| 新疆中天山北缘望峰地区花岗岩的地球化学、锆石U-Pb年代学及Hf同位素组成研究 |
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| 引用本文： | 杨猛,王居里,王建其,党飞鹏.新疆中天山北缘望峰地区花岗岩的地球化学、锆石U-Pb年代学及Hf同位素组成研究[J].岩石学报,2012,28(7):2121-2131. |
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| 作者姓名： | 杨猛 王居里 王建其 党飞鹏 |
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| 作者单位： | 大陆动力学国家重点实验室,西北大学地质学系,西安710069 |
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| 基金项目： | 本文受国家科技支撑计划项目(2006BAB07B04-05)和西北大学研究生创新基金项目(自主创新型)(10YZZ23)联合资助 |
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| 摘 要： | 新疆中天山北缘望峰地区花岗岩的岩石学、地球化学及锆石U-Pb-Hf同位素研究表明:(1)望峰地区花岗岩岩石类型主要为二云母二长花岗岩和黑云母二长花岗岩,岩体高SiO2、Al2O3,中等富碱且相对富钾,A/CNK≥1.1,稀土含量中等(∑REE=162.6×10-6～211.8×10-6),轻重稀土分馏明显且富集轻稀土,具中等Eu负异常(δEu=0.42～0.49),相对富集LILE和LREE,亏损Ba、Sr、P、Ti、Nb、Ta、HREE等,属高钾钙碱性过铝质S型花岗岩; (2)锆石LA-ICP-MS U-Pb定年获得岩浆结晶年龄为439.9±2.2Ma,成岩时代为早志留世; (3)锆石Hf同位素组成较均一,εHf(t)=-5.0～-1.3,平均-2.72,二阶段模式年龄tDM2变化范围在1294～1482Ma之间,岩浆主要来源于中元古代中期地壳结晶基底岩系的部分熔融,源岩为经历过风化旋回、成熟度较低的硬砂岩,形成于中天山北缘早古生代碰撞造山期同碰撞环境。
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| 关 键 词： | S型花岗岩 早志留世 源岩组成 同碰撞造山 新疆望峰地区 |
| 收稿时间： | 2011/10/8 0:00:00 |
| 修稿时间： | 2012/3/22 0:00:00 |
Studies on geochemistry,zircon U-Pb geochronology and Hf isotopes of granite in Wangfeng area at the northern margin of Middle Tianshan,Xinjiang |
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| YANG Meng,WANG JuLi,WANG JianQi and DANG FeiPeng.Studies on geochemistry,zircon U-Pb geochronology and Hf isotopes of granite in Wangfeng area at the northern margin of Middle Tianshan,Xinjiang[J].Acta Petrologica Sinica,2012,28(7):2121-2131. |
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| Authors: | YANG Meng WANG JuLi WANG JianQi and DANG FeiPeng |
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| Institution: | State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China |
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| Abstract: | Rock samples in Wangfeng area consisting of two-mica monzonitic granite and biotite monzonitic granite locate in the northern margin of Middle Tianshan in Xinjiang,exhibiting as the direct gold-bearing country rocks,which synthetically display characteristics of peraluminous S-type granite or MPG belonging to high-K calcalkaline series:Allitic mineral assemblages of granitic rocks with medium-fine grained granitic texture and weakly gneissic structure comprise primary muscovite and biotite.Geochemically,Wangfeng granite is characterized by high SiO2,Al2O3 and ALK with K2O/Na2O ratios changing from 1.07 to 1.25 and 1.15 on average,A/CNK ratios range from 1.10 to 1.12 and 1.11 on average.Granite samples are rich in LREE and LILE(K,Rb,Th,U etc.),infertile in HREE and Ba,Sr,P,Ti,Nb,Ta etc.,coupling with moderate Eu negative anomaly(δEu=0.42～0.49),which are in relation to magmatic fractionation.Wangfeng granite intruded at 439.9±2.2Ma based on the dating results of zircon U-Pb geochronology.Zircon Lu-Hf isotopic compositions indicate that εHf(t)=-5.0～-1.3 with an average of-2.72,two-stage model ages(tDM2)range from 1294Ma to1482Ma,which yields Wangfeng granite derived from partial melting of Mid-Mesoproterozoic crystallized basements formed during the process of metamorphism of greywacke combining with the plotting results of experimental petrology.In terms of both previous research results on regional tectonic setting and tectonic discrimination diagrams,Wangfeng granite formed at the syn-collisional stage of Caledonian Orogeny,there is a quite significant conclusion that Middle Tianshan may be compound,which is composed of orogenic belts with distinct inner frameworks. |
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| Keywords: | S-type granite Early Silurian Source rock Syn-collisional orogeny Wangfeng Xinjiang |
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