Volcanic rocks in the Bangxi-Chenxing tectonic zone provide important carries for better understanding the Late Paleozoic tectonic evolution in Hainan and its temporal-spatial pattern of the eastern Paleotethyan evolu...Volcanic rocks in the Bangxi-Chenxing tectonic zone provide important carries for better understanding the Late Paleozoic tectonic evolution in Hainan and its temporal-spatial pattern of the eastern Paleotethyan evolution. This paper presents a set of new geochronological and geochemical data on the andesitic and dacitic rocks along the Bangxi-Chenxing tectonic zone in central Hainan. The rep- resentative andesitic and dacitic samples yield similar zircon U-Pb ages of 353^-3 and 351^-7 Ma, respec- tively, being of Early Carboniferous origin. These volcanic rocks are characterized by low TiO2 and high A1203 contents and are enriched in LILEs and LREEs but depletion in HFSEs, along with negative fNd（t） Values of =1.4-- -4.7 and high STSr/S6Sr（i） ratios of 0.707 2-0.710 1. Geochemical signatures suggest that the andesitic and dacitic samples might originate from a metasomatized wedge modified by the slab-derived component in a continental arc setting. In combination with the available data, it is pro- posed for the development of a Carboniferous continental arc in response to the eastern Paleotethyan evolution. The Bangxi-Chenxing tectonic zone might westerly link with the Jinshajiang-Ailaoshan-Song Ma suture zone, constituting an assemblage boundary between the South China and Indochina blocks.展开更多
基金jointly supported by the Projects from China (Nos. U1701641, 41506050, 2016ZT06N331 and 2017M612794)
文摘Volcanic rocks in the Bangxi-Chenxing tectonic zone provide important carries for better understanding the Late Paleozoic tectonic evolution in Hainan and its temporal-spatial pattern of the eastern Paleotethyan evolution. This paper presents a set of new geochronological and geochemical data on the andesitic and dacitic rocks along the Bangxi-Chenxing tectonic zone in central Hainan. The rep- resentative andesitic and dacitic samples yield similar zircon U-Pb ages of 353^-3 and 351^-7 Ma, respec- tively, being of Early Carboniferous origin. These volcanic rocks are characterized by low TiO2 and high A1203 contents and are enriched in LILEs and LREEs but depletion in HFSEs, along with negative fNd（t） Values of =1.4-- -4.7 and high STSr/S6Sr（i） ratios of 0.707 2-0.710 1. Geochemical signatures suggest that the andesitic and dacitic samples might originate from a metasomatized wedge modified by the slab-derived component in a continental arc setting. In combination with the available data, it is pro- posed for the development of a Carboniferous continental arc in response to the eastern Paleotethyan evolution. The Bangxi-Chenxing tectonic zone might westerly link with the Jinshajiang-Ailaoshan-Song Ma suture zone, constituting an assemblage boundary between the South China and Indochina blocks.
文摘泰国北部清孔地区存在着大量的火山岩,前人将其划归二叠纪-三叠纪.运用LA-ICP-MS的方法,对清孔地区代表性的火山岩进行了锆石U-Pb年代学研究.其中Doi Yao带玄武质安山岩TL-1-B和TL-31-B锆石年龄分别为241.1±6.9Ma和241.1±3.9Ma,Doi Khun Ta Khuan带流纹岩TL-32-B1锆石年龄为238.0±8.9Ma,三者均为中三叠世早期.这组U-Pb同位素年龄与云南景洪地区和泰国南邦地区的弧火山形成年龄相近,指示泰国北部清莱弧火山岩带从南邦地区,经清孔地区,向北延伸到了景洪地区的澜沧江弧火山岩带.另外,研究区还发现(1885±16～1323±13)Ma的U-Pb同位素年龄,表明该区存在古元古代-中元古代的基底.
