Where was the Ailaoshan Ocean and when did it open: A perspective based on detrital zircon U-Pb age and Hf isotope evidence
Where was the Ailaoshan Ocean and when did it open: A perspective based on detrital zircon U-Pb age and Hf isotope evidence
复制标题
DOI：
10.1016/j.gr.2015.08.006
复制
发表时间：
2016-08
影响因子：
6.1
通讯作者：
X. Xia;Xiaosong Nie;Chunkit Lai;Yuejun Wang;X. Long;S. Meffre
中科院分区：
文献类型：
--
作者：
X. Xia;Xiaosong Nie;Chunkit Lai;Yuejun Wang;X. Long;S. Meffre
印度支那-思茅地块和扬子地块被古特提斯洋的一个分支隔开，古生代通常称为哀牢山洋。该哀牢山大洋的残留物被不同程度地提出为沿哀牢山断裂、九家-安定断裂和阿莫江-礼贤江断裂(自东向西)分布。为了验证这些模型，我们对哀牢山带及其邻近的扬子地块西缘寒武纪-泥盆纪沉积单元进行了全面的碎屑锆石U-Pb定年和Hf同位素分析。结果表明，哀牢山-滕条河断裂不同侧碎屑锆石的源区分异明显：断裂以东的碎屑锆石在730~900亿Ma出现一个诊断年龄峰，εHf(T)值具有正负两个特征，Hf模式年龄(Tdmc)峰值在~18.8Ga，而断层以西的碎屑锆石主要以负εHf(T)值为特征，Hf模式年龄(Tdmc)峰值在~21.1Aa。我们的新资料表明，哀牢山-滕条河断裂东西的碎屑可能主要来自扬子地块和印度支那-思茅地块，因此，该断裂可能代表了两个地块之间的实际缝合。我们的研究还表明，哀牢山大洋可能在志留纪早期就开始了早期的大陆裂谷。
The Indochina–Simao and Yangtze blocks were separated by a branch of the Paleo-Tethys Ocean, commonly referred as the Ailaoshan Ocean in the Paleozoic. Remnants of this Ailaoshan Ocean have been variably suggested to locate along (from east to west) the Ailaoshan fault, Jiujia–Anding fault and Amojiang–Lixianjiang fault. In order to test these models, we have carried out comprehensive detrital zircon U–Pb dating and Hf isotope analyses on the Cambrian to Devonian sedimentary units in the Ailaoshan Belt and its adjacent western margin of the Yangtze Block. Our results indicate marked detrital zircon provenance variation on different sides of the Ailaoshan–Tengtiaohe fault: detrital zircons from east of the fault display a diagnostic age peak at 730–900 Ma, which is characterized by both positive and negativeεHf(t) values with a Hf model age (TDMC) peak at ~ 1.8 Ga, whereas detrital zircons from west of the fault display two major age populations of 400–500 and 900–1000 Ma, both characterized by mainly negativeεHf(t) values with a Hf model age (TDMC) peak at ~ 2.1 Ga. Our new data indicate that detritus from east and west of the Ailaoshan–Tengtiaohe fault may have been mainly derived from, respectively, the Yangtze Block and Indochina–Simao blocks, thus suggesting the fault may represent the actual suture between the two blocks. Our study also reveals that the Ailaoshan Ocean may have started its early continental rift in the Early Silurian.