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在祁连山冻土区含天然气水合物或存在水合物异常的钻孔岩芯中发育一种半充填或者全充填岩石裂隙的自生黄铁矿,即“裂隙型”黄铁矿,其产状与在该地区发现的水合物产状具有一定的相似性,并且其分布主要集中于水合物层或异常层的下方区域.通过对祁连山冻土区天然气水合物钻探试验井DK-6孔含“裂隙型”黄铁矿岩芯样品开展黄铁矿形态学、微量、稀土元素和硫同位素组成研究发现,“裂隙型”黄铁矿具有沿岩石裂隙面呈台阶状定向排列的立方体形态黄铁矿为主并伴生“圆形”构造、较低的Co/Ni和Sr/Ba值、较低的ΣREE含量、LREE较HREE相对富集和明显的Eu负异常以及?34SCDT值正偏等特征,这种独特的晶体形态和地球化学特征以及在空间上与水合物层或异常层间的分布关系均与祁连山冻土区天然气水合物成藏体系密切相关.由于气候变化是影响冻土区天然气水合物稳定性的一个重要因素,“裂隙型”黄铁矿可能是区域气候变暖背景下水合物发生次生变化的产物,其分布的密集程度反映了当水合物稳定带缩小时,底界处水合物分解最为强烈,而稳定带内水合物分解相对较弱,其分布的顶底界记录了天然气水合物稳定带曾存在的最大范围.
In the Qilian Mountains permafrost zone containing gas hydrate or presence of hydrate anomalous drilling core development of a semi-filled or fully filled rock fissure authigenic pyrite, “fissure type ” pyrite, its occurrence It has some similarities with the hydrate occurrences found in the area, and its distribution mainly concentrates in the lower part of the hydrate layer or anomalous layer. Through the study of gas hydrate drilling wells in the Qilian Mountains permafrost wells containing DK- Cracking type “pyrite core samples to carry out the pyrite morphology, trace, rare earth elements and sulfur isotope composition study found that ” fissure type “pyrite with a fractured orientation along the rock fracture surface cube shape Pyrite mainly with concomitant ”round “ structure, lower Co / Ni and Sr / Ba values, lower ΣREE content, LREE relative HREE enrichment and obvious Eu negative anomalies and? 34SCDT value positive The unique crystal morphology and geochemical characteristics as well as the spatial distribution of gas hydrate or anomalous layers are closely related to the gas hydrate accumulation system in the Qilian Mountains permafrost.As climate change is affecting the freezing Soil gas hydrate An important factor in qualitative analysis is that ”fissure-type" pyrite may be the product of secondary changes of hydrates in the background of regional climate warming. The intensity of distribution indicates that when the hydrate stability zone is reduced, The hydrate decomposition is the most intense, while the decomposition of hydrate in the stable zone is relatively weak. The top and bottom distributions of the distribution record the maximum range in which the gas hydrate stability zone once existed.