特提斯构造域海底流体逃逸活动特征及其控制因素

Characteristics and controlling factors of submarine fluid escape in Tethys tectonic domain

海底流体逃逸活动会显著地改变海底地形地貌,产生麻坑、泥火山等地貌和冷泉羽状流现象。特提斯构造域是世界上油气最集中的构造域,流体逃逸活动广泛发育,形成的复杂流体逸出结构,对海洋油气勘探、全球气候变化研究等方面具有较好指示作用。本文选取特提斯构造域主要海域,系统总结其海底流体逃逸活动特征,发现特提斯构造域海底流体逃逸活动多分布在被动大陆边缘和弧后裂谷盆地等地质背景中,其中地中海、黑海和南海广泛发育海底冷泉、麻坑和泥火山等流体逃逸特征,而波斯湾和澳大利亚西北部近海大量发育碳酸盐岩。海底流体逃逸活动主要受控于活动断裂、沉积物超压、地震活动、海平面变化、潮汐活动和海底滑坡等海洋与地质因素。在不同海域,流体来源也不尽相同(热成因、生物成因以及天然气水合物分解),大多数通过断层、泥火山和气烟囱等通道运移。建议重视对特提斯构造域海底流体逃逸活动发育区的调查和探测,深入分析与之相关的海底流体逃逸地貌发育机制,以及其特殊海域背景下的海洋与地质因素控制作用,总结建立其海底流体逃逸活动模式及相关理论。

Seabed fluid escape may significantly change the seafloor topography,resulting in some geomorphic features such as pockmarks,mud volcanoes and cold seep plumes.The Tethys tectonic domain,the most hydrocarbon-rich domain in the world,hosts substantial fluid escape-related structures that can act as good indicators for offshore hydrocarbon exploration and global climate changes.Based on previous researches of major sea areas in the Tethys tectonic domain,this paper systematically summarized the characteristics of the seabed fluid flow,which shows that the seabed fluid escape activities of the Tethys tectonic area are mostly distributed in passive continental margins and back-arc rift basins.Seafloor manifestations of fluid escape including submarine cold seeps,pockmarks and mud volcanoes,are widely distributed in the Mediterranean Sea,the Black Sea and the South China Sea,however,massive carbonate-related structures are the prominent seabed fluid escape features in the Persian Gulf and the northwestern shelf of Australia.Seabed fluid flow is a dynamic process in the Tethys tectonic domain.The main marine and geological factors controlling fluid escape include active faults,sediment overpressure,seismic activities,sea-level changes,tidal activities and seabed landslides.Fluids are sourced from different intervals(thermal,biogenesis,and natural gas hydrate decomposition)in different sea areas,and the migration of fluids is mostly through fault planes,mud volcanoes and gas chimneys to the seafloor.To summarize and establish the model and theory of seabed fluid escape,it is suggested that more attention should be paid to the investigation and detection of the development areas of the seabed fluid escape activities in the Tethys tectonic domain.Moreover,the further analysis of the mechanism of the fluid escape-related geomorphic features,as well as the marine and geological controls in the special oceanic regions will provide basic support for the subsequent research.