Tap cU Khoa hoc va Cong nghe Bien; Tap 14, So 4; 2014: 341-347 DOI: 10.15625/1859-3097/14/4/5820 http://www.vjs.ac.vn/index.php/jmst
VAl NET TONG QUAN VE NUI LlTA BUN TREN THEM LUC BIA
Tr4n Tuan Dung*', Phi Tririmg Thanh', DoSn Thi Hung^
'Vi$n Dia chat va Dia vat ly bien-Vien Han lam Khoa hpc va Cdng nghd Vift Nam
^Vidn Han lam Khoa hpc va Cdng nghd Viet Nam 'E-mail: [email protected]
Ngay nhaln bai; 23-5-2014
TOM TAT: Nui lira biin xdy ra chu yiu irong phgm vi cdc be trdm tich, tren ddt hen vd cd du&i day biin, tgi nhihig khu vuc xung yeu hogc nai gigo cdt giiea cdc he thong dut gay hoat dong kien tgo ben trong vd Trdi ddt gdy ra. Hogt dgng cUa chiing du&i bien co the gdy ra rdi ro tiem ndng ddi v&i cdc hogt dpng khoan dau khi ciing nhu v&i du&ng ong ddn ddu-khi. Qua thai gian, cdc hogt dgng tim kiim, tham dd va khai thac ddu khi tren khu vuc Bien Dong diin ra khd soi dgng, dgc biit Id & khu vuc cdc bi trdm lich trin thim luc dia Vi vgy, trong bdi bdo ndy. cdc tdc gid tap trung vdo phdn tich khdi qudt mot si dgc diim cua nui lira biin ciing nhu Id ca che hinh ihdnh vd mdi quan he cua chung v&i khi hydrate, truot la ngdm, ldm tiin di dinh hu&ng cho nhung nghien cieu sau ndy.
Tie khoa: Nui lua bun. Iruat la ngdm, khi hydrate.
M d D A U
Nghien ciiu mii lua bun dugc quan tam nhidu tir cac nha khoa hgc frong nhtmg thap ky gin day bdi su nil ro tiem nang eiia nd ddi vdi cac hoat dpng khoan diu khi, thidt lap dudng dng din frdn bd mat day bien, ciing nhu d nhimg khu vuc cd tidm nang khi hydrate cao.
Niii lua bim dugc hinh thanh tucmg tu nhu niii lua magma. Chiing thudng xay ra tai nhiing khu vuc xung ydu hoac noi giao cat giiia cac he thdng diit gay do hoat dong kien tao ben frong vd frai gay ra. Tuy nhidn, su khac bidt giiia niii lua bun va mii liia magma la: Niii Iiia magma dugc thanh tao d dudi sau, nai ranh gidi giira cac mang thach quydn, con niii lira bun dugc hinh thanh d ndng ban, frong pham vi cae bd frim tich. Nui Ifra bun thudng xuit hipn d do sau tii 8 km ddn 22 km.Hoat ddng ciia mii Ilia biin thudng lien quan ddn su xuit hien ciia khi mdtan, khi carbonic va nito. Theo mpt sd nghidn euu, khi mii lira bim hoat dgng, Iugng khi mdtan dugc giai phdng chiem khoang 70 - 99% Iugng klii thoat ra. Ngoai ra, cac ket qua nghidn cuu khac cho thiy, nhi?t do ndng chay
cua dung nham niii lua magma phim frao dat tir 700"C ddn 1.200"C, frong khi dd quanh khu vuc mieng mil lua bun nhiet do lai rat thap, cd thd dat den nhiet dp ddng bang. Niii liia bim la kdt qua cua mgt cau tnic xuyen thiing, dugc tao ra bdi ap luc biin, khi tham nhap tir ben dudi ldp vd Trai Ddt. Hien nay, khoang 2.000 mii Ilia biin da dugc phat hien fren toan thd gidi.
Viec tham dd cac viing bidn sau van dang dugc tidp tuc, con sd nay du kien se tang dang ke.
Mgt sd nghidn ciiu khac cung da udc tinh ring tdng sd mii lira bim dudi day bidn cd the tir 7.000 ddn 1.000.000. Ngpn mii lira bim Idn nhit fren the gidi cd dudng kinh den 10 km va eao gin 700 m. Niii lira biin Kazakov cd dudng kinh 2,5 km va cao 120 m (Krastel, 2003) [1].
Theo udc tinh cua Milkov (2000) [2], sd lugng niii liia bim dudi day bidn cd the dat tir 10^ d6n 10^ (hinh 1). Nui lua biin xay ra chu ydu frong pham vi cac be frim tich, trdn dat lien va ca dudi day bidn, dpc theo cac diit gay va cd ngudn tuang tu nhau (Holland, 2003) [3].
