Palaeozoic pre- and post-collision calc-alkaline magmatism in the Qinling orogenic belt, central China, as documented by zircon ages on granitoid rocks
Palaeozoic pre- and post-collision calc-alkaline magmatism in the Qinling orogenic belt, central China, as documented by zircon ages on granitoid rocks
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DOI：
10.1144/gsjgs.153.3.0409
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发表时间：
1996-05
影响因子：
2.7
通讯作者：
F. Xue;A. Kröner;T. Reischmann;F. Lerch
中科院分区：
文献类型：
--
作者：
F. Xue;A. Kröner;T. Reischmann;F. Lerch
在大比例尺普查填图的基础上，我们在北方秦岭造山带中识别出两个钙碱性深成岩组合。中国中部。更古老的侵入体组合。与寄主火山弧序列密切共生、变形一致，似为玄武质弧岩浆分异作用的产物。因此，它早于华北地块与中秦岭岛弧系统的碰撞，该岛弧系统发育在华北地块以南的西南太平洋型洋域中。单颗粒锆石207 Pb/206 Pb蒸发测年结果表明该组合的年龄为早中奥陶世。相对较小的变化范围为487.2 ± 1.1 ~ 470.2 ± 1.3Ma。较年轻的组合的侵入体基本上是未变形的，在较老的组合的岩石中显示出截形结构。它们被解释为后碰撞钙碱性花岗岩类。单颗粒锆石定年结果为401.8 ± 0.8Ma。与早期的工作一致，该工作定义了从C. 420 ~ 395 Ma。我们的数据有利于一个构造模型，涉及形成和合并的岛弧和微大陆之间的约。490和470 Ma前形成中秦岭带，随后在c.四百年前。扬子陆块北方边缘的花岗质片麻岩的晚前寒武纪年龄为762.0 ± 0.7 Ma，支持冈瓦纳大陆与该大型陆块的亲缘关系。
Based on large-scale reconnaissance mapping, we identified two calc-alkaline plutonic assemblages from the northern Qinling orogenic belt. central China. The older assemblage of intrusions. closely associated and deformed coevally with their host volcanic arc sequences, seems to represent the fractionation product of basaltic arc magma. It therefore predates the collision of the North China Block with the Central Qinling island-arc system that developed in a SW Pacific-type oceanic domain south of the North China Block. Single-zircon 207Pb/206Pb evaporation dating yielded early to middle Ordovician ages for this assemblage. with a relatively small range from 487.2 ± 1.1 to 470.2 ± 1.3 Ma. Intrusions of the younger assemblage are largely undeformed and truncate structures shown in rocks of the older assemblage. They are interpreted as post-collisional calc-alkaline granitoids. Single zircon dating provided an age of 401.8 ± 0.8 Ma for the younger assemblage. consistent with earlier work that defines an age range from c. 420 to 395 Ma. Our data favour a tectonic model involving formation and amalgamation of island arc and microcontinent terranes between ca. 490 and 470 Ma ago to create the Central Qinling Zone which subsequently collided with the North China Block prior to c. 400 Ma ago. A late Precambrian age of 762.0 ± 0.7 Ma for a granitoid gneiss at the northern margin of the Yangtze Block supports a Gondwana affinity for this large continental block.