海底黑烟囱的识别研究及其科学意义

THE IDENTIFICATION OF THE FOSSIL BLACK SMOKER CHIMNEY AND ITS IMPLICATION FOR SCIENTIFIC RESEARCH

现代海底黑烟囱广泛出现于大洋中脊、弧后盆地、浅海及大陆裂谷等环境,形成巨大规模的块状硫化物,并且在黑烟囱周围发现了化学自养细菌。海底硫化物黑烟囱具有明显的柱状—锥状构造形态,常保留通道构造,矿物同心圈状分带明显。黑烟囱的形成涉及热液流体与海水相互作用,外壁快速沉淀及通道内部硫化物结晶等过程。深部岩浆热源、热液沿裂隙集中流动和持续喷发,有利于形成大规模黑烟囱构造。海底硫化物丘体的钻探及其与地史时期块状硫化物的对比研究表明,它们具有相似的内部构造和矿床分带特征。黑烟囱的生长、垮塌以及丘体内部角砾化、交代、重结晶作用,有助于大规模矿床的形成。最后,在块状硫化物中寻找黑烟囱残片的研究,对于探讨成矿过程与早期生命活动具有重要意义。

The present day black smoker chimneys and mounds have been widely found in the settings of mid-oceanic ridge, backarc basin, shallow sea and continental rift, which result in the formation of massive sulfide deposits at the vent sites. Moreover, these deep vents support chemosynthetic metabolizing bacteria. The modern sulfide chimneys commonly show evident columnar to conical geometry, characterized with the concentric mineralogical zonation around a central conduit. The black smoker chimney is formed when the mineral laden hydrothermal fluid is mixed with the surrounding ocean water. It begins to grow by the instant precipitation around outer wall, followed by the crystallization of polymetal sulphide on inner wall of conduits. The deeply seated magma as heat source, hydrothermal fluid concentrated within fissures and continuous eruption are favorable to the creation of a giant black smoker chimney. The drilling in sulphide mounds at the ocean bottom and their comparison with VMS (volcanogenic massive sulfide) indicate that they have similar internal structures and mineral zonation. The sulphide mounds of economic value are built with the accumulation of collapsed chimney and breccias, reworked by replacement and recrystalization. Finally, the identification of chimney structures within VMS is very important for the understanding of the process of minerallization and the origin of life.