K-Ar Dating of Fault Gouges from the Red River Fault Zone of Vietnam  

作　　者：BUI Hoang Bac NGO Xuan Thanh Yungoo SONG Tetsumaru ITAYA Koshi YAGI KHUONG The Hung NGUYEN Tien Dung 

机构地区：[1]Faculty of Geosciences and Geoengineering, Hanoi University of Mining and Geology, Duc Thang, Bac Tu Liem, Hanoi, Vietnam [2]Department of Earth System Sciences, Yonsei University, 50 Yonsei-ro, Seoul 120-749, Republic of Korea [3]Japan Geochronology Network (NPO), 2-5 Nakashima, Naka-ku, Okayama 703-8252, Japan [4]Hiruzen Institute for Geology and Chronology, Co., Ltd., 2-5 Nakashima, Nakaku, Okayama 703-8252, Japan

出　　处：《Acta Geologica Sinica(English Edition)》2016年第5期1653-1663,共11页地质学报（英文版）

基　　金：financially supported by the Vietnam National Foundation for Science and Technology Development(NAFOSTED) under grant number 105.032011.11 to Bui Hoang Bac

摘　　要：Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.

关 键 词：ILLITE K-Ar dating Red River Fault Zone POLYTYPE GOUGE authigenitic 

分 类 号：P542[天文地球—构造地质学]