| 东天山觉罗塔格构造带石炭纪弧后盆地:来自基性火山岩的证据 |
| |
| 引用本文： | 罗婷,陈继平,廖群安,王国灿,张雄华,张随安,康琴琴.东天山觉罗塔格构造带石炭纪弧后盆地:来自基性火山岩的证据[J].地球科学,2020,45(1):194-210. |
| |
| 作者姓名： | 罗婷 陈继平 廖群安 王国灿 张雄华 张随安 康琴琴 |
| |
| 作者单位： | 1.陕西省地质调查实验中心, 陕西西安 710054 |
| |
| 基金项目： | 中国地质调查局区域地质调查项目12120114042801中国地质调查局区域地质调查项目1212011120503中国地质调查局区域地质调查项目1212011120509中国地质调查局区域地质调查项目DD20160006 |
| |
| 摘 要： | 中亚造山带西南缘东天山觉罗塔格造山带广泛发育石炭纪火山岩，这些石炭纪火山岩的成因和构造历史一直是该区域地质问题争论的焦点.通过对东天山觉罗塔格造山带石炭纪基性火山岩详细的岩石学、地球化学、锆石U-Pb年代学和Sr-Nd同位素研究，获得了如下认识:（1）东天山觉罗塔格造山带石炭纪基性火山岩分为两期爆发，早期爆发时间为336 Ma，晚期爆发时间为320 Ma.早期336 Ma基性火山岩由玄武岩、玄武安山岩及同成分的火山碎屑岩组成，显示出弧火山岩属性；晚期320 Ma基性火山岩主要由玄武岩和玄武安山岩组成，包括Ⅰ型火山岩和Ⅱ型火山岩，Ⅰ型显示出大洋中脊玄武岩属性，Ⅱ型显示出弧玄武岩特征.（2）石炭纪基性火山岩中发现的大量捕获锆石（371~3 106 Ma）年龄谱系与中天山地块显示为相似的特征，表明它们在石炭纪之前可能同属一个板块，也指示早古生代地壳可能参与了成岩过程.（3）该区域石炭纪火山岩与现今存在的Okinawa Trough和Mariana Trough弧后盆地玄武岩（BABB）很相似，从弧玄武岩向洋中脊玄武岩的演变，反映了石炭纪中天山北部弧后盆地的发展.因此推断早石炭世火山岩为弧后盆地初始裂开阶段的产物，而晚石炭世火山岩为弧后盆地弧后扩张阶段的产物.早石炭世晚期的初始裂开和晚石炭世早期的弧后扩张表明天山洋的俯冲最终结束于晚石炭世末期，包括主大洋和弧后盆地最终关闭，而最终关闭的位置很可能位于中天山以南.
|
| 关 键 词： | 火山岩 石炭纪 岩石成因 弧后盆地 东天山 岩石学 |
| 收稿时间： | 2018-09-04 |
A Back-Arc Basin in Eastern Tianshan,Central Asia: Evidence from Geochronology and Geochemistry of Carboniferous Basalts |
| |
| Abstract: | Carboniferous volcanic rocks are widely distributed in the Jueluotage belt of eastern Tianshan, located in the southern Central Asian Orogenic Belt. The petrogenesis and tectonic history of this region have long been a matter of debate. Data on major and trace elements and Sr-Nd isotopes of whole rocks, and in-situ U-Pb age of zircons are reported for Carboniferous volcanic rocks in the Juluotage area in this paper. The main results are obtained as follows:(1) These volcanic rocks erupted in two episodes, with zircon U-Pb ages of ca. 336 Ma and ca. 320 Ma respectively. The ca. 336 Ma volcanic rocks are dominated by arc-like igneous rocks. They show enrichment of light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), and depletion of high field-strength elements (HFSEs) according to the N-MORB-normalized and chondrite-normalized diagrams. However, the ca. 320 Ma volcanic rocks mainly consist of MORB-like igneous rocks that show nearly flat REE patterns. They are also slightly enriched in LILEs and LREEs according to the N-MORB-normalized and chondrite-normalized diagrams. (2) The inherited zircon ages of volcanic rocks from the Jueluotage belt show similar trends and features to those of the Central Tianshan Block, suggesting they shared the same basement, at least before the Early Carboniferous. (3) These Carboniferous volcanic rocks are geochemically similar to the back-arc basin basalt (BABB) from the Mariana and Okinawa troughs. The evolution from arc-like volcanic rocks to MORB-like volcanic rocks reflects the development of the back-arc basin in the northern Central Tianshan Block during the Carboniferous. The subduction of the Tianshan Ocean ended at the end of the Late Carboniferous period. The final closure of the main ocean and back-arc basins is likely to be south of the Central Tianshan mountain. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
| 点击此处可从《地球科学》下载免费的PDF全文 |
