Geochemistry and Petrogenesis of the ca. 2.5Ga High-K Granitoids in the Southern North China Craton  

作　　者：Lei Li Wenjian Zhai 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China [2]No.1 Geology and Mineral Resources Survey Institute of Henan Geology and Mineral Exploration and Development Bureau, Luoyang 471023, China [3]Henan Institute of Geological Survey,Zhengzhou 450001, China

出　　处：《Journal of Earth Science》2019年第3期647-665,共19页地球科学学刊（英文版）

基　　金：supported by the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (No. MSFGPMR16);the Key Program of the Ministry of Land and Resources of China (No. 1212011220497)

摘　　要：Archean high-K granitoids, generally formed after tonalite-trondhjemite-granodiorite (TTGs), are important for understanding crustal reworking of ancient cratons. The Linshan Archean high-K granitoids from the southern Trans-North China Orogen (TNCO) provide a window into the conti-nental crustal evolution of the North China Craton (NCC). They mainly consist of monzogranite and granodiorite which were formed during 2 542-2 503 Ma. The high-K granitoids have high SiO2 (65.86wt.%-78.08wt.%), K2O (3.29 wt.%-7.62wt.%) and low P2O5 (0.01 wt.%-0.27wt.%). They display right inclined REE patterns with negative Eu anomalies (Eu/Eu*=0.20-0.81).Their spider diagram is characterized by enrichment of Rb, K, Th, U and depletion of Nb, Ta, Zr, Ti. The rocks have positive and variable zircon εHf(t)(+2.5 to +6.6) and whole-rock εHf(t)(+0.7 to +4.5) with two-stage model ages (TDM2^Hf=2.87-2.64 Ga;TDM2^Nd=2.77-2.50 Ga) similar to those of the Archean TTG-ty pe rocks, amphibolites and diorites in the area. These evidences suggest that the high-K granitoids were produced by partial melting of juvenile crustal rocks. The Linshan high-K granitoids show relatively high whole-rock zircon saturation tempera-tures (694-889℃) and low Sr/Y ratios (0.27-21.1), indicating low pressure partial melting. Combined with other geological evidences, the Linshan high-K granitoids are suggested to have been produced by partial melting of the continental crust in a post-collision extensional environment after an arc-continent collision. Thus, the NCC did not amalgamate together until ca. 2.5 Ga. Compiled zircon U-Pb ages and Hf isotopes reveal that the ca. 2.5 Ga magmatism represents reworking of the continental crust.Archean high-K granitoids,generally formed after tonalite-trondhjemite-granodiorite（TTGs）,are important for understanding crustal reworking of ancient cratons.The Linshan Archean high-K granitoids from the southern Trans-North China Orogen（TNCO）provide a window into the continental crustal evolution of the North China Craton（NCC）.They mainly consist of monzogranite and granodiorite which were formed during 2 542–2 503 Ma.The high-K granitoids have high Si O2（65.86wt.%–78.08 wt.%）,K2O（3.29 wt.%–7.62 wt.%）and low P2O5（0.01 wt.%–0.27 wt.%）.They display right inclined REE patterns with negative Eu anomalies（Eu/Eu*=0.20–0.81）.Their spider diagram is characterized by enrichment of Rb,K,Th,U and depletion of Nb,Ta,Zr,Ti.The rocks have positive and variable zirconεHf（t）（+2.5 to+6.6）and whole-rockεNd（t）（+0.7 to+4.5）with two-stage model ages(THfDM2=2.87–2.64Ga;TNdDM2=2.77–2.50 Ga)similar to those of the Archean TTG-type rocks,amphibolites and diorites in the area.These evidences suggest that the high-K granitoids were produced by partial melting of juvenile crustal rocks.The Linshan high-K granitoids show relatively high whole-rock zircon saturation temperatures（694–889oC）and low Sr/Y ratios（0.27–21.1）,indicating low pressure partial melting.Combined with other geological evidences,the Linshan high-K granitoids are suggested to have been produced by partial melting of the continental crust in a post-collision extensional environment after an arc-continent collision.Thus,the NCC did not amalgamate together until ca.2.5 Ga.Compiled zircon U-Pb ages and Hf isotopes reveal that the ca.2.5 Ga magmatism represents reworking of the continental crust.

关 键 词：GRANITOIDS PETROGENESIS NEOARCHEAN North China CRATON 

分 类 号：P[天文地球]