摘要
中国阿尔泰广泛发育的花岗质岩石已获得大量研究,但是其东南缘研究薄弱,制约了对整个阿尔泰造山带构造岩浆演化的认识。本文新获得阿尔泰东南缘四个花岗质岩体(昆格依特、库吉尔特、布铁乌及卡拉特玉别)锆石U-Pb年龄,分别为382±4Ma、381±4Ma、385±5Ma和363±6Ma。岩石学、地球化学特征等显示这些花岗质岩石具有高钾钙碱性、准铝质—弱过铝质的I型特点,全岩εNd(t)值为-2.42^-0.53,Nd模式年龄tDM为1.6~1.3Ga;锆石εHf(t)值为-3.44^+13.26,绝大多数为正值,锆石Hf二阶段模式年龄tDM-2为2.5~0.6Ga,表明源区物质组成复杂,有较多的新生幔源物质参与花岗质岩石的形成,并含有古老地壳成分。综合已有年龄分析显示,中国阿尔泰花岗质岩石的形成时代可分为480~440Ma(峰期460Ma)、420~390Ma(峰期400Ma)、390~370Ma(峰期380Ma)、370~360Ma(峰期365Ma)、360~350Ma。处于岩浆发育峰期的早泥盆世(420~390Ma)多为准铝-过铝质的钙碱性系列;中晚泥盆世(390~360Ma)多为准铝—弱过铝质的高钾钙碱性系列;370~360Ma为高钾钙碱性系列。该地区363Ma的高钾钙碱性花岗质岩石的确定,为进一步厘定整个阿尔泰泥盆纪花岗质岩浆由钙碱性(480~390Ma),到高钾钙碱性(390~360Ma),再到354Ma的布尔根碱性花岗岩的演变特点提供了新的证据,进一步揭示阿尔泰造山带该时期由俯冲增生演变到碰撞及后碰撞的演化过程。
Many researches on the granitoids in most area of the Chinese Altai have been carried out, but retracing the entire tectono-magmatic evolutionary history of the Chinese Altai orogen is still being restricted due to the lack of understanding on the southeastern Altai. This study is based on four samples of granitic plutons （Kungeyite, Kujierte, Butiewu and Kalateyubie）, zircon U-Pb （LA-ICP-MS） dating yields the ages of 382 ＋4Ma, 381 ±4Ma, 385 4-5Ma and 363± 6Ma, respectively. These granitic rocks belong to high-K calc-alkaline and metaluminous-weakly peraluminous series of type I, depending on their petrological and geochemical characteristic. They have negative whole rock εNa （t） values of -2. 42-0.53 with Nd model ages tDM Of 1. 6 - 1. 3Ga and zircon εHf （t） values of - 3.43 - ＋ 12.89 （mostly positive）, with Hf model ages tDM-2 Of 2. 5-0. 6Ga, suggesting complex sources. These data indicates mantle-derived substances involved during the process of generation of granitoids as well as ancient crustal compositions. The Devonian granitic rocks in the Chinese Altai can be classified as Early Devonian （420- 390Ma） and Middle-Late Devonian （390 - 360Ma）; the former is mostly calc-alkaline series of metaluminous-peraluminous and the latter is high-K calc-alkaline series of metaluminous-weakly peraluminous. It provides new evidence for the features of evolvement of the Early-Middle Devonian granitoids from calc-alkaline series （480-390Ma） to high-K calc-alkaline series （390-360Ma）, then to alkine granite （354Ma）, because of the certainty of high-K calc-alkaline granitic rock （363Ma） in this area. This evolvement further confirmed the evolution process of the Chinese Altai are consistent with tectonic settings from subduction to collision and then to post-collision extentional environment. Combined with the analysis of isotope and regional geological data, we conclude that the Middle-Late Devonian granitoids in the southeastern Chinese altai are active continental arc environment in the background of subduction. The Late Devonian granitoids have the characteristics of collision, followed by the Early Carboniferous post-collision alkaline granite.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2017年第1期55-79,共25页
Acta Geologica Sinica
基金
NSFC-新疆联合基金重点支持项目(U1403291)
中国地质调查局项目(编号:12120113094000
1212010811033
12120113096500
1212010611803)联合资助
关键词
花岗质岩石
锆石年龄
岩浆演化
同位素
泥盆纪
阿尔泰
Granitic rocks
LA-ICP-MS zircon U-Pb ages
Magmatic evolution
Isotopegeochemistry
Devonian
Altai
作者简介
宋鹏，男，1988年生，博士研究生，花岗岩与构造地质学，Email：songpengyx@foxmail．com。
通讯作者：王涛，男，1959年生，博士生导师，研究员，从事花岗岩及构造研究，Email：taowang@cags．ac．cn。
