f- srl HINH THAiH rdr ru cARBoNAT TRoNG TRAM ricu TAr cuAu rnd soNc oAlr r_AY cuu rrNG m x;AN rrrurax r DAr vAv oE u vAu vA pHUoNG pHAp psAN rrcn Di6n ph6n bd cIa kdt tu carbonat hach carbonat trdm tich cl6y vinh B6c BO Tai ddng bang sOng Cfru tong, c6c trdm tich carbonat tre (tudi Holocen) hdu nhu rdt han che Phuong ph6p phan tich Rfta sach lop bDn s6t bao quanh m6u, dd kho tu nhi€n Miu dd phan dch gdm mau kdt ru carbonat vd mAu bDn s6t mOi trudng bao quanh cring chic, kh6 bi x6i mdn hon ndn bin c6t bao vi c6 phiin ring v6i dung dich HCl C6c ket quanh m ldr que Thdnh phdn hoa hoc Kdt qui phAn tich cho thdy su kh6c bi€t 16 gifa thinh phdn ho6 hoc cria ket tu vii ciia lop bin s6r bao quanh (bdng vio nhtng rhdi gian kh6c rhuoc Id.hinh th0ng Holocen Du6i day ld mOt sO kdt qu6 phan tich thirih phAn vAt chdt cria k01 ru ndy 54 I) Quan sdt du6i kinh hi6n vi - Qu?n s6t l6t m6ng du6i kinh hidn vi phAn cuc cho th{y tr€n ndn ximang ho6 b6i vi tinh thti carUo_ Bdng l vi Thinh phdn ho5 hgc cia k6i tg carbonat tr$m tich bao quanh Oxyt, nguyen td At A2 26,64 38,95 Oxyt (%) si02 Al2Or q57 Tio2 0,38 3,26 Fe KzO MnO PzOs 0,6'7 Mgo CaO MKN 5n ?? 6,r3 r 22,89 PhAn tich RX microsound 8,87 0,76 5?O 4,1I l,95 20,30 n?? Hdm ludng khoAng carbonat thO hi€n su kh6c biet rO gifia thinh phAn khoAng vAt cria kOi tu vi lop bnn bao quanh Bidu cld RX (hinh,1) cho ph6p x6c dinh khoing carbonat chri yeu ld calcit gidu magne Hon niia, kdt quri phAn tich RX ciing nhu microsound (hinh 2) ddu cho thdy su phd bicn 1,22 0,M kho6ng sulfur thdnh phAn kOt tu carbonat 0,75 19,69 0,06 0,35 3,36 0,96 0,42 1,17 0,88 3,38 22,38 0,29 Na2O 1,87 2,0r TV THAO LUAN Nguy€n t6'(ppm) Sr Cu Co Ni Ba Cr Zn bidu hien phan lop d6i md nhat, nhung quan s6t chi tict mfrc ph6ng dai lon l4i khOng co ddu vet tan tich sinh vAt ; chfing t6, kct tu carbonat khong phdi ld tdn tich cfia srnh vAt da bdo 507 8528 t9 l5l 45 42 544 93 l0 18 162 35 35 1'7 42 289 103 80 A,1 - mAu ket tu carbonat Cam 49, A2 - mdu ket tu carbonat ven bidn Go COng - Tidn Giang, B - mAu trdm tich bun s6t bao kei tu A, nat bao c6c tAp hgp vi tinh thd khoang plrit d:n-e cdu vd tinh thd thach anh C6c tinh thd thach anh sic canh vd bd mit c6 nhidu vet xu6c qui trinh dich chuydn dong chdy Kien trfc ciiakettu c6 Su khic biet v€ phdn ho6 hoc, ddc bier le hem luong c6c nguy0n tO c6 ngudn gOc chinh ld vAt li€u phD sa s0ng Cfru [,ong [21,25] nhu Al, Ti, K (bdn7 2) lai thdp c6c kdt tu lUeing 1) chrmg t6 c6c kei tu niy hinh thdnh tai ch5 qu6 trinh