Nghidn ciiu ciia J. Chow (2001) [4] chi ra su cd mat ciia dtit gay xung quanh mii lira bun. Niii
Tran Tudn Ddng, Phi Trudng Thdnh, ...
lua biin cung cip nhiing thdng tin huu ich ve thanh phin thach hoc va chat long d dudi sau.
Mac dii nghien ciiu vd mil lua biin da dugc dang tai kha nhidu fren cae tap chi Qudc tl, song nhung thdng tin vd nd vSn it dugc de cap frong mpt sd van lieu frong nudc. Vi vay frong ndi
dung bai vidt nay, cae tac gia cung cap them mpt sd thdng tin nfra vd mii liia biin de ngudi dpc co thd nhm bao quat hem thay yi chi cd mot loai niii lua phun trao magma. Cd the ndi, bai viet mdi chi mang tinh phan tich tdng hgp ve mgt sd nghien eiiu vd cac hoat ddng cua nui liia bim, xay ra free bd mat day bidn.
Hinh 1. Ban dd vi fri phan bd mii liia biin (1) va khi hydrate (2) (Milkov, 2000) [2]
Mdt sd nghidn cthi da chi ra rang, khi hydrat nim ben dudi sudn ddc cd the la nhan td ddng gdp kich hoat cho cac vu trugt Id ngam.
Khi hydrat gidng nhu la bang, bao gdm nudc va khi ddt tu nhien, dugc dn djnh tai cac dieu kien nhiet do va ap suat binh thudng dudi day bidn. Khi nhiet dp tang hoac ap luc giam, khi hydrat trd nen khdng dn dinh, lam cho hydrat tan chay va thoat khi dudi dang bong bdng. Dp tan chay va thoat khi den mdt mirc dp nao do thi se pha va dp bdn viing cua sudn doe, gay nen hien tugng trupt Id ngam [5, 6].
M O T SO NGUYEN NHAN VA CO CHE THANH TAG NIII LU'A BUN
NhO'ng nguyen nhan va ca chfi dan ddn hinh thanh niii lira bun dudi day bidn da dugc
nghidn ciiu bdi Hedberg (1974) [7], Barber va nnk (1986) [8] ... Cac cau hdi, tai sao va mii lira biin hinh thanh nhu thd nao se dugc giai dap theo 4 nhdm ly do sau.
Ly do dia chat:
Tram tich phu cd be day 8 - 2 2 km, chu yen la fram tich luc nguydn;
Su cd mat ciia cac Idp set deo d be mat dudi;
Su dao ngugc mat dp da;
Su xuat hidn ciia khi tich tu d dudi bd mat dudi sau;
Ap suat hinh thanh cao bit thudng.
Ly do kidn tao:
Sut liin nhanh cua trim tich phii do tdc dp tich tu fram tich cao;
Su xuat hien ciia diapir hoac nhfrng ndp udn ldi;
Su xuat hidn eiia diirt gay;
Nen ep kien tao;
Hoat ddng dia chan;
Cac qua trinh dang tinh.
Ly do dia hda:
Cac the he dau khi ben d be mat dudi sau;
Tinh trang mat nude cua cac khoang vat set.
Ly do dia chat thiiy van:
Ddng chat luu chay dpc theo cac ddi diit gay-
Co chd thanh tao mii lira bim dugc nghien cuu bdi Brown and West brook (1,988) [9], Hjelstuen va nnk (1999) [10], va nhieu nghien cihi khac da cho thay niii lira biin hinh thanh theo 2 ca chd:
Co che thu nhit la su hinh thanh ciia mii lua bim true tiep trdn be mat day bien bdi su xuydn thirng eiia cac diapfr set va ddng chat luu di chuydn dpc theo than diapir.
Co chd thir 2 la su hinh thanh niii lira bim, ket qua cua su gia tang bun hda ldng dpc theo nhung diit gay va khe niit.
DAC TRU>(G CUA NUI LU'A BUN VA N H O I G D A U H I E U NHAN D4.NG
Vdi net tdng quan ve mii lua bim ...
Nui lira biin cd nhiing dac tnmg ciia da fram tich, dugc tao ra tai ncri hdn hgp fram tich hat min giau chat Idng, thudng dugc ket hgp vdi nhiing manh vgn da hoac biin ran chic, dugc thoat ra trdn be mat day bidn (Hovland et al., 1988; Barber et al, 1986; Cita et al., 1981;
Staffiniet al., 1993) [3, 8, 11, 12]. Diu hidu nui lira bim duge nhan ra dua vao nhiJng dau hieu dia vat ly ridng bidt (Brown and Westbrook, 1988; Fusiand Kenyon, 1996; Henry et al., 1990; Vogt et al., 1991, 1999) [9, 13, 14, 15].
