【作者】 陈超；

【导师】 吕新彪；

【作者基本信息】 中国地质大学 ， 矿床普查与勘探， 2010， 硕士

【摘要】 中天山地块位于天山山脉中部,一般认为是准噶尔与塔里木板块之间的一个微陆块,其西宽东窄,在库米什以东地区尖灭。南天山洋盆在晚古生代开始向北俯冲于中天山地块之下,致使中天山南缘在晚古生代形成一系列与俯冲-碰撞有关的火山岩及侵入岩,并控制了本区不同类型矿床的产出。忠宝钨矿即产于中天山地块南缘北西西向花岗岩带上。本文在野外地质工作及收集前人资料的基础上,以库米什地区区域地质背景、构造演化、忠宝岩体的成因研究为基础,详细研究了忠宝钨矿的矿床地质特征、矿体地质特征及矿床成因,并总结了矿床的成矿模式,最后结合矿区外围相关化探及遥感异常分析,对库米什地区钨矿化远景作出推断。库米什地区演化经弧后扩张-俯冲-碰撞-后期拉张回返构成一个典型的威尔逊旋回,后期受走滑构造作用形成拉分盆地。其中南天山洋盆向北俯冲-碰撞阶段为本区的主要成矿阶段,并控制了区内铜铅锌多金属矿床、钨矿等矿床的形成。忠宝二云母二长花岗岩与钨矿化关系密切,锆石U-Pb年代学研究获得其侵入年龄为298±3.2Ma,属晚石炭世。地球化学特征表明忠宝二云母二长花岗岩为具有中等-高的分异演化程度的高钾钙碱性过铝质花岗岩,为形成于同碰撞环境的壳源重熔S型花岗岩,源岩为中天山前寒武系基底。岩体钨含量高,为忠宝钨矿的主要金属成矿物质来源。野外观察及室内研究表明,忠宝钨矿为矽卡岩型白钨矿矿床,叠加了云英岩矿化及后期石英脉矿化。矿体产出于库米什背斜东部倾伏端,背斜转折端及两翼形成许多次级小褶皱,相邻岩层相对滑动致使褶皱的枢纽及两翼部分常形成层状、似层状、马鞍状剥离空洞,有利于岩体进入围岩进行矽卡岩交代。背斜南翼地层受NE向断裂破坏从而为岩浆侵入提供了通道及侵入空间,后期近SN向断裂构造多为对矿体的后期改造,忠宝钨矿矿体形态特征即受到上述多重控矿因素的影响。矿石类型主要为石榴透辉绿帘石矽卡岩型、阳起透辉符山石矽卡岩型、云英岩型、矽卡岩化大理岩型等,多为半自型粒状结构、纤状变晶结构、鳞片粒状变晶结构,块状、条带状构造。主要矿石矿物为白钨矿,呈浸染状赋存于各类矿石中,其次为少量锡石及黄铁矿。脉石矿物为透辉石、符山石、绿帘石、石榴石、硅灰石、透闪石、石英、萤石、白云母、黑云母、方解石等。成矿作用按先后顺序可分为矽卡岩期及云英岩-石英白钨矿期,其中矽卡岩期可分为早期矽卡岩阶段和晚期矽卡岩阶段,云英岩-石英白钨矿期可分为云英岩阶段和石英-白钨矿阶段。后三个阶段为主成矿阶段。石英碳酸盐阶段已无钨矿化形成。岩体及围岩的钨含量研究表明钨主要来源于成矿花岗岩体,推断中天山地块前寒武系基底为钨的有利含矿建造,而下泥盆统地层可作为贫的矿源层提供部分物质来源。石英氢氧同位素研究表明成矿流体来源为岩浆水,与忠宝岩体关系密切。白钨矿氧同位素研究显示其具有矽卡岩型白钨矿的氧同位素特征(180富集)。通过对矿区白钨矿、透辉石、石英、萤石、方解石的流体包裹体测试分析,对矿床的成矿物理化学条件获得以下认识：(1)成矿系统流体温度在140℃-440℃之间,白钨矿主矿化阶段温度为250～360℃,平均温度为308.78℃,属高-中温环境。成矿温度从早期矽卡岩阶段-晚期矽卡岩阶段-石英～白钨矿阶段-石英～碳酸盐阶段依次降低,其中晚期矽卡岩阶段和石英-白钨矿阶段为主要成矿阶段。(2)成矿系统流体盐度在6%-22%之间,其中白钨矿包裹体盐度在12%～15%之间,平均盐度为13.41%,为中高盐度环境。成矿流体盐度在矿化过程中亦呈逐渐下降趋势。(3)成矿系统流体密度在0.792 g／cm3～0.967 g／cm3之间,其中白钨矿包裹体中流体密度为0.844g／cm3。受挥发分含量及温度影响,成矿流体密度在矿化过程中亦呈逐渐增大的趋势。(4)成矿压力在149～461×105Pa之间,其中形成白钨矿的平均压力为353×105Pa,从早期成矿阶段到晚期成矿阶段成矿压力呈递减趋势,反映了成矿流体向浅部运移并在断裂、破碎带等有利构造部位发生矿化的过程。(5)不同矿物形成深度在1.1km-4.5 km之间,其中白钨矿形成深度2.7-4km,矿化形成于中等深度。通过以上对忠宝钨矿的矿石类型、围岩蚀变特征、含矿岩体岩石化学特征、氢氧同位素及流体包裹体研究,表明忠宝钨矿为典型的矽卡岩型白钨矿矿床,形成于晚石炭世南天山洋向中天山微板块俯冲闭合过程形成的同碰撞花岗岩带,成矿物质来源于深部地壳重熔,成矿流体为深部岩浆水,矿床形成于中-高温度(250～360℃)、高盐度(12%-15%),中等深度(2.7～4k)和较高的压力环境(353×105Pa)。多光谱、高光谱遥感异常,地球化学异常显示,库米什地区钨的异常具有明显的沿北西西方向分布于中天山地块南缘及地块内部的特征,该异常特征为晚古生代末期南天山洋向中天山地块俯冲形成俯冲-碰撞型富钨花岗岩的结果,受区域断裂控制而呈北西西向。综合分析各种矿致异常及其地质解释,本文认为中天山地块南缘碰撞花岗岩与异常吻合较好的地区具有良好的钨矿找矿前景,中天山地块内部及塔里木北缘亦是钨矿的有利远景区。更多还原

【Abstract】 Middle tianshan block, a microcontinent between junggar and tarim block, is located in the middle of tianshan belt and pinches out at the east of Kumishi area. The oceanic crust of south tianshan subducted norwards under the middle tianshan block,which lead to the formation of series of volcanic and intrusive rocks related to the subduction and collision at the south of middle tianshan block in the late Paleozoic and control the formation of different types of deposits. Zhongbao tungsten deposit is located in the NWW-trending granite belt at the south of middle tianshan block.On the basis of geological works in the field and previous data,this paper firstly discussed the regional geological setting, tectonic evolution of Kumishi area and the genesis of Zhongbao granite and detailedly studied the geological characteristics of deposit and orebody and its genesis and then summarized the metallogenic model of Zhongbao tungsten deposit.At last,we gave the conclusion about the prospect of tungsten mineralization in Kumishi area combining with the analyse of geochemical exploration and remote sensing.The tectonic evolution of Kumishi