Petrology, geochemistry and geochronology of the intermediate to mafic dykes in northern Xinjiang since Late Paleozoic

新疆北部中基性岩脉K-Ar表观年龄为187～271Ma,岩性以辉长、辉绿岩以及闪长、闪长玢岩为主,属于亚碱性系列.主量元素、稀土元素以及微量元素分析表明,中基性岩脉经历了源区地壳物质的混合以及侵位过程中的分离结晶作用,并在区域分布特点上受部分熔融程度的影响,而且由于结晶分异和部分熔融的不同,还出现了中基性岩脉系列的成分变异.排除上述岩浆作用的干扰,有证据显示岩脉起源于亏损地幔,由于Nd同位素模式年龄tDM集中在363～769Ma,反映源区是一个古生代时期的新生岩石圈地幔,该地幔源区属于大洋岩石圈地幔.新疆北部广泛出露的中基性岩脉在时间和空间上具有多样性,但是在产状、岩性组合和同位素特征上具有相似的特点,指示研究区在古生代以来具有一个相对统一和完整的源区,推测这个源区与北疆地区古生代以来长期存在的残余洋盆及其相关岩石圈有关.The K-Ar ages of the intermediate to mafic dykes in northern Xinjiang are in the range of 187 similar to 271 Ma. These dykes are principally composed of gabbro, diabase, diorite and dioritic porphytite, belonging to the subalkaline series. Analysis of major elements, REE and trace elements suggest provenance contamination as well as fractional crystallization during emplacement, and the regional distribution characteristics of these dykes are controlled by the extent of partial melting. The composition variations are also produced due to difference of the fractional crystallization and partial melting. Excluding the influence of magmatism above, there is evidence showing that the dykes are originated from depleted mantle. The Nd isotopic model ages (t(DM)) are concentrated in 363 Ma and 769Ma, which implies that the source region is a Paleozoic fresh lithospheric mantle, and this mantle reservoir belongs to oceanic lithosphere mantle. These intermediate to mafic dykes widely exposed in northern Xinjiang have similar characteristics of occurrence, lithologic association and isotope in spite of diverse temporal and special features, which indicates that a relatively uniform and integrated source region has existed in northern Xinjiang since Paleozoic. It is likely to infer that this source region is related with the long lasting residual oceanic basin and the related lithosphere since Paleozoic in north Xinjiang.国家重点基础研究发展计划(973计划); 国家重点基础研究发展计划(973计划); 国家自然科学基金http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000259628700005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)255977-9962