trdm tich Luong m{t nung (MKN) cao ld dac tgng cho c6c trdm tich carbonat Hdm luong phOt ph6t cao hon chrit it chirng t6 su hinh thinh cAc ket tu ndy c6 liOn quan t6i hoat dOng sinh ho6 qu6 trinh trdm tich Tuy nhien, cdu tr(rc vi tinh thd quan s6tdudi kinh hidn vi phAn cuc vd hidn vi cliOn tu cung nhfrng kOt qui phAn tich nOu trOn, chfing t6 su hinh thinh c6c kOi tu ndy li0n quan tdi hoat dOng cua vi khudn Su c6 rnat cria c6c kdt tu m6i truon_e khri tuong deii kh6p kin cfing chung 16 c6c k€l tU niv kh6ng IiOn quan tdi bun carbonat dd phit hien trOn ndn da1'r'ung thdm luc dia [13] Ca - calch giau magne O - thesh anh Ca K, ch - kacllnlt ve chlorlt Sm - Emeclit lt - lilh h - hallt P - pyrll ca ca " I Ca )' tiii lii\ i' 16 21 32 ,rc Hinh I Bidu dd Ronghen k€i tu carbonat 48 vi o il QP 50 o2e CuKo trdm tich bao quanh 55 Bdnc Thtnh phdn ho5 hgc cfra phit sa vi trdm tlch v0ng cfia s6ng C&u Long [25] Oxyt, nguyOn to Hdm luong phan ye'u id kidm so6t q ha't to kh&i (earlY Qud ong nhilng bion rinh u6i bd mlt Oxyt (%) 65,48 -',l1,52 sio2 13,43 - 11,87 0,77 - 0,69 5,10 - 4,65 1,94 - 1,88 0,78 - 0,89 1,38 - 1,34 0,35 - 0,44 0,08 0,1l - 0,09 1,32 - 4,94 Al2o3 Tioz Fe203 &o Na2O Mgo CaO MnO PzOs MKN kh6i qu6t qua c6c Phan ung zC}rlzo + 89 19 Ni Cr 7l - Zn 66 -76 su tham gia cfra (nh6m Desulfovibrio) sulphat kht c[ng v6i X.RAY Live: Real: +9HCo, vi khudn khr] s s (l) Q) +6Hzo 9CH2O + aSO]- + 4FeOOH -> 4FeSlsv + 7'.1 Bemaining 100 s Preset : 100 13% Doad 115 H- d6 CH2O thd hien cho chdt hfu co, FeOOH vtin giAu tdm tich song Cuu Lnng [25] Luong Fe2* duo c gi6i ph6ng sE ket hqp v6i HS t4o sulfur sit It+, 22].T6ngh9p phin ung (l) vd (2) ta c6 : Kdt qui nghien c(ru cfra tl0l da chfmg t6 su hinh thenh kdt t&a carbonat (dolomit) didu kien HS + 2HCO, + -+4Fe2*+HCO; -92 -27 t4 30-36 Sr + 4FeOOH + CHzO + 7H* -> Nguy€n t|'(ppm) Cu Co SO]- : +H*+6H2o (3) Kdt qui phln (rng (3) s0 ldm tang hdm luong HCO; nu6c 16 r6ng vi gAy tria carbonat canxi hoac magne Nhu vAy, c6c kOt tu ndy dugc hinh ftanh qui rinh bien chdt so kh&i Qu6 lnh ld qu6 g trAm tich tich tu kOt carbonat le ph6 bidn mOi trudng trdm tich bi khrl ddm lAy, vfing vinh ven bidn & ddng bing sOng n€n hdu Crlu [ong Nhung on Ca2*, ng kin, kh6p nhu cho han ydu tri Mg2* lchir vd ngot c0 lAp bi ldy dAm trudng moi frong nhu ho6 ddn (thudng c6 thim phii thuc vet ret phet tridn) thi ktri neng tich tu carbonat cang thdp : Ca Sq kh6c bigt tudng ttdi v€ him luong cfra Mn vd Sr, Co, G,7^ gittacilc kdt tu A1 vd Az c6 lE lien quan