鄂尔多斯盆地晚古生代沉积岩源区构造背景及物源分析
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国家重点基础研究发展计划(973计划)


Tectonic setting and provenance analysis of Late Palaeozoic sedimentary rocks in Ordos Basin
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    摘要:

    鄂尔多斯盆地周缘物源均来自上地壳,以长英质岩石为主,主要为太古界、元古界的各类变火山-沉积岩组成的古老变质岩系,同时具有一定量的花岗岩和碱性玄武岩的混合,但物源成分及南北源区构造背景有所差异。在常量元素及稀土元素组成上,盆地南北物源区的沉积岩在地区及层位之间存在差异,且该变化符合大洋岛弧→大陆岛弧→活动大陆边缘→被动大陆边缘常量元素、稀土元素以及负Eu 异常的变化趋势。常量元素变化分析表明盆地北部物源主要来自板块俯冲碰撞地带,与被动大陆边缘环境和活动大陆边缘环境相关,少数为与活动大陆边缘相关的岛弧构造环境有关,到晚古生代中晚期才逐渐与被动大陆边缘环境和活动大陆边缘环境相关。稀土元素对比分析表明,盆地北部物源与太古代、元古代的花岗片麻岩、闪长片麻岩、二长花岗岩、变余岩屑砂岩及千枚岩具有亲源性;而盆地南部早-中二叠世长期受被动大陆边缘物源影响,具有高SiO2,低Na2O的特征,这与太古代-元古代的太华群、秦岭群、宽坪群等岩系的高SiO2含量,K2O/Na2O>1 的特征一致,到晚古生代后期,逐渐与活动大陆边缘物源相关。北秦岭晚古生代山间盆地具有快速混杂堆积的沉积特点,属于盆地外缘,并与鄂尔多斯盆地呈连续过渡的状况,物源上具有继承关系;盆地晚古生代沉积岩中Gd含量及ωn(Gd)/ωn(Yb)比值具有随时间迁移的特征,分析表明北部物源区在太原期处于构造快速活动期,而南部物源从山西期才开始进入快速活动期,这与区域构造演化背景一致,即北部物源区抬升要早于南部。

    Abstract:

    The provenance of Ordos Basin surrounding region is all come from the upper crust, mainly is felsic rocks which is ancient metamorphic rock series composed by metamorphotic volcanic rock and sedimentary rock of Archaeozoic and Proterozoic, and alse has a quantitative of mixed rock of granite and alkaline basalt, but provenance composition and tectonic setting of south and north provenance area has difference. In the composition of major elements and REE, some differences exist in area and stratum, and the changes of major element, REE and Eu anomaly are accorded with the variation trend from oceanic island arc, continental island arc, and active continental margin to passive continental margin. Based on analysis of major element, the north provenance is thought as coming from plate subduction zones that mainly is tectonic setting of active continental margin and passive continental margin, minority pertain to the island arc of passive continental margin, and develop gradually to tectonic setting of active continental margin and passive continental margin until middle-advanced Late Palaeozoic. Based on comparative analysis, the north provenance is thought as coming from Archaeozoic and Proterozoic metamorphotic rocks, such as granitic gneiss, diorite gneiss, adamellite, metamorphotic litharenite, phyllite, etc. In the southern basin, the provenance having high SiO2 content, low Na2O features,is affected by passive continental margin, which is similar or consistent features of Archean-Proterozoic rock series, with high SiO2 content, K2O/Na2O>1, such as Taihua Group, Qinling Group, Guanping Group etc., but until later stage of late Paleozoic, the related provenance is gradually affected by active continental margin. In Beiqinling intermontane basins, as the outer margin of Ordos Basin having continuous transitional relationship between them, which has the certain sedimentary characteristics of rapid accumulation mélanges. Late Paleozoic, in Ordos basin, the Gd content and ωn (Gd)/ωn (Yb) ratios of the sedimentary rocks has migration characteristics with time, analysis showed that the northern source area in Taiyuan period is in rapid tectonic activity period, while the southern source area in Shanxi period is fast active period, which is consistent with the regional tectonic evolution, the uplift of the northern source area earlier the south.

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陈全红,李文厚,胡孝林,李克永,庞军刚,郭艳琴.2012.鄂尔多斯盆地晚古生代沉积岩源区构造背景及物源分析[J].地质学报,86(7):1150-1162.
CHEN Quanhong, LI Wenhou, HU Xiaolin, LI Keyong, PANG Jungang, GUO Yanqin.2012. Tectonic setting and provenance analysis of Late Palaeozoic sedimentary rocks in Ordos Basin[J]. Acta Geologica Sinica,86(7):1150-1162.

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  • 收稿日期:2011-06-03
  • 最后修改日期:2012-03-02
  • 录用日期:2012-03-05
  • 在线发布日期: 2012-07-10
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