Discovery of the southwest Dongsha Island mud volcanoes amid the northern margin of the South China
Discovery of the southwest Dongsha Island mud volcanoes amid the northern margin of the South China
复制标题
华南北缘西南东沙岛泥火山的发现
DOI：
10.1016/j.marpetgeo.2017.09.021
复制
发表时间：
2017
影响因子：
4.2
通讯作者：
Liu Xingjian
中科院分区：
文献类型：
--
作者：
Yan Pin;Wang Yanlin;Liu Jun;Zhong Guangjian;Liu Xingjian
东沙盆地环绕着位于南海中国北缘的东沙岛，其特点是新生代沉积薄(~0.5公里)，覆盖在厚(达5公里)的中生代地层上。最近，在东沙岛西南部的斜坡上进行了多次地球物理和地质调查，包括多通道反射地震、海底剖面和海底疏浚，水深从400米到2000米不等。一个新的发现是那里有许多大小不一的海底泥火山，通常高50-200米，宽0.5-5公里。地球物理剖面记录了它们的不同寻常的特征，例如，海底粗暴起伏，高幅度海底，反射率高，在海床以上的水柱中高达50米的雾状双曲绕射，以及海底以下2e3公里或更深的内部反射混乱和消失。泥火山提供了丰富的高度多样性的动物群，如石珊瑚、柳珊瑚、黑珊瑚、管虫、玻璃海绵、苔藓动物等，表明了化学合成群落的蓬勃发展，其中似孔雀石珊瑚的珊瑚和似真海绵的玻璃海绵在南中国海区属首次报道。与之伴生的还有丰富的自生碳酸盐、结核、板片、生、角砾岩和角砾岩，并有生物碎屑集合体。此外，大规模泥石流和同种粗粒石英、长石、电气石并存，很可能是泥火山作用带来的。对底水样品进行的地球化学分析显示，溶解的甲烷浓度比本底平均值高出4倍。这些结果为持续的和历史上的泥火山作用提供了全面的证据。推测逸出的甲烷气主要来自中生代地层。泥火山占地1000平方公里以上的深水斜坡大省，是东沙盆地天然气水合物和天然气的远景。
The Dongsha Basin, circling Dongsha Island that is amid the northern margin of the South China Sea, is.characterized by thin (~0.5 km) Cenozoic sediments veneering on thick (up to 5 km) Mesozoic strata..Recently, several geophysical and geological surveys, including multiple channel reflection seismic, subbottom.profiling and benthic dredging, have been conducted on the slope southwest to the Dongsha.Island, where the water depth varies from 400 m to 2000 m. A novel discovery is numerous submarine.mud volcanoes of various sizes over there, typically 50e200 m high and 0.5e5 km wide. Geophysical.profiles document their unusual features, e.g., roughly undulating seafloor, high-amplitude seabed.reflectivity, foggy hyperbolic diffractions up to 50 m in water column above seabed, and internal.reflection chaos and wipe-out down to 2e3 km level or deeper below the seabed. Benthic dredging from.the mud volcanoes gives abundant faunas of high diversity, e.g., scleractinian (stony coral), gorgonian,.black coral, thiophil tubeworm, glass sponge, bryozoan etc., indicating booming chemosynthetic community,.among which the Lophelia pertusa-like coral and the Euretidae-like glass sponges are the first.reports in the South China Sea. Concomitantly with them, there are also abundant authigenic carbonate.nodules and slabs, raw, brecciated and breccias with bio-clasts congregation. Besides, there coexist.massive mudflows and allogenic coarse-grained quartz, feldspar and tourmaline most likely brought out.by mud volcanism. Geochemical analysis of the bottom water samples give dissolved methane concentration.up to 4 times higher than the background average. These results lend comprehensive evidences.for the ongoing and historical mud volcanism. The escaping methane gas is inferred to source.mainly from the Mesozoic strata. Occupying a large province of the deep water slope, ca. 1000 km2 or.more, the mud volcanoes is prospective for gas hydrate and natural gas for the Dongsha Basin.