area successively experience back-arc extension-subdction-collision-post collision processes which compose a typical wilson cycle and later a pull-apart basin was formed by strike-slip tectonic processes.The stage of subdction and collision between the oceanic crust of south tianshan and middle tianshan block is the main mineralization stage which control the formation of Cu-Pb-Zn polymetallic deposits and W-Sn deposites in this area.Zhongbao two-mica monzogranite is closely related to the tungsten mineralization.U-Pb Zircon dating for the Zhongbao granite yield a weighted mean age of 298±3.5 Ma, belonging to late-devonian carboniferous. geochemical characteristics indicate that Zhongbao granite is potassium-rich calc-alkaline and peraluminous granite which experienced a medium-high degree differential evolution process.lt belongs to Crustal melting S-type granite which formed in the collision setting and its source rock is Precambrian basement of middle tianshan block.The rock body is tungsten-rich and provides main metal source for Zhongbao tungsten deposit.Field observations and studies show that Zhongbao tungsten deposit belongs to skarn-type scheelite deposit with the superposition of greisen mineralization and late quartz vein mineralization. The orebodies are located in the east plunging crown of Kumishi anticline.As the Turn end and the two wings of anticline always form a number of secondary folds, The relative sliding of adjacent strata usually leads to the layered, like layered, saddle-shaped peeling space at the fold hinge and two wings which is advantageous to skarn metasomatism between the granite and wall rock.The strata at the south wing which is damaged by the NE-trending fracture provide the channel and intrusive space for the magma and the later SN-trending fracture mostly cause the later transformation of the ore body. The morphological characteristics of zhongbao tungsten deposit ore body are controlled by the affects of the multiple ore-controlling factors.Ore types in the district are mainly Gt-Di-Ep skarn type, Act-Di-Ves skarn type, greisen type, and skarnised marble tpye. Hypidiomorphic granular texture, nematoblastic texture, and lepido-granular blastic texture are developed and the ores are massive or banded. The ore mineral is sheelite disseminated in the all ores types and minor cassiterite and pyrite. Gangue minerals are mainly diopside, idocrase, epidote, garnet, wollastonite, tremolite, quartz, fluorite, muscovite, biotite and calcite.Mineralization is divided into skarn period and greisen-quartz scheelite period in Chronol-ogical order, in which the skarn period is divided into early stage and late stage, and the greisen-quartz scheelite period is divided into greisen stage and quartz scheelite stage. The late three stages is the main mineralization stage. Quartz carbonate stage doesn’t form the Tungsten ore. The study of the content of tungsten in rock mass and country rock indicates that tungsten is mainly originated from the mineralization granitic intrusion, infering that precambrian system basement from middle Tianshan land mass is a beneficial ore bearing formation for tungsten, and stratum from Lower Devonian is to provide partial material source as a poor source bed. Oxygen and hydrogen isotope studies from quartz make clear that ore-forming fluid devided from the magmatic water, closely related to the Zhongbao rock mass. Hydrogen isotope study from scheelite shows that belongs to skarn type.After the study of the fluid inclusions in the sheelite, diopside, quartz, fluorite, and calcite, we obtained the following knowledge of ore-forming P-T conditions.