临南洼陷侵入岩对围岩有机质演化及地球化学特征的影响

发布时间：2018-05-02 22:18

本文选题：侵入体 + 围岩　；参考：《山东科技大学》2017年硕士论文

【摘要】：临南洼陷位于惠民凹陷的西南部,受新生代断陷的影响,区内岩浆活动剧烈,发育大量侵入体。本文以临南洼陷夏38块侵入体为研究对象,明确了侵入体的岩石学和地球化学化学特征,分析了侵入体对围岩地层的影响及原因,阐明了围岩受影响范围。通过野外岩心观察、薄片镜下鉴定和岩石主微量元素分析等确定:夏38块侵入体岩性以辉绿岩为主,也可见少量玄武岩;岩浆偏碱性,具有贫钾富钠的特征;微量元素分析显示火成岩属于板内裂谷型玄武岩;稀土元素分析,岩浆源区熔融程度相对较高,岩浆来自较深的地幔源区,且在形成过程没有发生明显分异;锶钕同位素分析显示,岩浆源区主要两个,一个为具DMM或似印度洋MORB特征的源区,另一个为EM1,另外EM2也可能有一些贡献,但是较小。通过分析围岩的有机碳含量、镜质体反射率等,确定侵入岩促进围岩有机质生烃演化,使有机质含量减少,成熟度增高。根据围岩热传导规律建立了三种侵入岩热作用模式,确定了侵入岩周围温度场的分布,和侵入体热作用对围岩的影响范围。利用实测镜质体反射率数据恢复围岩最高古地温,对三种侵入岩热作用模式进行验证,表明夏38侵入体的热传导模式以简单热传导为主。通过野外岩心观察、薄片镜下鉴定、粘土矿物含量分析和同位素测定发现:侵入岩造成围岩粘土矿物转化异常;促进碳酸盐胶结物生成;围岩87Sr/86Sr明显降低。高温、流体物质及幔源CO2共同作用下造成了围岩粘土矿物转化异常;岩浆水、变质水、以及幔源CO2的共同影响了围岩碳酸盐胶结物的形成;侵入岩与围岩接触带附近裂隙中的蚀变流体是导致围岩87Sr/86Sr降低的主要原因。
[Abstract]:Linnan sag is located in the southwest of Huimin sag. Influenced by Cenozoic fault depression, magmatic activity is intense and a large number of intrusive bodies are developed in the area. Taking Xia-38 intrusions in Linnan sag as the research object, the petrological and geochemical chemical characteristics of intrusions are clarified, the influence of intrusions on surrounding rock strata and its causes are analyzed, and the affected range of surrounding rocks is clarified. Through field core observation, microscopical identification and analysis of main trace elements of rock, it is confirmed that the lithology of Xia-38 intrusive body is mainly diabase, and a small amount of basalt can also be seen, the magma is alkalescent and has the characteristics of poor potassium and sodium rich, and so on. Trace element analysis shows that igneous rocks belong to intraplate rift type basalt, REE analysis shows that the melting degree of magma source region is relatively high, magma comes from deeper mantle source region, and there is no obvious difference in the formation process. Strontium-neodymium isotopic analysis shows that there are two major magmatic sources, one with DMM or Indian Ocean MORB characteristics, the other with EM1, and EM2 may make some contributions, but it is small. By analyzing the organic carbon content and vitrinite reflectance of surrounding rock, it is determined that the intrusive rock promotes the hydrocarbon generation evolution of surrounding rock organic matter, reduces the organic matter content and increases the maturity. According to the heat conduction law of surrounding rock, three thermal models of intrusive rock are established, and the distribution of temperature field around intrusive rock and the influence range of intrusive body heat on surrounding rock are determined. By using the measured vitrinite reflectance data to recover the highest paleo-geothermal temperature of surrounding rock, three thermal models of intrusive rock are verified, which indicates that the heat conduction mode of Xia-38 intrusive body is mainly simple heat conduction. Through field core observation, thin slice microscopic identification, clay mineral content analysis and isotopic determination, it is found that intrusive rocks cause abnormal transformation of clay minerals in surrounding rock, promote formation of carbonate cement, and decrease 87Sr/86Sr of surrounding rock obviously. Under the action of high temperature, fluid material and mantle-derived CO2, the transformation anomaly of surrounding rock clay minerals is caused, and the formation of carbonate cementation in surrounding rock is influenced by magmatic water, metamorphic water and mantle-derived CO2. The alteration fluid in the fissure near the contact zone between intrusive rock and surrounding rock is the main reason for the decrease of 87Sr/86Sr in surrounding rock.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P584

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