t6i tli0u ki-en, toc dQ kdt tinh cria calcit vd ban ;l alcr P Ti _ :fl Mn,Fe MN 6.000 KeV FS=4K ch 610= 69 cts MEMl: 51P3 M4 SPECTRE Hinh Bidu d6 phln tich microsound tron l6t m6ng cria kdt tu carbonat 56 th0n ndng tlQ c6c nguy0n td niy cing Ca nu6c 16 n6ng moi trudng trdm tich 120,261 Him lugng nrong ddi ktr6c biet v€ Mn cdn phu thu0c vio diEn thd oxy ho6 khfi vdn li0n quan mlt thiCt voi toc trdm tich vd ndng cfia b€ mat phAn c6ch nudcftrlm tich Trong mOi trudng nu6c bidn, & didu kign co thd oxy ho6 khrl mqnh c6c tAn^g trdm tich sau, Mn+ nhanh ch6ng bl khir thenh Mn2* c6 mrlc dQ di tlOng cao hon [16] Do d6 ndng d0 ion Mn nu6c 16 r6ng cfing kh6c vi vi thO ndng dQ hdp thu lOn tria carbonat cilng kh1c' Mat khec, c6c kim loai ning kd tren cdn dr.roc tich lu! cung vdi kho6ng pyrit qfa trinh pyrit ho6 c6c hqp chdt sulfur [19] von c6 mit mAu phan tich (hinh I vd 2) Vi vay, mat d0 kho6ng pyrit kh6c gifia c6c m6u cflng g6p phdn ldm tang to kh6c bi0t d6ng kd vd n6ng dO cfra c6c nguycn td kim lo4i nang Do cing hi0n diOn v6i c6c kho6ng sulfur nOn c6c tich tu carbonat dE bi ph6 huy' mOt c6c kholng chfa lrru huynh niy bi oxy ho6 gAy chua ho6 m6i truong Do d6 c6c tich tu carbonat hdu t2l R.A BERNER 1984 : Sedimentary pyrite e Gecchimica et Cosmochimica Acta, vol 48, 605-615 fo r matio n : An up dat t3l R.A BERNER, J.T WESTRICH, 1985 : Bioturbation and the early diagenesis of carbon and sulfur Amer J Sci, vol 285,193-206 [4] palri oe R BOURROUINLH, 1994: Environnements et nvironneme nts carbonatd s mari ns' Enregis- treurs et indicateurs de I'evolution de I'environnement en zone tropicale (Ed Maire R., Pomel S', Sa- lomon J N., Presses Universitaires de Bordeaux)' [5] BzuA{ JONES, 1992 : Construction of spar nhu khOng ph6t hi0n thdy tAng tr0n ctia trdm tich dAm ldy bi oxy ho1 manh calcite crystals around spores- Journal of Sedimen- Tuy nhiOn, didu kiOn dc c6c kct tu c6 hinh dang NGLIEN HUU CHIEM, 1993 : Geo' pedological stud,' of the Mekong delra Southeast nh6nh c6c trAm tich duoc nghi€n c(ru r'an li vdn dc tdn tai Kel tua carbonat c6 the dien theo c6c 16 r6n-e trdm tich rfr Asian studies, vol 31, Chttong trinh didu tra co bdn cdp Nhd ntdc 60-02' Tich tu carbonat dang calqit gidu magne phd biOn trdm tich cira mOi trudng bi khrl mqnh tuong doi kh6p kin (ddm ldy man, vfrng vinh) tai chau thd sOng Ciiu tnng Su hinh thdnh c6c tich vd tu ndy dien qu6 trinh bidn chdt so khdi trdm tich : khu sulphat va tich lu! 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