祁连山木里三露天天然气水合物层段碳酸盐矿物学地球化学特征

祁连山木里三露天天然气水合物与碳酸盐相伴产出是一种常见现象。为探讨这些碳酸盐的形成环境，对碳酸盐进行了矿物X射线衍射分析、主微量元素 测试以及碳氧同位素测试。X射线衍射结果表明，样品中碳酸盐矿物主要由方解石、白云石以及少量菱铁矿组成。微量元素和稀土元素特征显示碳酸盐形成于干旱氧化环境。δ¹³C_VPDB为-2.3 ‰~3.77‰，平均为2.43‰；δ18OVPDB为-17.90‰~-10.69‰，变化范围不大，碳氧同位素显示碳酸盐矿物中的碳可能为天然气水合物分解、白云石沉淀和湖水混染等联合作用所致，氧的 来源可能受大气降水影响。

Mineralogical and Geochemical Characteristics of Carbonates Occurred at Gas Hydrate-bearing Intervals in Sanlutian of Muli of Qilian Mountains

It is a common phenomenon that gas hydrate occurs with carbonate in Sanlutian of Muli of Qilian Mountains. In order to discuss the formation environment of carbonate, the X ray diffraction analysis, the main-trace element and the carbon and oxygen isotope test of the carbonates were carried out. X ray diffraction results show that the carbonate minerals in the samples are mainly composed of calcite, dolomite and a small amount of siderite. Trace elements and rare earth elements show that the carbonate minerals are formed in the dry and oxidizing environment. δ¹³C_VPDB is -2.3‰ to 3.77‰，and the average value is 2.43‰；δ18OVPDB is -17.90‰ to -10.69‰，and the variation is small. Carbon and oxygen isotopes show that the carbon in carbonate may be influenced by the combined effects of gas hydrate dissociation, dolomite precipitation and lake water pollution, and the possible sources of oxygen may be influenced by the atmospheric rainfall.