四川德格雀儿山岩体岩石学、岩石地球化学特征及成因探讨

发布时间：2018-06-18 04:56

本文选题：雀儿山岩体 + 岩石地球化学特征　；参考：《成都理工大学》2015年硕士论文

【摘要】：雀儿山花岗岩体位于四川省西北部德格县境内,紧邻西藏自治区,总体属北东高南西低的典型高山深切割区。雀儿山岩体侵入于德格-乡城大断裂与甘孜-理塘深断裂交汇的三角地带的二叠系及上三叠统板岩、变砂岩中,被古近系沉积岩不整合覆盖,岩体以不规则复杂形态的岩基产出。虽然前人对雀儿山岩体的区域地质调查和研究已取得了较多成果,也有相关的专著出版和文章发表,但通过本次论文对雀儿山岩体的野外地质调查发现,前人研究对于该岩体侵入区域的地质、构造及演化历史,以及区域主要断裂的延伸、性质、几何学与运动学特征及其形成演化过程等的研究,尚缺少足够的实际资料和数据支撑。特别是关于雀儿山岩体与成矿作用的关系问题,尚显得十分薄弱。有鉴于此,本论文以雀儿山岩体的岩石学、岩石地球化学及其成因研究为选题,试图通过对岩体深入的野外地质调查、系统的岩石样品采集、测试和镜下鉴定,对雀儿山岩体进行解剖研究,力求深入掌握雀儿山岩体岩石类型及其宏观微观岩石学特点、侵入期次。特别是通过岩石地球化学特征研究,分析判断雀儿山岩体侵入的大地构造属性,进而探讨岩体就位机制。通过对雀儿山岩体及邻区其他酸性岩体的对比研究,重点了解研究区与酸性深成岩体有关的矿床(矿点)的矿种、类型、规模,适当开展矿床学、矿床地球化学研究,寻求矿床与岩体二者的关联性,进而归纳岩体成矿专属性,为区域上寻找与酸性岩体有关的矿产资源提供基础数据支持。雀儿山岩体大地构造上位于羌塘-三江造山系一级构造单元内甘孜-理塘弧盆系二级构造单元,隶属于义敦-沙鲁里岛弧带三级构造单元。该岛弧带又称义敦岛弧,也有称昌台-乡城岛弧带,以居德来-定曲、木龙-黑惠江断裂和甘孜-理塘蛇绿混杂岩带的马尼干戈-拉波断裂为其东界,包括义敦-白玉-乡城-稻城及三江口地区。义敦-沙鲁里岛弧是在中咱地块东部被动陆缘基础上,于晚三叠世早中期受甘孜-理瑭洋向西俯冲制约形成。义敦-沙鲁里岛弧带深成岩浆活动规模较大,构成非常醒目的带状岩浆弧,可以分为东西两个亚带。东亚带侵入岩浆活动的时代为237.5-208.0Ma,侵位形成与晚三叠世岛弧火山岩同期异相,岩石类型以中粗粒斑状二长花岗岩为主,次为花岗闪长岩,少量闪长岩、闪长玢岩、花岗斑岩等,从早到晚岩石为闪长岩→花岗闪长岩→二长花岗岩→花岗岩→花岗斑岩,亦即向酸碱质增高、钾钠比增大的方向演化。尤其是东亚带南段的部分二长闪长玢岩-花岗斑岩小岩体(年龄208-235Ma)控制了斑岩型铜矿床的生成,如普朗特大型斑岩型铜矿、雪鸡坪中型斑岩型铜矿等。后碰撞造山期花岗岩年龄为208-138Ma,主要岩石类型为二云母花岗岩和钾长花岗岩,次为二长花岗岩和二长闪长岩,叠加在俯冲期花岗岩带之上,主要发育于岛弧带的北段,是西南三江中段北带有色和贵金属成矿区形成的地质构造条件。雀儿山岩体就是在这样的构造背景下侵入形成。本论文研究区地层属羌塘-三江地层大区下的巴颜喀拉地层区的德格-中甸(香格里拉)地层小区。岩体附近出露地层主要有上三叠统图姆沟组(T3t)、喇嘛垭组(T3lm)以及第四系沉积物。雀儿山花岗岩体出露岩石类型,主要似斑状黑云母二长花岗岩、二长花岗岩、似斑状二长花岗岩、黑云母花岗岩、石英闪长岩等。本文通过对岩石的常量、微量、稀土元素测试发现,岩石SiO2含量普遍在63.29%-79.16%,Al2O3含量变化在10.50%-15.21%之间,根据SiO2与常量元素氧化物(Al2O3、CaO、Na2O、K2O、TiO2等)关系图解,闪长岩样品均落于高钾钙碱性系列区域,其余花岗岩类样品则落于高钾钙碱性系列和钾玄岩系列区域。在微量元素方面总体有相似的微量元素原始地幔标准化分布模式,岩石亏损大离子亲石元素Ba、Sr,P、Ti,不相容元素Rb、Th、U、K、Hf在岩体中富集。再结合Nb*、K*、Sr*、Zr*比值,推断雀儿山花岗岩基应属于岛弧带与碰撞造山有关的构造背景下侵位。稀土元素总体特点,ΣREE介于110.407-409.238之间,平均值为236.956;LREE介于82.798-378.822之间,平均值为211.268;HREE介于13.232-39.831之间,平均值25.688;LREE/HREE介于2.621-18.893之间,平均值为8.505;(La/Yb)N比值均大于1;Eu负异常显著(普遍δEu1);Ce无明显异常(δCe≈1),指示雀儿山岩体为碱性较高酸性岩体,应属于典型地壳重熔“S”型花岗岩。根据稀土、微量元素蛛网图、常量元素构造环境判别图,也显示出雀儿山花岗岩基就位机制在火山弧-同碰撞构造环境中。岩体形成的同位素年龄为102.23±0.91Ma。雀儿山岩体及邻区已发现的矿床主要为热液型、矽卡岩型以及斑岩型矿床,雀儿山岩体二长花岗岩、钾长花岗岩为主构成的岩石单元与稀土矿床有关。以钾长花岗岩或K2ONa2O的碱长花岗岩单元与W、Sn、Mo、Bi、Be矿化有关。以Na2OK2O的碱长花岗岩组成的单元与Nb、Ta矿化有关。以黑云母花岗岩为主构成的单元与稀土、W、Sn矿有关。以二云母花岗岩为主组成的单元与W、Sn、Mu、Bi、Be有关。以白云母花岗岩为主构成的单元与Be、Nb、Li、Ta、Rb等矿化有关。本论文发现的围岩蚀变类型包括:钾长石化→钠长石化→云英岩化→角岩化。本论文研究认为,雀儿山花岗岩基内及其围岩接触带有寻找上述矿种的矽卡岩、角岩型及云英岩型矿床的可能。
[Abstract]:The Nestle mountain granite body, located in dege County, northwest of Sichuan Province, is close to the Tibet autonomous region and belongs to the typical North East High South West low deep cutting area. The Nestle mountain intrusion is intruded on the Permian and upper three Permian slates in the triangle zone between the DGE Xiangcheng big fault and the Ganzi Litang deep fault, and in the sandstone, the Paleogene sedimentary rocks are changed. Unconformities covered, rock mass produced in irregular and complex forms. Although many achievements have been made in the regional geological investigation and research of the rock mass of the fours mountain, some published publications and articles have been published. The study of geological, tectonic and evolutionary history, and the extension of major faults in the region, properties, geometric and kinematic characteristics and their formation and evolution process are still