大渡河金成矿带基性—超基性脉岩形成时代及成因探讨

发布时间：2018-01-24 20:15

本文关键词： 大渡河基性-超基性岩脉形成时代成因　出处：《成都理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：大渡河金成矿带位于扬子地台西缘,康定大渡河两岸。在大地构造位置上位于松潘-甘孜造山带与川滇南北向构造带及西南三江造山带的过渡地带。大渡河金成矿带的基性—超基性脉岩主要是辉绿岩,这些辉绿脉岩在大渡河金成矿带中多个典型金矿床均发现出露(包括黄金坪、韭菜坪、白金台子、一柱香、二里沟、康定金矿等)。并且辉绿岩在空间分布上存在密切关系。论文以大渡河金成矿带基性-超基性岩脉形成时代与成因探讨为重点,通过矿床地质特征、地球化学特征、成矿时代、岩脉年代学以及前人的一些研究成果分析对比等方面研究对大渡河流域多个典型金矿中采集的辉绿岩进行探讨,通过研究得出以下认识：(1)大渡河金成矿带在经历了前震旦纪基底形成阶段,震旦纪到中三叠世时期内,被动大陆边缘从起始到发展,晚三叠世-白垩纪碰撞造山阶段和新生代陆内造山阶段。这些有利的地质构造运动为研究区域内的岩浆活动提供了有利的动力来源,物质来源以及运移通道。根据锆石U-Pb测试数据,得出大渡河金成矿带基性-超基性岩脉可以分为三个期次,第一期为754Ma,如姑咱-长河坝辉绿岩脉；第二期为430Ma,如偏岩子辉绿岩脉；第三期为220Ma,如二里沟、一柱香辉绿岩脉。三个期次基性-超基性岩脉具有一定的分布规律,即在基底中出露的基性-超基性岩脉除白金台子和极少数形成较早的基性岩脉外均在220Ma左右形成,而在盖层中的基性-超基性岩脉形成时代均为430Ma左右。(2)由于大渡河金成矿带构造环境的复杂性和多期性,促成该地区岩浆活动较为活跃,根据对该地区的基性-超基性岩脉岩石化学性质的差异的分析可以将三个期次的基性-超基性岩脉划分为两种成因类型,第一种属于岛弧火山环境下形成的基性岩脉,其形成时期大都在220Ma,其动力来源于板块间的俯冲碰撞,物质来源于俯冲板片脱水交代地幔熔融通过由于板块俯冲形成的断裂带上涌形成,这类基性岩脉绝大多数存在于基底地层中。第二种成因机制类似于MORB,是板内裂谷拉张所形成的,这一组基性岩脉年龄在430Ma左右,其物质来源于软流圈地幔,通过拉张环境形成的断裂上涌熔融形成,这类基性岩脉出露于盖层地层中。(3)大渡河基性-超基性岩脉的岩石化学特征表明,这些基性-超基性岩脉的物质来源于深部地壳或上地幔,基性岩脉的出现指示了其所在位置曾发生过深达下地壳或上地幔的拉张作用,说明大渡河断裂是深达下地壳或上地幔的深大断裂。在区域性拉张的环境下,不仅有利于深部地壳或上地幔的基性-超基性岩浆侵入,同样有利于深部热液流体运移。同样,前人研究表明金元素在浅部地壳的初始丰度非常低,地壳中的金绝大部分来源于深部地壳或上地幔。在野外地质调查中发现,该地区多数金矿床/体同基性-超基性岩脉在空间上存在着密切的关系,根据项目组所测得的大渡河金成矿带上的金矿床/体的年龄在5～50Ma范围内,远迟于该地区基性-超基性岩脉的形成时代,所以形成金矿的含金热液流体可能是沿用了基性-超基性岩浆运移通道。
[Abstract]:The Dadu River gold metallogenic belt is located in the western margin of the Yangtze platform, Kangding Dadu River. The tectonic position is located in Sichuan and Yunnan north-south tectonic zone and transition zone of southwestern Sanjiang orogenic belt of Songpan - Ganzi orogenic belt. The Dadu River metallogenic belt of mafic - ultramafic dikes are mainly diabase, the diabase dikes in the Dadu River gold metallogenic belt of several typical gold deposits were found in the exposed (including Huangjinping, Jiucaiping, platinum table, incense, gold and so on. The second gully, Kangding) and diabase has close relationship in spatial distribution. Based on the Dadu River metallogenic belt of mafic ultramafic dikes formed age and Genesis of the focus, through the geological characteristics, geochemical characteristics, metallogenic epoch, the acquisition of several typical gold deposits in the Dadu River Valley of diabase dikes on geochronology and some previous research results of comparative analysis etc. To know through the research as follows: (1) the Dadu River gold metallogenic belt experienced in the pre Sinian basement formation stage, the Sinian to Triassic in the three period, from the beginning to the development of the passive continental margin, three of Late Triassic Cretaceous orogenic stage and Cenozoic intracontinental orogenic stage. These favorable tectonic movement provides a source of power for the study area of magmatic activities, material source and migration channel. According to the zircon U-Pb test data, the Dadu River metallogenic belt of basic ultrabasic veins can be divided into three stages the first stage is 754Ma, such as guzan - Changheba diabase; second for a period of 430Ma, such as pianyanzi diabase; the third period is 220Ma, such as the two groove diabase. Incense, a three stage sub ultrabasic rock veins have a certain distribution, namely basic and ultrabasic rocks exposed in the basement in platinum veins The table and a handful of forming mafic dikes earlier formed were about 220Ma, while in the cover layer in the mafic ultramafic dikes formed are about 430Ma. (2) because of the complexity of the tectonic environment of the Dadu River gold metallogenic belt and multi period, contributed to the magmatic activity in this area is more active, according to the analysis the difference of rock chemical properties of mafic ultramafic dikes of the area can be three times the basic ultrabasic veins are divided into two types, the first formation belongs to the island arc volcano under the environment of the formation of mafic dikes, mostly in the period of 220Ma, its power comes from the subduction and collision of the plates that material from the subduction melting of the metasomatized mantle through subduction due to fracture zone formed by upwelling formation, these mafic dikes exists in the vast majority of the basement strata. Second kinds of genetic mechanism similar to MORB, is the intraplate pull A form, this group of mafic dikes at the age of about 430Ma, the substances derived from the asthenospheric mantle, formed by fracture extensional environment formed by upwelling melting, the mafic dykes outcropped in the covering strata. (3) showed that the geochemical characteristics of mafic ultramafic rocks in the Dadu River dikes and these basic ultrabasic veins material from deep crust or upper mantle, appear mafic dikes indicate that their position had a depth of the lower crust or upper mantle tension, indicating the Dadu River fault is a deep fault depth of the lower crust or upper mantle. In regional extensional environment next, not only the base for deep crust or upper mantle ultrabasic magmatic intrusion, also conducive to the deep hydrothermal fluid migration. Also, previous studies show that the gold element in the initial abundance of shallow crust is very low, the crust of the gold from the vast majority of deep Crust or upper mantle. Found in field geological survey, the majority of gold deposits in the area / body have the same basic ultrabasic veins in space are closely related, according to the gold mineralization of Dadu River measured project group with the gold deposit / body age in the range of 5 ~ 50Ma, far late in the area of mafic ultramafic dikes formed the era, so the formation of gold bearing hydrothermal fluid may be used for basic ultrabasic magma transportation channel.

【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P618.51;P588.12

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