全文快速搜索:          
引用本文:刘阁,舍建忠,杨文龙,王庆军,贾健,邸晓辰. 西准噶尔巴音达拉地区卡拉岗组火山岩锆石U-Pb年代学、地球化学及其地质意义[J]. 中国地质, 2018, 45(6): 1241-1250.
LIU Ge,SHE Jianzhong,YANG Wenlong,WANG Qinjun,JIA Jian,DI Xiaochen. Zircon U-Pb chronology and geochemistry of the Kalagang Formation volcanic rocks in Bayindala area,West Junggar, and their geological significance[J]. Geology in China, 2018, 45(6): 1241-1250(in Chinese with English abstract).
【打印本页】   【HTML】   【下载PDF全文】   查看/发表评论  下载PDF阅读器  关闭
←前一篇|后一篇→ 过刊浏览    高级检索
本文已被:浏览 520次   下载 415 本文二维码信息
码上扫一扫!
分享到: 微信 更多
西准噶尔巴音达拉地区卡拉岗组火山岩锆石U-Pb年代学、地球化学及其地质意义
刘阁1, 舍建忠1, 杨文龙2, 王庆军1, 贾健1, 邸晓辰1
1.新疆地质调查院, 新疆 乌鲁木齐 830000;2.核工业二一六大队, 新疆 乌鲁木齐 830011
摘要:
西准噶尔巴音达拉地区发育一套酸性火山岩,被称为卡拉岗组,岩石组合以流纹岩、英安岩、流纹质熔结凝灰岩等酸性火山岩为主。本文对卡拉岗组火山岩进行高精度锆石LA-ICP-MS U-Pb测年,获得英安岩和流纹岩的加权平均206Pb/238U年龄分别为(294.4±1.3)Ma(n=9,MSWD=0.8)和(298.4±2.5)Ma(n=9,MSWD=3.4),其形成于早二叠世。岩石地球化学特征表明,卡拉岗组火山岩岩具有高硅(66.69%~75.21%),富碱(Na2O+K2O:6.98%~8.35%),低MgO(0.18%~1.32%),贫钙(0.24%~2.49%)的特征,均属过铝质(A/CNK:1.14~1.33)及高钾钙碱性系列。微量元素数据显示,稀土总量为∑REE为83.82×10-6~197.61×10-6,(La/Yb)N=3.15~12.50,轻、重稀土元素分馏比较明显,轻稀土元素(LREE)较为富集,重稀土元素分布相对平坦,球粒陨石标准化配分模式为右倾型。微量元素富集大离子亲石元素(LILE)Rb、Th、U、K,并亏损高场强元素(HFSE)Nb、Ta、P、Ti。综合最新区域资料及本文研究成果,文章认为研究区早二叠世卡拉岗组火山岩岩浆来源于壳源物质不同程度的部分熔融,残留相中有少量斜长石和角闪石,为后碰撞伸展阶段的产物。
关键词:  卡拉岗组  火山岩  岩石成因  后碰撞  西准噶尔
DOI:10.12029/gc20180613
分类号:P597+.3;P588.14
基金项目:中国地质调查局"新疆区域地质调查片区总结与服务产品开发"项目(DD20160345-04)资助。
Zircon U-Pb chronology and geochemistry of the Kalagang Formation volcanic rocks in Bayindala area,West Junggar, and their geological significance
LIU Ge1, SHE Jianzhong1, YANG Wenlong2, WANG Qinjun1, JIA Jian1, DI Xiaochen1
1.Geological Research Academy of Xinjiang, Urumqi 830000, Xinjiang, China;2.No. 216 Geological Party of CNNC, Urumqi 830011, Xinjiang, China
Abstract:
Silicic volcanic rocks are developed in Bayindala area of West Junggar. The Kalagang Formation volcanic rocks are mainly composed of rhyolite, dacite, rhyolitic tuff and ignimbrite. This paper reports the results of high-precision zircon LA-ICPMS U-Pb dating of the Kalagang Formation volcanic rocks, which yielded weighted mean 206Pb/238U ages of(294.4±1.3) Ma (n=9, MSWD=0.8, dacite) and(298.4±2.5) Ma (n=9, MSWD=3.4, rhyolite), corresponding to the Early Permian. Petrogeochemical analyses suggest that the Kalagang Formation volcanic rocks are characterized by high silica (SiO2:66.69%-75.21%) and alkali (Na2O + K2O:6.98%-8.35%), and low magnesium and calcium (MgO 0.18%-1.32%, CaO 0.24%-2.49%). They belong to peraluminous (A/CNK:1.14-1.33) and high-K calc-alkaline series. The rocks are poor in rare earth elements with ∑REE being 83.82×10-6-197.61×10-6, enriched in LREE[(La/Yb)N=3.15-12.50] and LILEs (Rb,Th,U,K) and depleted in HFSE, especially Nb, Ta, P and Ti. In combination with previous studies, the authors hold that the Kalagang Formation volcanic rocks in a postcollisional extensional setting were formed by varying degrees of crust partial melting and the residua had a little plagioclase and hornblende.
Key words:  Kalagang Formation  volcanic rock  petrogenesis  post-collision  West Junggar