| 新疆阿尔泰巴斯铁列克钨多金属矿区花岗质岩体年代学和地球化学特征及其对成矿的启示 |
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| 引用本文： | 包长甲,柴凤梅,李永,祁冬梅,张雪冰,田猛.新疆阿尔泰巴斯铁列克钨多金属矿区花岗质岩体年代学和地球化学特征及其对成矿的启示[J].岩石学报,2021,37(3):886-910. |
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| 作者姓名： | 包长甲 柴凤梅 李永 祁冬梅 张雪冰 田猛 |
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| 作者单位： | 新疆大学新疆中亚造山带大陆动力学与成矿预测实验室, 乌鲁木齐 830046;新疆维吾尔自治区有色地质勘查局地质矿产勘查研究院, 乌鲁木齐 830000 |
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| 基金项目： | 本文受国家自然科学基金项目（41872072、42002059）和自治区自然科学基金项目（2020D01C074）联合资助. |
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| 摘 要： | 巴斯铁列克钨多金属矿床位于新疆阿尔泰造山带南缘,是近年来在区内发现的首例中型钨多金属矿床。矿体主要产于二叠纪花岗岩与上志留统-下泥盆统康布铁堡组火山-沉积岩接触带的矽卡岩中。钨矿化与矿区花岗质岩石有明显的空间关系。然而,与钨矿化有关的花岗质岩石成因尚不清楚。本文对矿区出露的与矿化关系密切的黑云母花岗岩、二长花岗岩和二云母花岗岩进行了锆石U-Pb年代学和岩石地球化学研究。3个样品的LA-ICP-MS锆石U-Pb加权平均年龄分别为282.3±3.2Ma、284.3±2.2Ma和284.8±2.3Ma,属早二叠世岩浆活动的产物,与成矿年龄一致。所有岩石具有高硅(Si O_2=73.6%~78.3%)、富碱(K_2O+Na_2O=5.15%~9.62%)富钾(K_2O/Na_2O> 1.1)、贫钙(Ca O=0.19%~0.75%)和钛(Ti O_2=0.04%~0.24%)、弱过铝-强过铝质(A/CNK=1.01~1.39)特征。这些岩石稀土元素总量(∑REE)变化较大(变化于20.3×10-6~328×10-6),但二云母花岗岩显示轻重稀土元素分异不明显((La/Yb)N=0.96~2.06)、Eu强烈负异常(δEu=0.07~0.41)的深"V"型稀土元素分布特征,黑云母花岗岩和二长花岗岩显示轻稀土略富集((La/Yb)N分别为2.8~5.5和4.8~7.4)且Eu负异常(δEu=0.33~0.39和0.34~0.63)明显的右倾型稀土元素分布特征。所有样品均显示相对富集Rb、Th、U、Pb元素和相对亏损Nb、Ti、P、Sr、Ba元素,但二云母花岗岩中W含量(4.6×10-6~9.4×10-6)相对低于黑云母花岗岩和二长花岗岩中W含量(分别为15.1×10-6~168×10-6和8.4×10-6~16.0×10-6)。所有样品的锆石具有正的高εHf(t)值(+3.8~+11)和相对年轻的亏损地幔模式年龄(Hf的tDM2为0.60~1.0Ga)。以上特征说明,这些岩石属高钾钙碱性分异I-A过渡型花岗岩。结合区域地质背景,认为这些岩体是二叠纪时期后碰撞伸展环境下两个独立岩浆事件的产物,母岩浆均来源于新生地壳熔体与幔源岩浆,经过高度分异演化后结晶形成矿区岩石。花岗质岩浆活动为巴斯铁列克钨矿床提供了成矿物质,岩浆演化过程(结晶分异与熔体-流体作用)对成矿元素有富集作用。
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| 关 键 词： | 锆石U-PB定年 HF同位素 岩石地球化学 花岗岩 巴斯铁列克 |
| 收稿时间： | 2020/11/8 0:00:00 |
| 修稿时间： | 2021/2/9 0:00:00 |
Geochronology and geochemical characteristics of granitoids in the Bastielieke tungsten polymetallic deposit in the southern margin of Altay: Implications for tungsten mineralization |
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| BAO ChangJi,CHAI FengMei,LI Yong,QI DongMei,ZHANG XueBing,TIAN Meng.Geochronology and geochemical characteristics of granitoids in the Bastielieke tungsten polymetallic deposit in the southern margin of Altay: Implications for tungsten mineralization[J].Acta Petrologica Sinica,2021,37(3):886-910. |
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| Authors: | BAO ChangJi CHAI FengMei LI Yong QI DongMei ZHANG XueBing TIAN Meng |
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| Institution: | Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University, Urumqi 830046, China;Institute of Geology and Mineral Resources Exploration, Xinjiang Nonferrous Metals Geoexploration Bureau, Urumqi 830000, China |
