秦南凹陷石东陡坡带沙一段陆相混积岩地球化学特征及其地质意义

发布时间：2018-03-10 02:34

本文选题：地球化学特征　切入点：陆相混积岩　出处：《东北石油大学学报》2017年02期 　论文类型：期刊论文

【摘要】：为揭示渤海湾盆地秦南凹陷石东陡坡带秦皇岛29-A构造沙河街组一段陆相混积岩的形成条件和发育规律,在对混积岩岩石学分析基础上,利用元素地球化学方法,研究秦皇岛29-A构造地球化学特征、沉积环境和物源类型。结果表明:该构造B、Sr/Ba、Sr/Cu和Th/U等元素地球化学指标反映混积岩发育于干旱气候条件下的半咸水弱氧化沉积环境;为Ti/Zr、Cr/Zr低,LREE富集,HREE亏损的稀土元素配分模式,反映陆源碎屑以中酸性火成岩为主;MgO、CaO与SiO_2质量分数呈明显的负相关关系,揭示碳酸盐发育明显受陆源碎屑输入量控制,碳酸盐组分发育于陆源碎屑供给的间歇期;δEu正异常和较高的包裹体均一温度揭示它受到热液改造作用。研究区混积岩是以酸性火山岩为母岩的扇三角洲在陆源碎屑供给间歇期、于水体咸化浓缩蒸发环境下形成的,并且后期受到深部热液改造作用。
[Abstract]:In order to reveal the forming conditions and developing rules of continental migmatite in the first member of Shahejie formation in Qinhuangdao 29-A structure in Shidong steep slope belt of Qingnan depression, Bohai Bay basin, based on petrological analysis of migmatite, element geochemistry method is used. The structural geochemical characteristics, sedimentary environment and provenance types of 29-A in Qinhuangdao are studied. The results show that the geochemical indexes of elements such as BX Sr / Ban Sr / Cu and Th/U reflect the weakly oxidized sedimentary environment of brackish water developed in arid climate. The REE partition model for the low LREE enrichment of Ti / Zr / Cr / Zr shows that there is an obvious negative correlation between the SiO_2 mass fraction and the intermediate acid igneous rocks, which indicates that the carbonate development is obviously controlled by the terrigenous clastic input. The carbonate component developed during the intermission period of continental clastic supply, and 未 EU positive anomaly and higher homogenization temperature of inclusions revealed that it was subjected to hydrothermal transformation. The migmatite in the study area is a fan delta with acid volcanic rocks as its parent rock during the intermission of continental clastic supply. It was formed in the environment of saltwater concentration and evaporation and was transformed by deep hydrothermal solution in the later stage.
【作者单位】：中海石油(中国)有限公司天津分公司;
【基金】：国家科技重大专项(2016ZX05024-003-005)
【分类号】：P588.2;P618.13

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