摘要
震旦纪—古生代期间四川盆地发生过兴凯地裂运动及峨眉地裂运动两次强烈的构造热液活动。盆地周缘的金属成矿作用主要发生于晚二叠世,与峨眉山岩浆活动相关,形成了会泽、大梁子、天宝山等一系列MVT型铅锌矿,及会理小石房、汉源黑区-雪区SEDEX型铅锌矿。盆地内部常见热液矿物组合,有:白云石-石英-黄铁矿组合、黄铜矿-黄铁矿-孔雀石组合、天青石-硬石膏-石英及白云石-萤石组合、白云石-天青石等组合;其主要呈溶蚀脉或孔洞状、以及交代状交代白云岩、页岩及生物屑含云灰岩或灰岩等。四川盆地二叠系长兴组礁白云岩与阳新统灰岩中发育的砂糖状白云岩可能均是热液作用产物,或经历过热液蚀变。震旦系87Sr/86Sr比值对比表明在深埋过程中,震旦系具有三期外来侵蚀性富87Sr/86Sr比值的流体充注;震旦系裂缝中白云石,奥陶、志留系裂缝中的方解石的87Sr/86Sr比值明显高于自身围岩与同期海水87Sr/86Sr比值,三者相近的值表明在后期构造隆升过程中超压热液释放,发生跨层流动。热液可影响区域热流值,使川西南地区地温梯度明显高于川东(北)地区,致使二叠系-三叠系及下寒武统具有相对较高的沉积期地温。盆地周缘铅锌矿床与有机质及盆地油田卤水具有密切关系。热液作用为震旦系—古生界储层中与构造相关的溶蚀孔洞缝提供了一种新的溶蚀机理,以及先前多解释成埋藏成因砂糖状白云石、礁白云岩可能均是热液成因;热液白云岩与围岩基质相比具有相对较高储层物性,特别是在区域性低孔隙度低渗透率的震旦系—古生界中形成热液白云岩优质储层,为今后四川盆地震旦系—古生界碳酸盐岩勘探提供了一个重要方向。
There are two stages of tectonic hydrothermal fluid activities forming in Xingkai taphrogeny and Emei taphrogeny in Sichuan basin during the Sinian-Palaeozoic periods. Mineral accumulation around Sichuan basin mainly formed in late Permian, which was related to Emei magmatic activity, and formed a series of MVT Pb-Zn ore bodies,such as Huize, Daliangzi,Tianbaoshan,and formed SEDEX Pb-Zn ore bodies in Xiaoshifang of Huili, Heiqu-Xuequ of Hanyuan. The commonly hydrothermal mineral combinations are dolomite-quartz-pyrite, chalcopyrite-pyritemalachite,celestite-anhydrite-quartz, dolomite-fluorite and dolomite-eelestite. These combinations mainly replace dolomite, shale, bioelastic dolomitic limestone or limestone etc. The genesis of reef dolomite in the Changxing Formation of upper Permian and saccharoidat limestone in the Yangx- ing series may be affected by hydrothermal fluid process,or suffered by hydrothermal alterations. Geochemistry is characterized by poor in strontium or natrium, and rich in ferrum or manganese, depleted in 180 with homogenization temperature of 156 ℃-256 ℃. Hydrothermal fluids can affect provincial heat value, leading to geothermal gradient in the southwest Sichuan province being higher than that in the northeast Sichuan province, and resulting in a situation of relatively high sedimentary geothermal temperature in Permian-Triassic and lower Cambrian periods. Pb-Zn ore bodies occurred around the basin margin, organic and brine in oil field are of close relatiionship. Hydrothermal fluid process provides a new dissolution mechanism for dissolution pores, cavies and dissolution fractures which are related to tectonic activities in the Sinian-Palaeozoic reservoirs. The genetic factor of saccharoidal dolomite and reef dolomite,which were previously interpreted as burial origin, may be resulted from hydrothermal fluid activity. There is much better reservoir physical property in hydrothermal dolomite than that in matrix host rock, especially in provincial low porosity and low permeability rocks which can form high quality reservoir in the Sinian-Palaeozoic.
出处
《矿物岩石》
EI
CAS
CSCD
北大核心
2008年第3期41-50,共10页
Mineralogy and Petrology
基金
国家重点基础研究发展计划“973”项目(2005CB422106)
关键词
震旦系-古生界
热液作用
碳酸盐岩
成藏效应
成矿效应
四川盆地
Sinian System
Palaeozoic
hydrothermal fluid process
carbonate rocks
effectiveness on petroleum accumulation
effectiveness on mineral accumulation
Sichuan Basin