Chiing dugc dac trung bdi nhirng dii lieu am hpc (hinh anh multibeam va side scan sonar), sir tan xa ngugc cao tir be mat day bidn gd ghe va tu su tan xa ngugc ciia nhung manh vun bim da. Su tan xa ngugc eao chi ra su cd mat cua ddng biin vdi nhiing manh vun biin nhd len hoac ben trong gin bd mat. Miic dp tan xa suy giam dan theo su gia tang dp day cua lang dgng bim cii phu fren. Milkov (2000) [2] da dua ra hai tieu chuan de nhan dang chinh xac hon vd niii lira biin:
Su ed mat eiia fram tich biin niii liia frong mau Idi bao gdm nhung manh vun biin, ehiia dung nhiing fram tich khac nhau vd tudi, cau tnic va thanh phan ...
Su cd mat cua nhiing dac diem dia hinh dia phuong duge phan bidt bdi mpt dia hinh dac biet va su tan xa ngugc manh (mieng mil lua, ddng biin ...), xae dinh hi nhiing hinh anh side scan sonar, tii quan sat true tiep, quay phim va ehup anh dudi nudc.
Hinh 2. Mat cit dia chan phan xa GeoB 02-003 qua mii lua bun Kazakov, dudng kinh 2,5 km, cao 120 m (Krastel, 2003) [1]
Trdn Tudn Ddng, Phi Truang Thdnh, ...
tl
"£
E
" ''PPP'"'
- - * ' • • • • ' " ^ f ^ ^
Hinh 3. Ban dd dd sau va hmh anh Side scan sonar vd mii lua bim Tuzlukush (Zitter T. A. C. et al., 2005) [17]
Ben canh dd, P. Yin (2003) [16] ciing eho rang nhiing hinh anh am hoc cua niii lira biin dugc dac trung bdi nhung mang xam tan xa ngugc cao tren be mat day bien, dugc phan biet tir nhixng tram tich xung quanh cd mirc dp tan xa ngupc thap hon. Niii liia biin thudng xuat hidn theo cac cum hoac timg nhdm nhd (-Milkov, 2000) [2].
Niii Ifra biin hoat ddng kha da dang, khac bidt ve quy md, didn phan bd va tudi. Tren cac bSng dia chan, nd thudng Iam bidn dang cac da xung quanh mdt each rd ret. Niii lira biin cd the trdi hoac khdng frdi fren bd mat day bidn. Cac dau hidu nay dugc nhan thay rat rd tren mpt sd m3t cat dia ehan phan xa d hinh dudi day (hinh 2, 3).
Cac phuong phap sir dung cho thu thap va phan tich du lieu mil lua biin ehu ydu gdm 2 nhdm chmh, dd la: Nhdm cac phuang phap do
dia vSt ly va side scan sonar, multibeam va nhdm cac phuang phap dia hda. Trong do, nhdm cac phuang phap dia vat ly dua ra nhimg thdng tin chi Udt vd dp sau, hinh dang, kich thudc va didn phan bd eua chiing ... Tuy nhien, dd nh§n dang chinh xac nui lua bun cin phai co su tham gia ciia nhdm cac phuang phap dia hda, bao gdm vide lay mau va xac dinh eac thanh phan vat chat frong do. Ndu chi sir dung phuong phap rieng le eho timg nghien ciiu thi viec dua ra kdt qua se cd nhiing sai sdt. Chang han, hinh 4 va hinh 5 bidu didn hoat ddng cua niii lua phun trao magma va boat ddng cua niii lua biin tren bang dia chin. Trong i)ham vi niii lua hoat ddng, trudng sdng dia chin thd hien kha ddng nhat va ro rang. Vi vay, vide phan biet gitra mii lua bim va nui_ lua magma la ciing khdng de, viec dua ra quydt dinh ddi hdi phai cd su kdt hgp ciia cac phuang phap phan tich dia chat va dia vat ly khac.
Hinh 4. Mat cit dia chin ndng phan giai cao tuydn 09050403 qua mieng mii lira phun trao magma khu vuc thdm luc dia Vung Tau - Binh Thuan
Vdi net tdng quan ve nui lua biin .
