内蒙古乌拉特中旗哈达呼舒基性岩体形成的构造背景与古亚洲洋的早期俯冲历史
Tectonic Setting of Hadahushu Mafic Intrusion in Urad Zhongqi Area, Inner Mongolia: Implications for Early Subduction History of Paleo-Asian Ocean Plate

内蒙古乌拉特中旗地区在大地构造上横跨华北板块边缘和兴蒙造山带，区域基性岩体多以小岩株形式产出，侵入时代缺少可靠的资料.对乌拉特中旗哈达呼舒基性岩进行锆石U-Pb年代学、岩石地球化学以及Hf同位素研究，对其岩石成因和古亚洲洋板块俯冲作用的开始时间给予制约.哈达呼舒基性岩锆石LA-ICP-MS U-Pb定年结果表明，该岩体形成于晚寒武世(513±2Ma).在地球化学上，它们属于钙碱性系列，富集大离子亲石元素(如K、Rb、Ba)，〖JP2〗亏损高场强元素(如Nb、Ta、Zr、Ti)和LREE.岩石的εHf(t)值为14.15～15.03，单阶段模式年龄(TDM1)为518～556Ma，与岩石原岩形成时代513Ma相近，认为其原始岩浆起源于亏损岩石圈地幔.综合区域同时代火成岩的研究成果，认为哈达呼舒基性岩体形成于古亚洲洋俯冲消减环境.
The Urad Zhongqi area of western Inner Mongolia crosses the North China Plate margin and Xing'an-Mongolia Orogenic Belt, which distributed regional basic rock massif occurred as small stocks, and a lack of reliable data of intrusion age. This paper reports LA-ICP-MS zircon U-Pb dating, geochemical and Hf isotopic data of Hadahushu mafic intrusion in Urad Zhongqi area, with the aim of constraining its petrogenesis and the beginning time of subduction of the Paleo-Asian oceanic plate. LA-ICP-MS U-Pb dating results of zircons from the mafic intrusion indicate that the intrusion formed at the Late Cambrian (513±2Ma). The geochemical characteristics of these rocks indicate that they are the calc-alkaline series, and are characterized by enrichment in LILE (such as K, Ba, Rb), 〖JP2〗relatively depleted in HFSE (such as Nb, Ta, Zr, Ti) and LREE. The εHf(t) values and one-stage model ages (TDM1) of zircons from the rock vary from 14.15 to 15.03 and from 518 to 556 Ma, respectively. These characteristics suggest that the primary magma was derived from the depleted lithospheric mantle source. Based on the previous study, we conclude that the formation of mafic intrusion was related to the subduction of the Paleo-Asian oceanic plate