华北克拉通北缘中段二叠纪苏吉火山岩及其形成机制  被引量:12

Suzy volcanic rocks in the northern margin of the North China Craton and its formation mechanism

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作  者:董晓杰[1] 王挽琼[2] 沙茜[1] 张金凤[1] 

机构地区:[1]吉林大学地球科学学院,长春130061 [2]西南石油大学地球科学与技术学院,成都610500

出  处:《岩石学报》2016年第9期2765-2779,共15页Acta Petrologica Sinica

基  金:国家自然科学基金项目(41272223;41402169);中国地质调查局项目(1212011220459)联合资助

摘  要:本文报道了集宁北部商都县西井子镇一带苏吉火山岩的岩石学、地球化学、锆石年代学及Hf同位素组成。锆石定年显示,苏吉火山岩形成于早-中二叠世(267±2Ma、272±2Ma和270±3Ma)。研究区内的苏吉火山岩为一套酸性火山岩组合,SiO_2、Al_2O_3含量较高并具有极低的Mg#;其轻稀土元素和大离子亲石元素相对富集,高场强元素Nb、Ta、Ti明显亏损。苏吉火山岩的锆石εHf(t)呈较高的负值(-17.3^-5.9)并具有相当古老的Hf二阶段模式年龄(1667~2386Ma),指示它们的原始岩浆主要源自古老地壳物质的部分熔融。系统的地质填图显示,华北克拉通北缘中段存在一条数百千米的晩古生代火山岩带。苏吉火山岩的形成可能与古亚洲洋向华北克拉通俯冲有关,当时华北克拉通北缘存在一个安第斯型活动大陆边缘。This paper reports the petrology, geochemistry, geochronology and zircon Hf isotope composition of Suzy volcanic rocks, located in Xijingzi, the north of Jining, with the aim of constraining the tectonic nature of the of the northern margin of the North China Plate in Late Paleozoic. Suzy volcanic rocks are composed of rhyolite, rhyolitic pyroclastic rocks and a small amount of andesite. Zircons from the volcanic rocks in Suzy formations are euhedral in shape and display fine-scale oscillatory zoning. Zircon dating show that, Suzy volcanic rocks formed in the Early-Middle Permian (267 ± 2Ma,272 ± 2Ma and 270 ± 3Ma) , which is consistent with the formation age of intrusions distribution in the region. Suzy acidic volcanic rocks characterized with high content of SiO: (71.10% - 76.01% ), Al2O3 ( 12. 60% - 14. 33% ), very low Mg#(8.2 - 17.9) values, and display enrichment in LREE and LILE, depletion in Nb, Ta, Ti, similar chemically to those from an active continental margin setting. Zircons from the Suzy volcanic rocks exhibit negative εHf(t) values from -17.3 to -5.9, old Hf isotopic toM2 from 2386Ma to 1667Ma, indicating that Suzy volcanic rocks were derived from partial melting of ancient crustal material. Its formation may be related to an Andean-type subduction. It' s confirmed there is a hundreds of kilometers long volcanic belt of Late Paleozoic in the central-northern margin of the North China Craton ( NCC ) by geological mapping. Its formation relates to the subduction of the Paleo-Asian Ocean beneath the NCC and there is an Andean-type active continental margin in the northern margin of the NCC.

关 键 词:晚古生代 火山岩 华北克拉通北缘 安第斯型活动大陆边缘 

分 类 号:P588.14[天文地球—岩石学] P597.3[天文地球—地质学]

 

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