5000 5100 5200 5300
Hinh 5. Tuyen dia chin TASIO 8 cit qua khdi nhd diapfr Guadalquivir [18]
QUAN H ? G I C A NUI LU'A BUN, KHI
HYDRATE VA TRU*OT L O NGAM Nghien cuu vd quan he gifra khi hydrate va niii lira biin da dugc quan tam bdi nhidu nha khoa hpc, Ginsburg et al., (1999), Eldholm, O., et al., 1999) [19, 20] ... Cdc edng trinh nghidn Cliu frdn cho rang khi hydrate cd nhieu dac didm lien quan ddn mii lira bun. Khi hydrate dugc hinh thanh va tda ra tu phin tnmg tam ciia mii liia bim. Ham Iugng khi hydrate frong frong fram tich thay ddi tu 1 - 2% den 35% ve thd tich va thay ddi thong qua khu vuc mii lira biin Cling nhu theo do sau. Mdtan la thanh phan ehinh ciia khi hydrate. Milkov (2000) [2] da udc tinh ring Iugng metan dugc tich ty frong khi hydrate lidn quan ddn niii lira bun fren toan thd gidi vao khoang lO'"- 10'^m^
Cd the ndi, bidn ddi khi hau ciing la mgt van de nghidm frong, gdp phan thiic day cac qud frinh trugt Id ngam. Syr gia tang nhiet dp d day, su ndng ldn ciia cac vung nudc sau dugc cho la mdt frong nhiing nguyen nhan gay nen su thoat Ichi mdtan, qua trinh do gdp phan vao su sup do ciia cac sudn luc dia ngam (Kennefr etal.',2003)[21].
K E T L U ^
Niii Ilia bim dugc thanh tao d dp sSu nhd, thudng frong pham vi cac be fram tich. Nhiet do ciia mii nua bim rat thap, cd the dat den nhiet dp dong bang. Khi niii lua biin boat dpng chiing thudng giai phdng ra mgt lugng khi ma chii ydu la khi mdtan. Trdn bang dia chan,
nhiing dau hieu ciia mii lua bim va nui Ifra magma la kha gidng nhau, vi vay de xac dinh chinh xac loai niii liia thi can phai cd su kdt hgp giiia cac phuang phap dia chat va dia vat Iy.
Hoat ddng cua mii lua bun dudi day bien cd the gay anh hudng den boat dpng khoan, lip dat dudng dng dan dau, khi ... Bdn canh dd, hoat dpng ciia niii Ifra biin cdn cd the eung cap nhfrng dau hidu ve su tdn tai hii khi d cac can tnic dudi sau.
Nhidu noi frdn them luc dia Viet Nam cd gradient dia hinh day bien bien ddi manh. Cac ldp fram tich d day cd dp day rat ldn va bi phan cat manh me bdi cac he thdng diit gay. 6 dd Cling tdn tai nhidu cau tnic mii lua, dd la ngudn gde tiem an ciia nhfrng vu trugt Id ngim. Can phai cd nhiing nghien ciiu chi tidt vd mdi lien quan gifta xuat hien mii lua biin cung nhu la vai trd ciia bien ddi khi hau toan cau den trugt Id va tin suit xuit hidn trugt ngam.
Ldi cSm on: Cac tac gia cam an Dd tai KC09.il/ll-15 da hd frg cac dieu kidn cin thidt dd hoan thanh nghien cuu nay.
TAI LIEU THAM KHAO
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Trdn Tudn Ddng, Phi Trudng Thdnh, ...
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1993. Mud diapfrs of the Mediterranean Ridge: sedimentological and micropaleontological study of the mud breccia. Rivista italiana di paleontologia e sfratigrafia, 99(2): 225-254.
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Distribution of mud diapirism and other geological stiiietures from long-range sidesean sonar (GLORIA) data, in the Eastern Mediterranean Sea. Marine geology, 132(1): 21-38.
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5 7 - 6 7 .
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Vdi net tdng quan vi nui lira biin ...
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2 1 . Kennett. J. P., Cannariato, K. G. Hendy. I.
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OVERVIEW OF SUBMARINE MUD VOLCANO
T r a n T u a n D u n g ' , Phi T r u o n g T h a n h \ D o a n T h e Hung^
'institute of M a r i n e G e o l o g y a n d G e o p h y s i c s - V A S T V i e t n a m A c a d e m y of Science and T e c h n o l o g y
ABSTRACT: Mud volcanoes occur mostly within the sedimentary basins, both qr^-.land and seabed, where are weak areas of Earth crust or intersection of the fault systems. The activities of submarine mud volcano might cause potential risks for drilling operations and setting oil and gas pipeline on the sea floor. The activities of exploration and exploitation of oil and gas in the East Sea are pretty strong, especially in the sedimentary basins of the continental shelf Therefore, m this paper, Ihe authors focus on essential analysis of some characteristics of mud volcanoes as well as the mechanism of formation and their relationships with gas hydrate, submarine landslide as a premise for the next researches.
Keywords: Mud volcano, submarine landslide, gas hydrgte.
