攀西地区基性—超基性岩岩石地球化学特征及岩浆演化过程分析
发布时间：2018-07-29 11:54
【摘要】：攀西基性-超基性岩体主要分布在扬子克拉通西缘,受南北向断裂带控制,隶属于峨眉山大火成岩省。岩体与峨眉山大火成岩省玄武岩形成时间均为晚二叠世,有一定相关性。本文选取攀西地区攀枝花、白马和红格三个区域的基性-超基性岩岩体作为典型代表,对其进行详细的野外地质观察、岩体地质特征、岩相学特征以及全岩主微量元素地球化学特征分析,以解释其岩浆演化的过程及与成矿的相关性。三个区域的含矿岩体在岩相带划分上略有不同,但总体上均表现出典型的韵律旋回特征。通过对三个代表岩体的不同岩石类型样品的全岩主量测试结果显示,它们均具有低硅,高钛、铁、镁、钙,低钠、钾的特征。Zr/Ti O2*0.0001vs.Si O2图解、Nb/Y vs.Zr/Ti O2*0.0001图解,AFM图解显现其属于略偏亚碱性的拉斑玄武岩系列岩石。三个区域的微量元素地球化学特征显示其富集轻稀土元素,亏损重稀土元素,富集部分大离子亲石元素(Th、U),亏损一些高场强元素(Zr、Hf),暗示了它们可能具有相同的岩浆源区,并且图解趋势与OIB洋岛玄武岩有强相似性。岩体Si O2(32.59 65.81%)含量变化较大,Mg O(多数介于0.85 9.29%)含量普遍较低,低Cr(6.43-295ppm)等特征显示其可能形成于相对演化的岩浆而并非地幔原生岩浆。微量元素特征显示出明显分异特征,强不相容元素较为富集,且微量元素蛛网图显示与丽江苦橄岩有一定相似性。丽江苦橄岩基本代表峨眉山玄武岩的原始岩浆,且其直接为地幔柱熔融结晶的产物,因此岩体的岩浆源区可能来自地幔柱。但是本文研究区岩体普遍不存在Nb、Ta的负异常,表明其地幔柱岩浆源区没有受到地壳物质的混染。岩体又均存在Zr和Hf元素负异常,表明岩浆在上升侵位过程中基本没有经历地壳物质的混染。岩体的Ti O2含量一般都高于2.5%,有时可高达8.44%,显示其类似于高钛玄武岩特征。Mg O与主要氧化物之间存在一定的相关性。Mg O与Ca O和Fe O呈正相关,而同时与Si O2和Al2O3表现为负相关,显示岩浆演化过程中发生了单斜辉石(无斜方辉石)的分离结晶。部分岩石样品中随着Mg O含量的降低,Na2O、Al2O3、Ti O2和Si O2含量升高,显示在超基性岩形成时以橄榄石的堆积为主,但是橄榄石一般仅存在于岩体底部,可能是分离结晶初期发生但并未在整个演化过程中起主要作用。Fe O与Ti O2正相关性,Al2O3和Ca O的无相关性,均表明岩浆演化过程中基本不存在斜长石的分离结晶。因此攀西岩体演化来源于地幔柱外围地幔来源的富钛铁玄武质岩浆。岩浆演化早期的富铁钛氧化物熔体向下集中,晚期岩浆再一次发生液态不混溶,从而结晶分异出岩体和矿体,并由重力作用影响最终聚集成矿。
[Abstract]:The basic-ultrabasic rock body of Panxi is mainly distributed in the western margin of Yangtze craton, controlled by the north-south fault zone, and belongs to the Emeishan great igneous province. The formation time of basalt in Emeishan igneous province is of late Permian, which is related to each other. In this paper, the basic-ultrabasic rock mass in Panzhihua, Baima and Hongge regions in Panzhihua, Panzhihua area and Hongge area is selected as the typical representative, and the detailed field geological observation and geological characteristics of the rock mass are carried out. In order to explain the process of magmatic evolution and the correlation with mineralization, the petrographic characteristics and the geochemical characteristics of the main trace elements in the whole rock are analyzed. The ore-bearing rock bodies in the three regions are slightly different in the division of lithofacies, but on the whole they all show typical rhythmic cycles. The main rock mass measurements of different rock types of the three represents rock mass show that they all have low silicon, high titanium, iron, magnesium, calcium and low sodium. The characteristics of potassium. Zr- / Ti O2*0.0001vs.Si O _ 2 diagram and NB / Y vs.Zr/Ti O _ 2O _ (0.0001) diagram show that it belongs to a slightly sub-alkaline tholeiite series. The geochemical characteristics of trace elements in the three regions indicate that they are enriched in light rare earth elements, depleted in heavy rare earth elements, enriched in some large ion lithophile elements (Thu) and depleted in some high field strength elements (ZrHf), suggesting that they may have the same magmatic source. The graphic trend is strongly similar to that of OIB basalt. The content of Sio _ 2 (32.59 ~ 65.81%) varies greatly (mostly between 0.85% and 9.29%), and the low Cr (6.43-295ppm) characteristics indicate that the Sio _ 2 (32.59 ~ 65.81%) may be formed from the relatively evolved magma rather than the mantle primary magma. The characteristics of trace elements show obvious differentiation, and the strongly incompatible elements are enriched, and the trace element spider webs show some similarity with the picrite in Lijiang. Lijiang picrite basically represents the primitive magma of Emeishan basalt and is directly the product of melting crystallization of mantle plume, so the magmatic source of the rock may come from mantle plume. However, there is no negative anomaly of NB ~ (2 +) Ta in the study area, which indicates that the mantle plume magmatic source area is not contaminated by crustal materials. There are also negative anomalies of Zr and HF elements in the rock mass, which indicates that the magma has not experienced crustal material mixing in the process of uplift emplacement. The content of TIO _ 2 in rock mass is generally higher than 2.5, and sometimes it can be as high as 8.44, which shows that there is a certain correlation between TIO _ 2 and main oxides, which is similar to that of high-titanium basalts. There is a positive correlation between MgO and Cao and Feo. At the same time, there is a negative correlation with Sio 2 and Al2O3, indicating that the separation and crystallization of clinopyroxene (no clinopyroxene) occurred during the magmatic evolution. The content of Na _ 2O _ 2O _ 3 Al _ 2O _ 3 TIO _ 2 and Sio _ 2 in some rock samples increases with the decrease of MgO content, indicating that olivine accumulation is dominant in the formation of ultrabasic rocks, but olivine usually exists only at the bottom of the rock mass. It is possible that the separation and crystallization occurred in the early stage of separation and crystallization but did not play a major role in the whole evolution process. There is no correlation between Fe O and TIO 2 positive correlation between Al 2O 3 and Cao, indicating that there is no separation and crystallization of plagioclase during magmatic evolution. Therefore, the evolution of Panxi pluton originated from the Black Tortoise magma rich in titanium from the mantle around the mantle plume. In the early stage of magmatic evolution, the iron-rich titanium oxide melts concentrate downwards, and the late magma once again produces liquid immiscible solution, thus crystallizing and differentiating the rock bodies and orebodies, and finally aggregating and forming ore bodies by the influence of gravity.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1
