THE RELATIONSHIP BETWEEN AUTHIGENIC CARBONATE AND GAS HYDRATES IN MAKRAN ACCRETIONARY WEDGE: ON THE BASIS OF M74/3 CRUISE REPORT OF " R/V METEOR" IN 2007
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摘要:
为了探讨马克兰增生楔自生碳酸盐岩与水合物的关系，对2007年流星号的M74/3航次资料进行了总结。结果显示，自生碳酸盐岩与水合物并非一一对应的关系。对于甲烷通量很大的海区，海底和浅表层沉积物中通常没有自生碳酸盐岩，但是可以存在水合物。对于甲烷通量较高的海区，如果海底或浅表层沉积物中存在少量且小块的自生碳酸盐岩，通常沉积物中存在水合物；如果海底或浅表层沉积物中存在大量且大块的自生碳酸盐岩，通常浅表层沉积物中没有水合物，但就目前的资料，尚不能确定其深部是否存在水合物。对于甲烷通量很弱的海区，沉积地层表现为纹层状结构，通常既没有自生碳酸盐岩，也没有水合物。
Abstract:In order to reveal the relationship between authigenic carbonate and gas hydrate in the Makran accretionary wedge, we hereby summarized all the data from the M74/3 cruise of "R/V Meteor" in 2007. The data shows that authigenic carbonate rock has no strict corresponding relationship with gas hydrate. In the sea area where methane flux was very high (such as the No. 5 plume site where water is 2 900 m deep, plume 1 800 m high, with gas hydrates of tubular structure), authigenic carbonate usually does not occur on the seabed or shallow sediments where gas hydrate usually exists. However, in the sea area where methane flux is high (such as, at the No. 2 plume site where water is 1 100 m deep, plume 170 m high, with gas hydrates of vesicular structure), and if there is a small amount of authigenic carbonate on the seabed or in the shallow sediments, then hydrate usually occurs; if there is great amount of authigenetic carbonate on seabed or in shallow sediments, then there is usually no hydrate occurred. Based on the current data, it is uncertain whether there is hydrate in deep sediments. In the sea area where methane flux is very low (such as at MUC-4site, there are no plumes), sediments show clear lamination, there is neither authigenic carbonate nor hydrate.
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Key words:
- methane flux /
- authigenic carbonate /
- hydrate /
- Makran accretionary wedge
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表 1 流星号M74/3航次重力取心站位的碳酸盐岩与水合物(据文献[2]修改)
Table 1. Carbonate and gas hydrate found in gravity cores in the Meteor cruise of M74/3 (modified from reference [2])
GC
No.地区 纬度/N 经度/E 水深/m
样品长度/cm碳酸盐岩/硫酸盐 水合物 GC-1 初生脊5号站位 24°11.749′ 62°44.309′ 2 860
434没有/没有 板状、不规则状水合物 GC-14 24°11.747′ 62°44.428′ 2 860
256没有/有 没有 GC-23 24°11.746′ 62°44.308′ 2 861
360没有/下部没有 底部管状水合物 总结 5号羽状流站位水深2 900 m，沉积物中没有碳酸盐岩结核，所以，水合物的存在与碳酸盐岩无关。但是，如果沉积物中存在硫化物，那么水合物存在的可能性较小。 GC-8 2号羽状流站位 24°50.795′ 63°01.422′ 1 021
30块状碳酸盐岩 没有水合物 GC-11 24°50.789′ 63°01.422′ 1 020
218碳酸盐岩结核 气泡状水合物 GC-25 24°50.799′ 63°01.420′ 1 018
40少量碳酸盐岩结核 厘米级水合物 总结 2号羽状流站位水深1 000 m。如果沉积物中存在大块碳酸盐岩，水合物存在的几率较低。如果沉积物中存在小块碳酸盐岩结核，沉积物中水合物存在的几率较大。 MUC-2 背景站位 24°52.322′ 62°59.859′ 962
35无/硫酸盐 没有水合物 MUC-4 24°52.394′ 62°59.839′ 957
37无/硫酸盐 没有水合物 总结 纹层状地层中既无碳酸盐岩，也没有水合物，是否说明该区缺少上升的气流？ 
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