(1)All tested data show that the homogeneous tempetature is between 140-440℃, while the main mineralizing stage of sheelite happened between 250-360℃with mean temperature of 309℃. It is belonging to the scope of high to medium temperature. Ore-forming temperature gradually descending from early skarn stage, late skarn stage, quartz-sheelite stage to quartz-carbonaite stage, among which the late skarn stage and the quartz-sheelite stage are the main ore-forming stage. (2) The salinity of the ore-forming fluid is between 6% to 22%. The salinity of the fluid inclusions in sheelite is between 12% to 15% with the mean salinity of 13.41%. It is belonging to middle to high salilinty settings. During the mineralization, it gradully descending.(3) The desity of the ore-forming fluid is between 0.792g/cm3 and 0.967g/cm3. The desity of the fluid captured in sheelite is 0.844g/cm3. Influenced by the volatiles and temperature, the fluid desity increases during the mineralizing process.(4) The ore-forming pressure is between 146 and 461 bar. The sheelite is formed at 353 bar. The depressing of ore-forming pressure from early stage to late stage reflects the movement of ore-forming fluid to shallow depth and deposit the minerals in the fractures and crused zones.(5) The minerals are formed at the depth of 1.1-4.5 km. Sheelite is formed at the depth of 2.7-4km, which is moderate.With the study of the ore types, wall rock alteration, geochemistry of ore-bearing pluton, fluid inclusions and H-O isotope of the fluid at Zongbao Tungsten deposit, we believe it is a typical skarn-type sheelite deposit which is formed during the subduction to the Middle Tian and close of South Tianshan ocean. The deposit is genetical associated with the co-collisional granite. The ore substances are derived from the melting of deep crust. The ore-forming fluid is deep drived magmatic water. P-T condition of the deposit is obtained with high to middle temperature (250-360℃), high salinity (12%-15%), middle depth (2.7-4km) and relatively high pressure (353 bar).Multispectral, hyperspectral remote sense and geochemical anomaly show that tungsten anomaly in Kumux region is characterized by apparently distributing in the southern edge of middle Tianshan land mass and inner of that along the NWW direction, which resulted from the subduction from south Tianshan ocean to middle Tianshan land mass forming Subduction-collision type tungsten-rich granite in the late Paleozoic telophase, being NWW direction under the control of regional fault. Comprehensive analyzing of various anomalies related to mineraliz- ation and the geological interpretation, this article considered Collision granites from the southern edge of middle Tianshan land mass and the religion in agreement with the anomalies has bright future for tungsten ore propects, inner of middle Tianshan land mass and the north edge of Tarim is also the favorable direction for the tungsten ore.更多还原