夏子街组特殊岩性段地球物理特征及其成因  

The Special lithologic Sections of Permian Xiazijie Formation in Junggar Basin: Geophysical Characteristics and Origin

作　　者：毛志强[1,2] 申波[1,2] 匡立春[3] 孙中春[3] 罗兴平[3] 

机构地区：[1]中国石油大学地球物理与信息工程学院,北京102249 [2]中国石油大学地球探测与信息技术北京市重点实验室,北京102249 [3]中国石油新疆油田分公司勘探开发研究院,新疆克拉玛依834000

出　　处：《新疆石油地质》2013年第1期98-100,共3页Xinjiang Petroleum Geology

摘　　要：准噶尔盆地上二叠统夏子街组存在异常自然伽马呈交互段产出的"特殊岩性段",其分布与区域断裂构造有关。井壁电阻率成像测井指示,异常高自然伽马层段主要出现在裂缝发育带及砂砾岩底部冲刷面。分析认为,"特殊岩性段"异常高自然伽马是由富含放射性同位素的凝灰岩、流纹岩及安山岩等火山岩母岩碎屑重新分配的结果。岩石薄片鉴定结果表明,"特殊岩性段"存在水云母、铁白云石及黄铁矿等多种典型的热液蚀变矿物。综合分析认为,"特殊岩性段"是由深部热液沿断裂上升至沉积层而形成的热液蚀变体,推测"特殊岩性段"内异常高自然伽马是热液溶解母岩碎屑中铀同位素后沿热液活动通道运移并再次富集沉滨的结果。According to the GR log response, the special lithologic sections could be easily identified from the sandy conglomerates in Permian Xiazijie formation of Junggar basin, in which the GR log shows alternate abnormal high GR and low GR responses. The 3D seismic and dip log show that the distribution of the special lithologie sections is spatially related to the regional fault. The borehole resistivity image indicates that the abnormal high GR within the special lithologic sections usually located in naturally fractured zone or in the erosion surface in bottom of sandy conglomerates. The statistical analysis of GR log values manifests that the average value of GR of the special lithologic sections is close to that of Xiazijie formation with normal GR response. It is consequently supposed that the abnormal high GR in the specail lithologic sections mainly results from the redistribution of radioisotopes of the fragmental deposits within the formation. Several typical minerals such as hydromica, ankerite and pyrite have been identified by thin section analysis from rock samples of the special lithologic sections. Therefore, it is concluded that the identified special lithologic sections in Permiean Xiazijie formation are hydrothermal altered bodies caused by hydrothermal alteration conducted by hydrothermal fluids coming from the deep regional fault. This paper puts forward the hypothesis that the abnormal high GR reading in the special lithologic sections mainly created by the precipitations of uranium isotopes dissolved and migrated bythe hydrothermal fluids related to various permeable bodies, that is, faults, fractured formation and erosion surfaces.

关 键 词：准噶尔盆地 二叠系 特殊岩性段 自然伽马 成因 热液蚀变体 

分 类 号：P631.84[天文地球—地质矿产勘探]