Zircon U–Pb geochronological constraints on the Paleoproterozoic crustal evolution of the Eastern block in the North China Craton
Zircon U–Pb geochronological constraints on the Paleoproterozoic crustal evolution of the Eastern block in the North China Craton
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DOI：
10.1016/j.precamres.2006.01.009
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发表时间：
2006-05
影响因子：
3.8
通讯作者：
Xiaoping Lu;Fu-Yuan Wu;Jing-hui Guo;S. Wilde;Jin-Hui Yang;Xiaoming Liu;Xiao Zhang
中科院分区：
文献类型：
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作者：
Xiaoping Lu;Fu-Yuan Wu;Jing-hui Guo;S. Wilde;Jin-Hui Yang;Xiaoming Liu;Xiao Zhang
华北陆块是在1.85Ga左右由东西陆块碰撞形成的。然而，各个区块的详细历史仍然没有解决。东部地块古元古代火山-沉积岩主要出露于沿着东缘，在辽东半岛称辽河群，在吉林南部通化地区称光华群、集安群和老岭群。广化群、吉安群以火山岩产出为特征，老岭群以碎屑岩和碳酸盐岩产出为特征。LA-ICP-MS和SHRIMP锆石U-Pb同位素年龄测定结果表明，光华群和吉安群形成于2.1 ~ 2.0Ga之间，而老岭群可能形成于2.5- 2.2Ga和2.0-1.9Ga两个时期。现有资料表明，集安群、老岭群和辽河群地层混乱，没有共同的地层，变形强烈，难以确定原始分层和接触关系。结合侵入岩的年龄资料，辽吉地区古元古代的构造演化可能与南起辽南地块、北起龙岗地块的碰撞拉张作用有关。龙岗地块的伸展作用发生在2.12-1.98Ga，以光华基性火山岩的喷发为代表。辽南地块的伸展作用则表现为2.16-2.09Ga的A型花岗岩和2.12-1.98Ga的吉安群火山-沉积岩。这两个块体在1.93-1.90Ga发生碰撞，导致北半球记录到顺时针变质P-T轨迹。辽河-老岭群的碰撞后演化为约1.85Ga的逆冲变质P-T轨迹和南秦岭的巨型花岗质侵入体。辽河-集安群。因此，认为龙岗-辽南碰撞的时间略早于1.85Ga，即华北克拉通由东西两块体的碰撞拼合而成。
The North China Craton (NCC) is proposed to have formed by collision between the Western and Eastern blocks at ∼1.85Ga. However, the detailed history of the individual blocks remains unsolved. In the Eastern block, the Paleoproterozoic volcano-sedimentary rocks are mainly exposed along its eastern margin, and are referred to as the Liaohe Group in the Liaodong Peninsula of Liaoning Province and as the Guanghua, Ji’an and Laoling Groups in the Tonghua area of southern Jilin Province. The Guanghua and Ji’an Groups are characterized by the occurrence of volcanic rocks, whereas the Laoling Group is composed of clastic sediments and carbonates. Zircon U–Pb isotopic dating by LA-ICP-MS and SHRIMP methods indicates that the Guanghua and Ji’an Groups were formed between 2.1 and 2.0Ga, but that the rocks of the Laoling Group may have formed in two episodes at 2.5–2.2 and 2.0–1.9Ga, respectively. The present data indicate that the Ji’an, Laoling and Liaohe Groups are chaotic, without a common stratigraphy, with intense deformation making it difficult to identify original layering and contact relationships. Combined with age data from rocks intrusive into the sequence, the Paleoproterozoic tectonic evolution of the Liaoning–Jilin area can be related to collision and extension between the Liaonan block to the south and the Longgang block to the north. Extension in the Longgang block occurred at 2.12–1.98Ga and was represented by eruption of the Guanghua mafic volcanic rocks. However, extension in the Liaonan block is expressed by 2.16–2.09Ga A-type granites and ∼2.12–1.98Ga volcano-sedimentary rocks of the Ji’an Group. These two blocks collided at ∼1.93–1.90Ga, resulting in a clockwise metamorphic P–T path recorded in the N. Liaohe–Laoling Groups, followed by ∼1.85Ga post-collisional evolution expressed by anticlockwise metamorphic P–T paths and immense granitic intrusions in the S. Liaohe–Ji’an Groups. Therefore, it is suggested that the collision between the Longgang and Liaonan in the Eastern block of the NCC occurred a little earlier than ∼1.85Ga, when the NCC amalgamated by collision of the Western and Eastern blocks.