lacking sufficient actual data and data support. In particular, the relationship between the rock mass and the mineralization of the fill mountain is still very weak. The study of rock petrology, rock geochemistry and genesis of rock mass is selected as a topic. Through an in-depth field geological survey of rock mass, systematic rock sample collection, test and microscopic identification, an anatomical study of the rock mass of the sill mountain is carried out in order to grasp the rock types of the rock mass in the rock mass of the Mt. Through the study of geochemical characteristics of rock and geochemistry, the geodetic properties of the intruding of the rock mass in the sill mountain are analyzed and judged, and then the mechanism of rock mass is discussed. Through the comparison of the rock mass and other acidic rock mass in the adjacent area, the mineral deposits (ore points) related to the acid deep rock mass, the type, the scale, and the proper development of the ore are discussed. The geochemical study of the deposit and the mineral deposit seeks the association between the two elements of the ore deposit and the rock mass, and then generalizes the special properties of the rock mass, and provides the basic data for the mineral resources related to the acid rock mass. The rock mass geodetic is located in the two grade structure of the Ganzi Litang arc basin system in the first tectonic unit of the Qiangtang Sanjiang orogenic system The unit, which belongs to the three level tectonic unit of the Yun - Sha Lu island arc belt, is also known as the Yun island arc, also known as the Changtai - Xiangcheng island arc belt, with the Gudai - Ding Qu, the Mong - Heihui River fault and the mani - ge - La - Po fault in the Ganzi - Litang OPHIOLITIC MELANGE belt to the East, including Yun - Bai Yu - Xiang City Daocheng and Sanjiang mouth areas. The shabumi island arc is based on the passive continental margin of the east of the central Zan massif and was formed by the Ganzi - neo - oceanic subduction in the early and middle period of the late three fold. The Yun - Sha Lu island arc zone has a large scale of deep magmatic activity, forming a very awakening banded magmatic arc and can be divided into two subzones of East and West. The era of intruding magmatic activity in East Asia zone is 237.5-2 08.0Ma, the formation of emplacement and late three superposition of the island arc volcanic rocks in the same period, the rock type is mainly the medium coarse grained two long granite, the second is granodiorite, a small amount of diorite, diorite porphyrite and granite porphyry, and from early to late, the rocks are diorite, granodiorite, two long flower granitic rock, granite and granite porphyry. In particular, the part of the two long diorite porphyry porphyry porphyry porphyry rock mass (age 208-235Ma) in the southern part of the East Asia zone controls the formation of porphyry copper deposits, such as the plutt large porphyry copper deposit and the medium porphyry copper deposit in the snow chicken Ping. The post collision orogenic granites are 208-138Ma and the main rock type is two. The mica granite and the potassium feldspar are two and two long diorite, superimposed on the subduction granite belt, mainly in the northern