|
|||||
|
|
Geochemistry and genesis of authigenic pyrite from gas hydrate accumulation system in the Qilian Mountain permafrost,Qinghai, northwest China |
|
| Authors: | PingKang Wang YouHai Zhu ZhenQuan Lu Xia Huang ShouJi Pang Shuai Zhang ShaoQing Jiang QingHai Li KaiLi Yang Bing Li |
| Institution: | 1. Oil and Gas Survey, China Geological Survey, Beijing, 100029, China 2. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, 100037, China 3. Chinalco Resources Corporation, Beijing, 100082, China 4. Qinghai No.105 Coal Geological Exploration Team, Xi’ning, 810007, China 5. The Training Brigade of Gold Headquarters of Chinese People’s Armed Police Force, Xiangyang, 441002, China 6. College of Construction and Engineering, Jilin University, Changchun, 130021, China |
| Abstract: | A type of authigenic pyrites that fully fill or semi-fill the rock fractures of drillholes with gas hydrate anomalies are found in the Qilian Mountain permafrost; this type of pyrite is known as “fracture-filling” pyrite. The occurrence of “fracture-filling” pyrite has a certain similarity with that of the hydrate found in this region, and the pyrite is generally concentrated in the lower part of the hydrate layer or the hydrate anomaly layer. The morphology, trace elements, rare earth elements, and sulfur isotope analyses of samples from drillhole DK-6 indicate that the “fracture-filling” pyrites are dominated by cubic ones mainly aligned in a step-like fashion along the surfaces of rock fractures and are associated with a circular structure, lower Co/Ni and Sr/Ba, lower ΣREE, higher LREE, significant Eu negative anomalies, and Δ34SCDT positive bias. In terms of the pyrites’ unique crystal morphology and geochemical characteristics and their relationship with the hydrate layers or abnormal layers, they are closely related with the accumulation system of the gas hydrate in the Qilian Mountain permafrost. As climate change is an important factor in affecting the stability of the gas hydrate, formation of fracture-filling pyrites is most likely closely related to the secondary change of the metastable gas hydrate under the regional climate warming. The distribution intensity of these pyrites indicates that when the gas hydrate stability zone (GHSZ) is narrowing, the hydrate decomposition at the bottom of the GHSZ is stronger than that at the top of the GHSZ, whereas the hydrate decomposition within the GHSZ is relatively weak. Thus, the zone between the shallowest and the deepest distribution of the fracture-filling pyrite recorded the largest possible original GHSZ. |
| Keywords: | authigenic pyrite fracture-filling gas hydrate accumulation system permafrost Qilian Mountain |
| 本文献已被 CNKI SpringerLink 等数据库收录！ | |