong qua bac tu do Bac tu do ciia s6 lieu dugc cho bdi cong thiic: N-1-(V-l)/2 Uong do N la so tradng hgp va V la s6 biin S6 bac tu do toi thieu la 30, ly tudng la

60 hoac nhilu ban, nhu vay so miu toi thieu cho 1 bg so lieu la khoang 15 mau'''

2 Phuang phdp phdn tich thdnh phdn chinh PCA

Phep phan tich PCA la mgt trong nhung ky thuat xu ly s6 lieu da chilu quan trgng nhat duge sir dung frong khao co hgc va nhieu linh vuc khoa hgc khac Phuang phap nay cho phep chiing ta gian thieu dugc dang ke so chieu ciia tap so li?u bing each lap eae to hgp myen tinh tir tat ea cac vecta quan sat de hinh thanh mgt so vecta so lieu mdi

ed do nhay cao nhat doi vdi sir thang dang thong ke hay cau tnic eiia tap so lieu Cae vecta so lieu mdi nay dugc ggi la cac thanh phan chinh PC (Principle components) Tir eae he so to hgp myen tinh chiing ta se xac dinh dugc cae thanh phan nguyen to chinh

va moi mang quan dac trung giiia cac thanh phan chinh nay Cae tuomg quan dac tnmg khac nhau se dai dien cho cae nhdm mau c6 nguon goc xuat xii khac nhau Ngoai ra, ehiing cdn c6 the loai bo su anh hudng eua cac thanh phan nguyen to cd frgng so tuomg quan thap va gay phan tan (nhieu) trong qua trinh xu ly so lieu ma khong lam mit dang

ke lugng thong tm ehiia tiling ke eiia tap s6 lieu Thanh phin chinh tach ra diu tien (PCI) bao gom mgt so lugng ldn nhat cac phep biin doi tdng va ed mdi quan he myln tinh vdi cac biin ban diu Thanh phin chmh thii 2 (PC2) chiia dung phin ldn cac phep bien doi cdn lai va cd tinh chat true giao vdi thanh phin chinh thii nhit Thong thudng, cac tuomg quan nay dugc mo ta bdi 3 tiianh phin chmh diu tien (PCI, PC2 va PC3) vdi xac suit khoang 70% hoac han''^'^"l

- Chudn bi sd lieu ban ddu

So lieu ban dau (origin data) la so lieu ve ham lugng cua p nguyen td frong n

mau, can chuan bi dudi dang mgt ma fran A(n,p); n dugc ggi la s6 chilu eiia vecta quan

sat (so miu phan tich), p la so bien iing vdi mdi vecta (s6 nguyen td)

- Xdc dinh cdc tri rieng vd vecta rieng cua ma trdn S

Tri rieng va vecta rieng e6 till duge xac dinh bing each giai phuang trinh sau:

(S - /ll)x = 0

X la ma fran vecta rieng

(24)

X la cac tri rieng (ma fran cgt)

I la ma tran dom vi

|A - >il| = 0 —»^ xac dinh dugc A —• thay A vao bieu thiic tren se xac dinh dugc x

- Xdc dinh cdc thdnh phdn chinh (PCA)

Cac thanh phan chinh yj dugc xac dinh nhu sau :

yj = (Xji,Xj2,Xj3, Xjp) (ai,a2, a3, ap) = 2^Xj,a, (25)

yi = xuai + Xi2a2 + xuas + + xipap

yi = X2iai + X22a2 + X23a3 + + X2pap

y3 = X3iai + X32a2 + X33a3 + + xspap y4 = X4iai + X42a2 + X43a3 + + X4pap

yi va y2 la thanh phan chinh thii nhit (PCI) va thanh phin chinh thii hai (PC2) ciia tap

so lieu Ti le giai thich dugc su thang giang cua so lieu tuomg iing vdi moi thanh phin

Khi p=2 thi true chinh cua hinh ellip di qua diem (a, ,02) va gdc xoay true toa do la

ai2/aii; ban kinh true ldn va true nho ti le vdi VAI va VA2 tuomg iing

- Chon lua sd cdc thdnh phdn chinh

So lugng cac thanh phan chinh can giu lai dugc chgn theo mgt trong hai quy tac sau:

a) So lugng cac thanh phan chinh dugc chgn sao cho gia tri tich Idy ciia ti le P

cua cac thanh phan nay la > 80%

b) Ti le P cua thanh phan nho nhat dugc chgn phai > gia tri trang binh

• y j ^ [19,20]

3 Phucmg phdp phdn tich nhom CA

De xir ly mgt so lugng ldn cac dtr lieu, phuomg phap phan tich nhdm thudng dugc

sir dung Day la budc tiep can dau tien nham xac dinh lieu cd ton tai hay khong cac

nhdm mang y nghia thong ke Phep phan tich dua tren viec xii ly cac ma tran khong

dong nhat cho tit ca cae cap mau kha di bang cac phep do 'khoang each' - phuomg phap

m6 ta sir "gan" nhau giiia cac mau (dugc coi la cac diem) trong khong gian ham lugng d

thang 16-ga-rit Mgt so phep tiep can thudng dugc su dung nhu: (a) khoang Euclidean

chuan, (b) khoang Euclidean binh phuang, (c) khoang EucUdean binh phuang tnmg

binh, (d) khoang Euclidean trung binh Ket qua viec phan tich nhom dugc bilu dien bdi

cac dendogram cho thay thii tu cac mau ket nhdm vdi nhau va khoang each giira chiing

Day la phuang phap dan gian va hieu qua de nhan dien cac nhom Trong do moi nhdm

eon chiia cac miu co su tuomg tu cao (high similarity) nhung lai eo su khac biet ldn

