东秦岭燕山期成矿小斑岩体成因机制及构造背景

发布时间：2018-06-22 22:47

本文选题：东秦岭 + 成矿小斑岩体　；参考：《西北大学》2015年硕士论文

【摘要】：东秦岭钼矿带主要分布于秦岭造山带的华北板块南缘地区以及北秦岭地区,区域内与钼多金属成矿关系密切的主要为浅成-超浅成中酸性小斑岩体,关于这些成矿小斑岩体的形成时代、成因机制以及构造背景的研究目前仍存有较大争议与薄弱之处。本文选取华北板块南缘及北秦岭地区多个具有典型成矿作用的浅成-超浅成中酸性小斑岩体作为重点研究对象,其中包括华北南缘地区石家湾岩体、黑山村岩体、木龙沟岩体以及北秦岭地区蟒岭岩体西侧的南台岩体、桃官坪岩体、西沟岩体、高沟岩体、牛家湾岩体、腰庄村岩体,对其进行系统的野外地质调查、岩相学、年代学及元素地球化学等方面的研究。本文通过锆石U-Pb定年获得的华北南缘地区石家湾岩体、黑山村岩体、木龙沟岩体的年龄分别为140.9±1.6Ma、148.6±1.2Ma、140.4±1.2Ma,北秦岭地区蟒岭岩体西侧的桃官坪岩体、西沟岩体、高沟岩体、牛家湾岩体、腰庄村岩体的年龄分别为147.1±.lMa、147.2±1.3Ma、148.5±1.2Ma、143.95±0.91Ma、147.1±.lMa,上述成矿小斑岩体的形成年龄介于140.4±1.2Ma-148.6±1.2Ma之间,属于晚侏罗世-早白垩世,与整个东秦岭地区燕山期花岗质岩体的形成时代一致(120Ma～160Ma),为东秦岭地区燕山期构造-岩浆活动的产物。元素地球化学特征显示,研究区岩体具有高硅(64.70%-75.20%),富碱(K2O+Na2O=6.78%～9.79%)的特征,属准铝质-弱过铝质、高钾钙碱性/钾玄岩系列,具有I-A过渡型花岗岩特征；多数稀土元素配分曲线具右倾特征,呈弱的Eu负异常或微弱正Eu异常；富集LILE元素：Cs、Rb、Ba、K、Sr等,而相对亏损HFSE元素：Nb、Ta、Zr、P、Ti等。结合前人对锆石Hf同位素研究成果表明,研究区岩体的物源表现为以壳源为主并混有一定的幔源组分,其源区存在于深度大于40Km的地壳深处。通过对成岩年龄特征、地球化学特征、物质来源特征等方面对比研究表明：1.东秦岭燕山期成矿小斑岩体与花岗质大岩基两类不同产出方式的岩体具有相同源区性质及成因机制。2.东秦岭与大别两个地区燕山期花岗质岩体是在同一相似构造背景下产生的花岗质岩浆活动分别在这两个不同地区浅部位置侵位的产物。综合分析认为,秦岭-大别造山带燕山期岩浆活动的构造背景与华北板块南部向秦岭-大别造山带的陆内俯冲作用有关,沿该条贯通东西的巨型陆内俯冲带,相应的形成了陆缘岩浆活动产物-从东秦岭至大别两个不同地区呈东西向带状大规模分布的燕山期花岗质岩体。
[Abstract]:The East Qinling molybdenum ore belt is mainly distributed in the southern margin of the North China plate and the North Qinling area of the Qinling orogenic belt. At present, there are still some controversies and weaknesses in the study of the formation age, genetic mechanism and tectonic background of these ore-forming small porphyry bodies. In this paper, several epigenetic and ultra-shallow intermediate-acid porphyry bodies with typical mineralization in the southern margin of North China plate and North Qinling region are selected as the main research objects, including Shijiawan rock body and Keshancun rock mass in the southern margin of North China. Mulonggou rock body and the south platform rock mass, Taoganping rock body, Xigou rock body, Gaogou rock body, Niujiawan rock mass, Yaozhuang village rock mass in the west side of the pyengling rock mass in the north Qinling area, are systematically investigated in the field, and their petrography, etc. Studies on geochronology and element geochemistry. Through zircon U-Pb dating, the ages of Shijiawan, Heishancun and Mulonggou in the southern margin of North China are 140.9 卤1.6 Ma-148.6 卤1.2 Ma-140.4 卤1.2 Ma. the Taoganping, Xigou, Gaogou, Niujiawan and Niujiawan pluton in the west side of the Xigou rock body, northern Qinling area, are obtained respectively. The age of the Yaozhuangcun rock body is 147.1 卤.lMa-147.2 卤1.3Ma-148.5 卤1.2Ma-143.95 卤0.91Ma-147.1 卤.lMa.The age of the ore-forming small porphyry body is between 140.4 卤1.2 Ma-148.6 卤1.2 Ma, which belongs to the late Jurassic-early Cretaceous, and the age of the ore-forming small porphyry body is 140.4 卤1.2 Ma-148.6 卤1.2 Ma, which belongs to the late Jurassic to early Cretaceous. It is consistent with the Yanshanian granitic body formation age (120 Ma-160 Ma) in the whole East Qinling area and is the product of the Yanshanian tectonic-magmatic activity in the East Qinling area. The elemental geochemical characteristics show that the study area is characterized by high silicon (64.70-75.20%) and alkali rich (K _ 2O Na _ 2O _ 2O _ 6. 78 ~ 9.79%), which belongs to the quasi-aluminite-weak peraluminous, high-potassium calc-alkaline / kalmonite series and is characterized by I-A transitional granites. Most of the REE partitioning curves have the characteristics of right deviation, weak negative EU anomaly or weak positive EU anomaly, and enrichment of Lile element 1: Csl, Rslb, Baan, Ku, Sr, etc., while the relative depletion of HFSE element: NbSe, Tazrzru, Pnu, Ti and so on. In combination with previous studies on zircon HF isotopes, it is shown that the source of the rock mass in the study area is mainly crust source and mixed with certain mantle source, and its source exists in the deep crust with depth greater than 40 km. A comparative study of diagenetic age, geochemistry and material source shows that: 1. The ore-forming small porphyry body and granitic rock base of Yanshanian period in East Qinling have the same source property and genetic mechanism. The Yanshanian granitic intrusions in the East Qinling and Dabie regions are the result of the emplacement of granitic magmatism in the shallow part of the two regions in the same similar tectonic setting. It is concluded that the tectonic setting of Yanshanian magmatic activity in the Qinling Dabie orogenic belt is related to the intracontinental subduction of the southern North China plate toward the Qinling Dabie orogenic belt, along the east-west giant intracontinental subduction zone. Corresponding to the formation of the continental margin magmatic activity products-from the East Qinling to Dabie two different areas of east-west zonal large-scale distribution of Yanshanian granitic rocks.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.2;P581

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