本文编号：2152600
[Abstract]:The basic-ultrabasic rock body of Panxi is mainly distributed in the western margin of Yangtze craton, controlled by the north-south fault zone, and belongs to the Emeishan great igneous province. The formation time of basalt in Emeishan igneous province is of late Permian, which is related to each other. In this paper, the basic-ultrabasic rock mass in Panzhihua, Baima and Hongge regions in Panzhihua, Panzhihua area and Hongge area is selected as the typical representative, and the detailed field geological observation and geological characteristics of the rock mass are carried out. In order to explain the process of magmatic evolution and the correlation with mineralization, the petrographic characteristics and the geochemical characteristics of the main trace elements in the whole rock are analyzed. The ore-bearing rock bodies in the three regions are slightly different in the division of lithofacies, but on the whole they all show typical rhythmic cycles. The main rock mass measurements of different rock types of the three represents rock mass show that they all have low silicon, high titanium, iron, magnesium, calcium and low sodium. The characteristics of potassium. Zr- / Ti O2*0.0001vs.Si O _ 2 diagram and NB / Y vs.Zr/Ti O _ 2O _ (0.0001) diagram show that it belongs to a slightly sub-alkaline tholeiite series. The geochemical characteristics of trace elements in the three regions indicate that they are enriched in light rare earth elements, depleted in heavy rare earth elements, enriched in some large ion lithophile elements (Thu) and depleted in some high field strength elements (ZrHf), suggesting that they may have the same magmatic source. The graphic trend is strongly similar to that of OIB basalt. The content of Sio _ 2 (32.59 ~ 65.81%) varies greatly (mostly between 0.85% and 9.29%), and the low Cr (6.43-295ppm) characteristics indicate that the Sio _ 2 (32.59 ~ 65.81%) may be formed from the relatively evolved magma rather than the mantle primary magma. The characteristics of trace elements show obvious differentiation, and the strongly incompatible elements are enriched, and the trace element spider webs show some similarity with the picrite in Lijiang. Lijiang picrite basically represents the primitive magma of Emeishan basalt and is directly the product of melting crystallization of mantle plume, so the magmatic source of the rock may come from mantle plume. However, there is no negative anomaly of NB ~ (2 +) Ta in the study area, which indicates that the mantle plume magmatic source area is not contaminated by crustal materials. There are also negative anomalies of Zr and HF elements in the rock mass, which indicates that the magma has not experienced crustal material mixing in the process of uplift emplacement. The content of TIO _ 2 in rock mass is generally higher than 2.5, and sometimes it can be as high as 8.44, which shows that there is a certain correlation between TIO _ 2 and main oxides, which is similar to that of high-titanium basalts. There is a positive correlation between MgO and Cao and Feo. At the same time, there is a negative correlation with Sio 2 and Al2O3, indicating that the separation and crystallization of clinopyroxene (no clinopyroxene) occurred during the magmatic evolution. The content of Na _ 2O _ 2O _ 3 Al _ 2O _ 3 TIO _ 2 and Sio _ 2 in some rock samples increases with the decrease of MgO content, indicating that olivine accumulation is dominant in the formation of ultrabasic rocks, but olivine usually exists only at the bottom of the rock mass. It is possible that the separation and crystallization occurred in the early stage of separation and crystallization but did not play a major role in the whole evolution process. There is no correlation between Fe O and TIO 2 positive correlation between Al 2O 3 and Cao, indicating that there is no separation and crystallization of plagioclase during magmatic evolution. Therefore, the evolution of Panxi pluton originated from the Black Tortoise magma rich in titanium from the mantle around the mantle plume. In the early stage of magmatic evolution, the iron-rich titanium oxide melts concentrate downwards, and the late magma once again produces liquid immiscible solution, thus crystallizing and differentiating the rock bodies and orebodies, and finally aggregating and forming ore bodies by the influence of gravity.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1
【参考文献】
相关期刊论文 前2条
1 李佑国;许家斌;张月姣;王雪;;红格矿床地质地球化学特征与岩浆演化[J];矿物学报;2013年S2期
2 汪云亮,张成江,修淑芝;玄武岩类形成的大地构造环境的Th/Hf-Ta/Hf图解判别[J];岩石学报;2001年03期
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