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

论文摘要

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 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.

论文目录

• 0 INTRODUCTION
• 1 GEOLOGICAL BACKGROUND
• 2 ANALYTICAL METHODS
•   2.1 LA-ICP-MS Zircon U-Pb Dating
•   2.2 In situ Zircon Hf Isotope Analyses
•   2.3 Whole-Rock Elemental and Nd Isotope Analyses
• 3 ANALYTICAL RESULTS
•   3.1 Zircon Morphology, U-Pb Ages and Hf Isotopes
•   3.2 Major and Trace Elements
•   3.3 Nd Isotope Compositions
• 4 DISCUSSION
•   4.1 Petrogenesis of the High-K Granitoids
•   4.2 Neoarchean Tectonic Implications for the NCC
•   4.3 Reworking of the Continental Crust
• 5 CONCLUSION

文章来源

类型: 期刊论文

作者: Lei Li,Wenjian Zhai

来源: Journal of Earth Science 2019年03期

年度: 2019

分类: 基础科学

专业: 地质学

单位: State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,No.1 Geology and Mineral Resources Survey Institute of Henan Geology and Mineral Exploration and Development Bureau,Henan Institute of Geological Survey

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)

分类号: P588.1;P597.3

页码: 647-665

总页数: 19

文件大小: 1028K

下载量: 25