二氧化碳气成藏的断裂控制作用

Control Actions of Faults to Form Carbon Dioxide Gas Accumulations

对二氧化碳(CO_2)气成藏来说,各种级别不同性能断裂的存在是必不可少的条件,按其在成藏过程中功能的不同可以分为成气、疏气、储气和封气四种类型。断裂对幔源-岩浆成因CO_2气最重要的作用是对幔源气的运移疏导作用。幔源CO★存在于地下深处,其释放的途径有两种:一是没有岩浆喷发和侵入的情况下,沿深断裂直接释放;二是在岩浆喷溢、侵入过程中冷却时释放的幔源气,断裂作为岩浆喷溢、侵入的通道。岩浆活动为幔源型CO_2成藏提供了主力气源,深大断裂为CO_2提供了运聚的通道和赋存的空间。断裂对变质成因CO_2气的最重要的作用是对CO_2气的生成和疏导作用。在动力变质作用中,断裂活动的构造热使碳酸盐岩分解释放CO_2,压扭性断裂带与张启性断裂的交汇带即成为变质成因CO_2的生成与排放中心;在接触变质作用,断裂不仅作为岩浆或高温热液的通道使得围岩变质释放CO_2,而且也是变质成因CO_2运移释放的通道。

various grade and mechanical property of faults is absolutely necessary to form Accumulations of large volumes of carbon diox ide （CO2）, which can be divided into four kinds： creating, transmitting, gathering and sealing faults by their control action to CO2 gas. The transmitting action of faults is the most important to mantle-magma-derived CO2. There are two kind of mode to release mantle-derived CO2 first, mantle-derived gas is immediately released along deep faults in the condition of no eruption/in- trusion of magmas; second, mantle-derived gas is released with magma cooling during magmas erupt/intrude. Magmas are principal gas source of mantle-derived CO2, while faults supply transmitting passage and gathering space. The creating and transmitting actions of faults are the most important to meta-morphogenic CO2. In dynamic metamorphism, shear heats make carbonatite decompose to release CO2, and the cross field of tensile and compressive faults is creating and releasing focus of meta-morphogenic CO2. In contact metamorphism, faults act as transmitting conduit of magma/hydrotherm and CO2 released during country rock alteration.