摘要
白云岩不仅常与油气藏共生,更与膏盐或金属矿床关系十分密切,而白云岩的形成至今仍具争议,焦点为白云石化作用过程中 Mg^(2+)的来源问题。白云石化作用常与盆地的深部活动密切相关,一般受深部热液活动控制;在白云石化作用较发育的盆地,其深部普遍存在一个中地壳低速—高导层。据流体包裹体均一温度资料,发现白云岩形成的环境温度高于方解石,且通常远高于正常的地层温度。综合研究认为,盆地深部的中地壳低速—高导层是蛇纹石化橄榄岩,在蛇纹石化过程中释放大量的 Mg^(2+),含 Mg^(2+)热液上升到盆地碳酸盐岩中与 CaCO_3发生强烈的镁交代,形成白云岩;热液中因有卤素 F、Cl、Br 及碱金属 K、Na、Li 等而有盐类沉淀,热液中还含 CO、CO_2、H_2等,它们在蛇纹石化的橄榄岩中可以发生费—托合成反应,合成烃类;蛇纹石化过程中释放的 Ni、Cr、Co、V 等铁族金属是良好的催化剂。
The formation mechanism of dolomitization is a complex,dif- ficult,controversial issue.A discussion on the origin of dolim- itization is presented based on the homogeneous temperature of the fluid inclusions in dolomite and calcite.The homogenous temperatures of fluid inclusions in dolomites in most basins in china are much higher than usual temperatures based the bur- ied depth history,which has shown that dolomite formed in much higher temperatures.The formation of dolomite may be related with the deeper hydrothermal fluids in the basin.It is shown that there is a low-velocity/high-conductive layer in the deep mid-crust in the Tarim,Ordos,Sichuan basins and other petroliferous basins.The low-velocity/high-conductive layer is the serpentinized olivine.During the serpenfinization,the oh- vine can release much Mg^(2+).When the Mg^(2+)-bering hydrother- real fluids rose up into the carbonate rocks in the basins,inten- sive Mg^(2+) alteration took place and dolomite formed.There are much F^-,Cl^-,Br^- and alkaline elements (K^+,Na^+,Li^+ ) in the mantle fluids so that the salt can be deposited.Since there are many types of gases (CO,CO_2,H_2,etc.) in the mantle fluids,the mantle-derived gases can synthesize into hydrocar- bons in the mid-crust (the serpentinized olivine).This new model can explain the following topics:the Mg^(2+) source during dolomitization;dolomite coexisting with gypsum and salt;hy- drocarbon coexisting with dolomite,gypsum and salt.
出处
《海相油气地质》
2003年第1期109-115,共7页
Marine Origin Petroleum Geology
关键词
刍云岩
白云石化
岩石成因
液体包裹体
低速-高导层
热液作用
Origin of hydrocarbon
Origin of rock
Dolomite rock
Dolomitization
Fluid inclusions
Homogenous temperature
Mantle fluids
