Carboniferous Alaskan-type complex along the Sino–Mongolian boundary,southern margin of the Central Asian Orogenic Belt  

作　　者：Yuruo Shi Linlin Li Alfred Kroner Jing Ding Wei Zhang Zengbao Huang Ping Jian 

机构地区：[1]Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China [2]Institut für Geowissenschaften, Universitat Mainz, 55099 Mainz, Germany [3]Geological Survey of Gansu Province, Lanzhou 735000, China

出　　处：《Acta Geochimica》2017年第2期276-290,共15页地球化学学报（英文）

基　　金：financially supported by the National Natural Science Foundation of China (Grant Nos.40703012,41030314);Geological Survey of China (Grant Nos.1212011120332,DD20160123-05);Chinese Ministry of Science and Technology (Grant 2012FY120100)

摘　　要：We present zircon ages and geochemical data for the Hongshishan Carboniferous Alaskan-type mafic–ultramafic complex exposed in the Beishan area along the Sino–Mongolian boundary, southern margin of the Central Asian Orogenic Belt. This complex mainly consists of dunite,harzburgite, lherzolite, wehrlite, and gabbro, which intrudes Early Carboniferous volcanic rocks and reveals a zoned structure. Zircons of a gabbro sample yielded a 206Pb/238 U age of 357 ± 4 Ma, reflecting the time of Early Carboniferous magmatism. Zircon ages were also obtained for an andesite(322 ± 3 Ma) and a basaltic andesite(304 ± 2 Ma).High initial Nd isotope whole-rock values suggest that the Hongshishan gabbro [e_(Nd(t))= +9.6-+10.2] and basalt[eNd(t)= +10.0-+10.8] were derived from a depleted mantle source. Slightly lower eNd(t)values for the ultramafic rocks [eNd(t)= +8.5-+8.7] suggest some interaction of the parental magma with the continental crust. In contrast, the Late Carboniferous Quershan samples in this area represent subduction-related arc volcanic rocks with Adakite-like compositions. The early Carboniferous Hongshishan Alaskan-type complex was interpreted to represent the remnants of a magma chamber that crystallized at the base of a mature island arc, whereas the Quershan island arc volcanic rockssuggest the resurrection of the subduction process after arccontinent collision and uplift of the roots of the arc.We present zircon ages and geochemical data for the Hongshishan Carboniferous Alaskan-type mafic–ultramafic complex exposed in the Beishan area along the Sino–Mongolian boundary, southern margin of the Central Asian Orogenic Belt. This complex mainly consists of dunite,harzburgite, lherzolite, wehrlite, and gabbro, which intrudes Early Carboniferous volcanic rocks and reveals a zoned structure. Zircons of a gabbro sample yielded a ^206Pb/^238 U age of 357 ± 4 Ma, reflecting the time of Early Carboniferous magmatism. Zircon ages were also obtained for an andesite（322 ± 3 Ma） and a basaltic andesite（304 ± 2 Ma）.High initial Nd isotope whole-rock values suggest that the Hongshishan gabbro [eNd（t）= ＋9.6-＋10.2] and basalt[eNd（t）= ＋10.0-＋10.8] were derived from a depleted mantle source. Slightly lower eNd（t）values for the ultramafic rocks [eNd（t）= ＋8.5-＋8.7] suggest some interaction of the parental magma with the continental crust. In contrast, the Late Carboniferous Quershan samples in this area represent subduction-related arc volcanic rocks with Adakite-like compositions. The early Carboniferous Hongshishan Alaskan-type complex was interpreted to represent the remnants of a magma chamber that crystallized at the base of a mature island arc, whereas the Quershan island arc volcanic rockssuggest the resurrection of the subduction process after arccontinent collision and uplift of the roots of the arc.

关 键 词：Alaskan-type complex CARBONIFEROUS Zircon age Sino-Mongolian boundary CAOB 

分 类 号：P542[天文地球—构造地质学] P588.1[天文地球—地质学]