Zircon U-Pb and Hf isotopic constraints on the Early Archean crustal evolution in Anshan of the North China Craton
Zircon U-Pb and Hf isotopic constraints on the Early Archean crustal evolution in Anshan of the North China Craton
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锆石U-Pb和Hf同位素对华北克拉通鞍山早太古代地壳演化的约束
DOI：
10.1016/j.precamres.2008.10.002
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发表时间：
2008-12
影响因子：
3.8
通讯作者：
中科院分区：
文献类型：
--
作者：
华北陆壳是世界上少数几个存在大于3.8Ga地壳物质的地区之一，在鞍山白家坟和东山片麻岩中发现了该年龄的锆石。然而，该地区是否存在3.8Ga的岩石一直受到质疑，因为单个岩石样品中存在各种较年轻的锆石，而年龄为3.8Ga的锆石很少，可以解释为继承性的。利用阴极发光成像和SHRIMP U-Pb定年相结合的方法研究了白家坟和东山片麻岩中的锆石，结果表明白家坟和东山片麻岩记录了多期花岗质岩浆活动。最古老的岩浆事件是由一个年龄为3887± 5 Ma的锆石记录的，随后的岩浆事件发生在3.8Ga（3808±24，3798±30，3802±11和3799± 6 Ma），证实了该地区存在3.8Ga物质。下一次岩浆事件发生在1.36 -3.7Ga。然而，所有样品都含有年龄为3.1-3.3Ga的年轻锆石，尽管它们含有少量年龄为3.6-3.8Ga的锆石颗粒。3.1-3.3Ga锆石显示出典型的岩浆振荡环带，没有显示出任何变质作用的证据，表明这些样品分别在3.3和3.1Ga侵位，年龄较老的锆石解释为继承性成因。因此，3.8Ga岩石的暴露量比以前认为的要小得多。原位锆石Hf同位素分析表明，这些花岗质岩石起源于幼年地壳，地壳生长的年龄峰值分别为3.4，3.6和3.9Ga，没有证据表明存在4.0Ga以上的地壳物质。
The North China Craton is one of the few places in the world where >3.8Ga crustal material exists, since zircons of this age have been found in the Baijiafen and Dongshan gneisses from Anshan in northeastern China. However, it has been questioned whether any 3.8Ga rock exists in the area, since various younger zircons exist within single rock samples, and zircons with age of ∼3.8Ga are few and can be interpreted as inherited in origin. A study of zircons using combined cathodoluminescence imaging and SHRIMP U–Pb dating indicates that the Baijiafen and Dongshan gneisses record several stages of granitic magmatism. The oldest magmatic event is recorded by a zircon with an age of 3887±5Ma, with a subsequent magmatic event at 3.8Ga (3808±24, 3798±30, 3802±11 and 3799±6Ma), confirming the existence of 3.8Ga materials in the area. The next magmatic event took place at ∼3.6–3.7Ga. However, all samples contain younger zircons with ages of 3.1–3.3Ga, although they contain a few zircon grains with ages of ∼3.6–3.8Ga. The 3.1–3.3Ga zircons show typical igneous oscillatory zoning and do not show any evidence that were produced by metamorphism, indicating that these samples were emplaced at 3.3 and 3.1Ga, respectively and the zircons with older ages are interpreted as inherited in origin. The exposure of 3.8Ga rock is therefore much smaller than previously thought. In situ zircon Hf isotopic analyses indicate that these granitic rocks were derived from juvenile crust with age peaks of crustal growth at ∼3.4, 3.6 and 3.9Ga, there is no evidence for existence of crustal material older than 4.0Ga.
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影响因子：
3.1
作者：
A. Nutman;C. Friend;V. Bennett
通讯作者：
A. Nutman;C. Friend;V. Bennett
影响因子：
3.9
作者：
Cherniak, DJ;Hanchar, JM;Watson, EB
通讯作者：
Watson, EB
影响因子：
5
作者：
W. Peck;J. Valley;S. Wilde;C. Graham
通讯作者：
W. Peck;J. Valley;S. Wilde;C. Graham
影响因子：
1.4
作者：
L. Schiøtte;W. Compston;D. Bridgwater
通讯作者：
L. Schiøtte;W. Compston;D. Bridgwater
影响因子：
3.8
作者：
Xiaoping Lu;Fu-Yuan Wu;Jing-hui Guo;S. Wilde;Jin-Hui Yang;Xiaoming Liu;Xiao Zhang
通讯作者：
Xiaoping Lu;Fu-Yuan Wu;Jing-hui Guo;S. Wilde;Jin-Hui Yang;Xiaoming Liu;Xiao Zhang