(very dissimilar) doi vdi cac mau tir cac nhdm khac'' '^ '^ \

- Tinh khodng cdch (Euclidean distance) giira cdc mdu vd giira cdc nhom

Ham khoang each {Euclidean distance) giua hai vecta di = {a\, al, , ap)\di

2L' = (a'\,a'2, , a'p) duge dinh nghTa nhu sau:

d{a,d)^f^(,a.-a'.f (27)

Khoang each gitra hai nhdm mau A va B duge dinh nghTa la khoang each nhd nhat giua

mgt diem (vi tri) thugc A va mgt diem thugc B

D(A, B) = min{c/(^a,, Hj); a, thugc A vd aj thugc B}

- Thiet lap cdc nhdm ban ddu

Dat n nhdm ban dau momg iing vdi n miu, moi nhdm chiia mgt miu Sau do tiln

hanh tinh ma tran khoang each DM (Distance matrix) gitra tit ea cac nhdm ban diu nay

- Thuc hien cdc vdng lap bdng phuomg phdp "Single Linkage"

a) Tim trong ma tran DM, hai nhdm nao cd khoang each nho nhit thi kit hgp lai

vdi nhau thanh mgt nhom Ghi nhd lai do ldn ciia khoang each cue tilu nay

Nhu vay so nhdm sau moi budc lap se giam di 1

b) Tinh toan lai ma tran khoang each DM cho tit ea cae nhdm con lai + nhdm

mdi

c) Lap lai budc 3 cho din khi chi eon lai duy nhit mgt nhom ldn chiia tit ea cae

nhdm con

- Ve so do hinh thdnh nhdm (Tree diagram hay con goi Id dendrogram)

Sa do dendrogram mo ta cac budc trong qua trinh hinh thanh nhdm a buac 3 va

cd gia tri thudc do khoang each tai cac vi tri ma cac nhom eon hoac cae miu duge kit

hgp thanh cac nhdm chinh

- Chon lua sd nhdm

Tir sa do Dendrogram, s6 nhdm phii hgp nhit tiiong thudng dugc chgn tiieo hai

each sau:

a) Cat ngang cac nhanh cua so do tai vi tri ed khoang each thay doi ldn khi cac

nhdm dugc ket hgp

b) Chgn so lugng cac nhdm tang hoac giam dan cho den khi thoa man bat dang

thiic sau:

CCj>CC^ks^^ J = l , 2 , , n , (28)

ai, a2, , a„ la cac gia tri khoang each tai cac vi tri ma n, n-1, , 1 nhdm tuomg

ling dugc tao thanh a gia tri trung binh, Sa la do lech chuan, va k la mgt hang so

(k= 1.25, dugc gidi thieu bdi Milligan va Cooper)''^'^""^''

IY Luu do qui trinh nghien ciru nguon goc vat lieu khao co dat nung bang phuong phap phan tich NAA va thong ke da bien

Khao sat vimg nghien eiiu

, -i::- J

Set nguyen lieu

(Qui trinh lay mdu)

Do tao tac dat nung

(Phdn logi, md hda)

Lap ho so mau, ma boa

(Vi tri, do sdu, nien dgi, v.v )

Chuan bi mau, Luu mau

(Theo phucmg phdp sir dung, INAA, XRFA, v.v ;

Phan tich mau

(Qui trinh phdn tich)

I

Dii lieu dau vao file Input

(Chuang trinh xir ly)

Xir ly thong ke

(Chudn hda sd lieu, PCA, CA)

Dii lieu dau ra

(File sd lieu, hinh ve, ddc trung hda cho cdc vimg nghien ciru, ddi

tuang nghien ciru)

Giai doan va bao cao ket qua

(Cdc nhd khdo cd)

Lmi trir

(Co so dir lieu)

Hinhll: Qua trinh cac budc frong nghien ciiu ngudn gdc

Phan 2

THLTC NGHIEM

I Thu thap mau

Trong nghien ciiu nay chiing toi da tien hanh thu thap hom 250 mau tir 3 khu di tich, bao gom: 73 mau dat set nguyen lieu, 102 mau gach cd, 69 mau manh gom co, 12 mau ngoi c6 va 6 mau gach hien dai Trong do, mau dat set nguyen lieu dugc lay d do sau tir 20cm den 130cm tiiy theo vi tri, tap trung tai Canh dong bay mau (dien tich: 36,9km , each khu di tich Quang Ngai khoang 700m (theo dudng chim bay) va khoang 2500m (theo dudng suoi V20) ve hudng Tay Bac) doi vdi khu di tich Cat Tien;

Khu Ao vuong (dien tich:

l,7km^, each khu di tich My

Som khoang 2700m (theo

dudng chim bay) va khoang

3000m (theo duong bg) ve

hudng Tay Bac) doi vdi khu di

tich My Som; Va Canh dong cai

tao Nhan Hau (dien tich:

5,0km^, each bd Thanh ngoai

khoang 800m (theo dudng chim

bay) ve hudng Ddng Nam) cho

khu di tich Thanh Hoang De

Ddi vdi mau gach co dugc thu

thap tii hiu hit tai cac tiiap, Hinh 12: Mo ta phuang phap liy miu dat set

nhdm thap frong 3 khu di tich vdi tit ca cac kich thudc dac trung Mau gom dugc thu thap rai rac frong khu di tich va tu cac hi khai quat H6 so miu dugc dua ra trong phu luc 3

MIU sau khi dugc thu tiiap, chuyin vl phdng thi nghiem, dugc ma hda, phan loai va tien hanh lam mau