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| Abstract: | The medium-sized Bastielieke tungsten polymetallic deposit is a newly discovered deposit in the Kelan Basin at the southern margin of Altay Orogenic Belt.The skarn hosted the orebody which is at the outer contact zone between the granitoids and volcanic-sedimentary rocks of the Upper Silurian to Lower Devonian Kangbutiebao Formation.Two-mica granite,biotite granite and monzogranite outcrop in the Bastielieke ore district showing obvious spacial relation to the hosted ore deposits.The petrogenesis of these rocks associated with the tungsten mineralization is indefinitive.LA-ICP-MS zircon U-Pb geochronology and geochemical analysis of major and trace elements and zircon Hf isotope are performed to discuss their petrogenesis.These granites show consistent weighted mean206 Pb/238 U ages of 282.3±3.2 Ma,284.3±2.2 Ma and 284.8±2.3 Ma,respectively,which indicate that the Permian magmatic events at the southern margin of Altay is consistent to the ages of mineralization.These granitoids exhibit high Si O2 concentration(73.6%~78.3%),high total alkali(Na2 O+K2 O)(5.15%~9.62%)concentration and low Ca O(0.19%~0.75%)and Ti O2(0.04%~0.24%)concentrations.In addition,they are enriched in potassium(K2 O/Na2 O=1.08~2.06)with high A/CNK values(1.01~1.39).The total REE contents of these granites vary from 20.3×10-6 to 328×10-6 with different chondrite-normalized REE patterns.The two-mica granite is characterized by low(La/Yb)Nration(0.96~2.06)with pronounced negative Eu anomaly from0.07 to 0.41,and showing a deep V-type pattern.The biotite granite and monzogranite display enrichment of LREE with(La/Yb)N ration ranging from 2.8 to 5.5 and 4.8 to 7.4,and moderate negative Eu anomalies ranging from 0.33 to 0.39 and 0.34 to 0.63,respectively.All samples display noticeable negative anomalies of Nb,Ti,P,Sr,Ba and strong positive anomalies of Rb,Th,U and Pb.The two-mica granite has lower W concentrations varying from 4.6×10-6 to 9.4×10-6 than those in the biotite granite and monzogranite from 15.1×10-6 to 168×10-6 and 8.4×10-6 to 16.0×10-6,respectively.In addition,zirconεHf(t)values range from+3.8 to+11,two stage model ages(tDM2)ranging from 0.6 Ga to 1.0 Ga.The petrologic and geochemical data indicate that these rocks are high-K calc-alkaline and weak peraluminious to strongly peraluminous,which is similar to the geochemical behavior of the fractionated I-A type granitoids.Combined with regional geology,we suggest that they are derived from melting of the juvenile crust and mantle,and followed by subsequent crystallization fractionation in deeper magma chamber in a post-collision environment by two independent magmatic events.These granites provide key ore components for the formation of Bastielieke tungsten polymetallic deposit and preconcentrate tungsten by crystallization fractionation and melts-fluid exsolution. |
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| Keywords: | Zircon U-Pb dating Hf isotope Geochemistry Granitoids Bastielieke |
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