辽宁宽甸地区辽河群里尔峪组基性火山岩锆石U-Pb年代学及其地质意义

辽东古元古代构造带内辽河群的形成时代及其演化一直是学者研究的热点.本文对宽甸地区里尔峪组变沉积岩夹层的基性火山岩进行锆石LA-ICP-MS U-Pb年代学研究.7件基性火山岩样品的锆石分为岩浆锆石和变质锆石.测年结果显示代表岩石成岩年龄的岩浆活动有2期:2 150~2 130 Ma、2 050~2 020 Ma，结合本区出露的酸性火山岩，表明宽甸地区辽河群形成时代至少处于2.17~2.03 Ga.获得的5件斜长角闪岩变质年龄显示变质作用发生在1 900 Ma以后，持续时间比较长为1 870~1 780 Ma；进一步可分为3个阶段1 870~1 861 Ma、1 845~1 842 Ma、1 790~1 780 Ma，变质作用峰期为~1 850 Ma，属于本区古元古代第2个强烈的变质峰期，第3阶段与~1 800 Ma左右的变质事件一致.变质闪长岩（D015）脉体形成时代为1 314±24 Ma，斜长角闪岩（D1465-1）变质年龄为1 290±21 Ma，这是首次在辽东地区识别出中元古代岩浆和变质事件，结合辽西和冀北地区1 320~1 380 Ma岩浆活动，认为这些事件是华北板块对Columbia超大陆的裂解过程的响应. 

Zircon U-Pb Geochronology and Its Geological Significance of the Basic Volcanic Rocks from the Li'eryu Formation,Liaohe Group in Kuandian Area,Liaoning Province

The formation age and evolution of the Liaohe Group in the Liao-Ji Paleoproterozoic structural belt have always been a research hotspot. Zircon LA-ICP-MS U-Pb geochronology of basic volcanic rocks intercalated in metamorphic sedimentary rocks of the Li'eryu Formation in Kuandian area is studied. Zircons from seven basic magmatic rocks are divided into magmatic zircons and metamorphic zircons. The dating results show two stages of 2 150－2 130 Ma and 2 050－2 020 Ma, representing the diagenetic age of the rocks. Combined with the acid volcanic rocks exposed in this area, it is considered that the formation age of the Liaohe Group in Kuandian area is at least 2.17－2.03 Ga. The metamorphic ages obtained from five amphibolites show that the metamorphism occurred after 1 900 Ma and lasted from 1 870 to 1 780 Ma, which can be further divided into three phases: 1 870－1 861 Ma, 1 845－1 842 Ma and 1 790－1 780 Ma. The peak period of metamorphism is ~1 850 Ma, which is the second strong metamorphic peak period of Paleoproterozoic in this area. The third stage is consistent with the metamorphic event of ~1 800 Ma. The age of meta diorite (D015) vein is 1 314±24 Ma and metamorphic age of amphibolite (D1465-1) is 1 290±21 Ma. This is the first time that Mesoproterozoic magma and metamorphism events have been identified in eastern Liaoning. Combined with 1 320－1 380 Ma magmatic activity in western Liaoning and northern Hebei, these events are considered as the response of North China Craton to the breakup process of Columbia supercontinent.