冷泉流体沉积碳酸盐岩的地质地球化学特征  

Geology and Geochemistry of Cold Seepage and Venting-related Carbonates

作　　者：陈多福[1] 陈先沛[1] 陈光谦[1] 

机构地区：[1]中国科学院广州地球化学研究所,广州五山510640

出　　处：《沉积学报》2002年第1期34-40,共7页Acta Sedimentologica Sinica

基　　金：国家自然科学基金 (批准号 :40 0 72 0 4 4 );科技部基础司的专项资助

摘　　要：冷泉流体是指来自海底沉积界面之下的低温流体以喷涌和渗漏方式注入盆地 ,并产生系列的物理和化学及生物作用 ,这种作用及产物称为冷泉。它是继洋中脊以盆下源中高温流体的热泉被发现和研究之后的又一个新的盆地流体沉积领域。日前研究较多的是以水、碳氢化合物 (天然气和石油 )、硫化氢、细粒沉积物为主要成分 ,温度与海水相近的流体 ,广泛发育于活动和被动大陆边缘斜坡海底。冷泉流体沉积体系发育高密度的化学自养生物群 ,以碳酸盐岩和天然气水合物为主 ,有少量的硫化物和硫酸盐等。冷泉碳酸盐岩的产状有丘、结核、硬底、烟囱、胶结物和小脉等 ,以化学自养生物碎屑和多期次的自生碳酸盐胶结物组成的生物丘最为常见 ,它在物质来源、形成环境、形成作用等方面与传统来源于海水碳的碳酸盐岩建隆不同 ,用术语Chermoherm表示 ,以区别于传统海水碳酸盐岩建隆术语bioherms、lithoherms、pseudobioherms和biostromes。地层中石化的化学自养生物丘常是含有大量底栖生物化石的碳酸盐岩建隆产于深水相沉积地层中 ,在沉积环境和相分析上出现纵向和横向的不连续 ,甚至出现反常现象。矿物以镁方解石、白云石和文石为主 ,与传统的碳酸盐岩相似 ,在地球化学组成上最大的区别是冷泉流体沉积碳酸盐岩的碳来源于冷泉体系?Cold seepage and venting is a fluid seepage and venting mainly composed of water, hydrocarbon(gas and crude oil), hydrogen sulfide and fine sediments derived below seafloor. Its temperature is similar to sea water and widely occurs on the seafloor of continental slope of active and passive margins. Cold seepage and venting-related chemosynthetic communities are highly in organism density, mainly mussels, clams, tube worms and bacterial mats. The sediments in cold seepage and venting are mostly maed up of carbonates and gas hydrates with minor sulfides and sulphates. The chemosynthetic carbonates occurred as buildup, chimney, cement, nodule, hardgroud and fine vein, and generally as buildup of chemosythetic bioclasts and multi-stage authigenic cements. The carbonate source, sedimentary environment and sedimentations are different with normal carbonates,of which carbon is from sea water. Therefore, using term 'Chermoherm' represents the chemosynthetic carbonate buildup to distinguish from the terms of bioherms, lithoherms, pseudobioherms, biostromes of carbonate buildups in normal sea environment,in which the carbon is from sea water. In strata, Chermoherm frequently occurred in abyssal sediment strata as a carbonate buildup containing a lot of fossils of benthic fauna. There are disrupted sedimentary phase and environments in longitudinal and cross strata section, so much as turnover. Carbonate minerals in chemosynthetic carbonates are primarily Mg-calcite, aragonite, and dolomite,which are not different with normal carbonates. Carbon isotope values in chemosynthetic carbonates are very low due to bacteria mediation. Cold seepage and venting occurred along fault zone or permeable beds and at the surface expression of mud volcano and salt diapirism. Cold seepage and venting fluids are derived from formation fluids driven by a combination of (1)pore-space reduction of rapid sedimentation and tectonic compaction, deformation and cementation, and (2)increased buoyancy due to a decrease in pore-fluid density re

关 键 词：冷泉流体沉积 化学自养生物碳酸盐岩 生物丘 地球化学特征 胶结作用 充填作用 沉积环境 深水相沉积 

分 类 号：P588.245[天文地球—岩石学] P59[天文地球—地质学]