华北克拉通1.75Ga基性岩墙群特征及其研究进展  

CHARACTERISTICS AND RESEARCH PROGRESS OF THE 1.75 GA MAFIC DYKE SWARMS IN THE NORTH CHINA CRATON:A REVIEW

作　　者：胡俊良[1] 赵太平[1] 陈伟[1] 彭澎[2] 

机构地区：[1]中国科学院广州地球化学研究所 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《大地构造与成矿学》2007年第4期457-470,共14页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(编号:40473018)资助

摘　　要：基性岩墙群是地壳伸展背景下,来自地幔的基性岩浆侵入体。华北克拉通同世界上其它克拉通一样,广泛发育前寒武纪基性岩墙群。它们在不同时代均有产生,其中1.75Ga前后的规模最大,分布范围最广,几乎遍布整个克拉通,对其进行深入研究,可以揭示华北克拉通该期构造演化过程。华北克拉通1.75Ga前后的岩墙几何形态多变,直立或近直立,走向主要为NNW向和近EW向。岩石以拉斑玄武质岩类占绝对优势(>80%),主要造岩矿物为单斜辉石和斜长石。根据岩墙走向、岩浆分异程度和岩石地球化学特征可将其分五组:低分异LT组、低分异HT组、高分异NW组、高分异EW组,以及具明显差异的高铁系列。同位素和微量元素研究显示,岩浆源区主要与富集Ⅰ型地幔(EMⅠ)、弱亏损的常规地幔(DM-PREMA)以及陆下岩石圈地幔有关。目前对华北克拉通1.75Ga基性岩墙群产出的构造环境在认识上有分歧,其中地幔柱观点和碰撞后伸展观点最为人们所关注。Mafic dyke swarms are considered to be intrusives of mantle-derived magmas formed under an extensional setting. Similar to global cratons, numerous Paleo-proterozoic mafic dyke swarms occur in the North China Craton （NCC）. The mafic dyke swarms were formed in several periods, of which the mafic dyke swarms formed at 1.75Ga are the largest in scale. These mafic dyke swarms cover an area of about 100,000km2 , occurring as vertical to sub-vertical dykes with more variable occurrence and geochemical compositions than those formed in other periods. Most （ 〉 80% ） of the dyke swarms are of tholeiitic affinity and mainly consist of clinopyroxene and plagioclase phenocrysts. Five types of the mafic dyke swarms were divided on the basis of geochemical compositions： low differentiated low-Ti （LT） group and high-Ti （HT） group, highly differentiated NW group and EW group, and high FeO, series. The parental magma of the mafic dykes is probably derived from EMI, DM-PREMA and subcontinental mantle sources. The tectonic setting under which the mafic dyke swarms formed has been greatly debated. Although the mafic dyke swarms generally formed in an extensional setting, more work is expected to constrain the types of the extensional settings, which include hypotheses such as post-collision extension, continental breakup related to plume impact and continental rifting.

关 键 词：华北克拉通 1.75Ga 基性岩墙群 地幔柱 碰撞后 

分 类 号：P581[天文地球—岩石学] P541[天文地球—地质学]