section of the island arc belt, which are the geological conditions for the formation of the nonferrous and noble metal metallogenic zone in the North Zone of the middle section of the southwest Sanjiang. The area of the study area belongs to the DGE Zhongdian (Shangri-La) stratigraphic plot in the Bayan La stratigraphic area under the Qiangtang Sanjiang stratigraphic area. The outcropping strata near the rock mass are mainly the upper three series of the Tong Mu Gou formation (T3t), the Lama pass group (T3lm) and the Quaternary sediments. Two long granite, porphyritic two feldspar, biotite granite, quartz diorite, etc., in this paper, we found that the content of SiO2 in rock is generally in 63.29%-79.16%, Al2O3 content varies between 10.50%-15.21%, according to the relationship between SiO2 and the constant element oxide (Al2O3, CaO, Na2O, K2O, TiO2, etc.). The samples of the long rock fall in the high potassium calc alkaline series, and the other granitoid samples fall in the high potassium calc alkaline series and the series of potassium basalite series. In the aspect of trace elements, there are similar trace elements of the primitive mantle standard distribution pattern. The rock loss of large ion stone elements Ba, Sr, P, Ti, the incompatible elements Rb, Th, U, K, Hf are rich in the rock mass. Nb*, K*, Sr* and Zr* ratio, it is concluded that the gill mountain granite base should belong to the emplacement under the tectonic setting related to the island arc zone and the collision orogeny. The overall characteristics of the rare earth elements are between 110.407-409.238, the mean value is 236.956, the LREE is between 82.798-378.822, the average value is 211.268, HREE is between 13.232-39.831, and the average value is 25.688. The average value of LREE/HREE is 8.505, the average value is 8.505, the ratio of (La/Yb) N is greater than 1, and the negative anomaly of Eu is significant (general Delta Eu1); Ce has no obvious anomaly (delta Ce 1). It indicates that the Nestle mountain rock is a high alkaline acidic rock mass and should belong to the typical crust remelting "S" granitic rock. It is also shown that the location mechanism of the broth mountain granite base is in the volcanic arc and collision tectonic environment. The isotopic age of the rock mass is 102.23 + 0.91Ma., and the deposits found in the rock and adjacent areas are mainly hydrothermal, skarn and porphyry deposits, sparrow Yamakawa Stani granites and potassium feldspar granite. The unit is related to the rare earth deposit. The K-feldspar or K2ONa2O alkali feldspar unit is related to the mineralization of W, Sn, Mo, Bi, Be. The unit composed of the alkali granite of Na2OK2O is related to Nb and Ta mineralization. The unit composed mainly of the biotite granite is related to the rare earth, W, Sn ore. The unit consisting mainly of two mica granite and W The elements composed mainly of muscovite granite are related to the mineralization of Be, Nb, Li, Ta and Rb. The types of rock alteration found in this paper include: potassium long fossilization, sodium feldspar, cloud angling, and corner rock. The possibility of a rock type deposit.
【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】：P587

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