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冷泉广泛发育于大陆边缘海底,与天然气水合物资源,甲烷温室气体及极端环境的生物资源等重大问题密切相关,因此受到越来越多的关注.目前,已在全球泥盆纪到第四纪地层中发现了代表古代冷泉活动的自生碳酸盐岩或生物化石,但鲜有在我国大陆范围内发现确切古冷泉沉积的相关报道.本文报道了我国大陆境内首个确切的古代冷泉碳酸盐岩沉积——西藏日喀则晚白垩世冷泉碳酸盐岩.日喀则冷泉碳酸盐岩呈结核状产出于晚白垩世日喀则弧前盆地深水浊流沉积地层中,主要由自生碳酸盐矿物(平均约56.2%)、石英和长石碎屑矿物(平均约27.3%)及绿泥石、伊利石和蒙脱石黏土矿物(平均约16.5%)组成.碳酸盐岩结核发育有泥微晶凝块、团块和草莓状黄铁矿等现代冷泉碳酸盐岩中常见的沉积组构.碳酸盐矿物13C值为27.7‰～4.0‰(V-PDB),表明冷泉渗漏的热解成因甲烷是日喀则碳酸盐岩结核的主要碳源.冷泉碳酸盐岩的Ce/Ce*值经La异常校正后显示无真Ce异常,反映形成于以还原为主的环境.日喀则碳酸盐岩结核的这些特征是日喀则弧前盆地海底在晚白垩世发育有冷泉甲烷渗漏活动的有力证据.
Cold springs are widely developed in the seabed of the continental margin and are closely related to such major issues as natural gas hydrate resources, methane greenhouse gases and biological resources in extreme environments, and are therefore receiving more and more attention. At present, In the strata, there are some authigenic carbonate rocks or biotic fossils representing the activities of ancient cold springs, but few reports on the discovery of the exact ancient cold spring deposits in the Chinese mainland.This paper reports the first exact ancient cold spring carbonate Rock Sediment - Late Cretaceous Cold Spring Carbonate in Shigatse, Tibet The Shixihang Cold Spring Carbonate is nodular in the Late Cretaceous Xigaze forearc basin in the deep-water turbidite sedimentary formations and consists mainly of spontaneous carbonate minerals (on average About 56.2%), quartz and feldspar detrital minerals (about 27.3% on average), and chlorite, illite and montmorillonite clay minerals (about 16.5% on average) , Clumps and strawberry-shaped pyrite, etc. The 13C values of carbonate minerals range from 27.7 ‰ to 4.0 ‰ (V-PDB), indicating that the pyrolysis of cold springs is caused by methane Shigatse The main carbon source of acid rock nodules.The Ce / Ce * values of the cold spring carbonate rocks after La anomaly correction show no true Ce anomalies, which reflect the formation of these features in a reduction-dominant environment. These characteristics of Shigatse carbonate nodules It is a strong evidence that the seabed of the Xigaze Pre-arc Basin developed cold spring methane leakage during the Late Cretaceous.