Ages, Origin and Tectonic Significance of Halaerci Granites from Northeastern Part of Chinese Altay Mountains
Tian Hongbiao
Chen Youxin
Yang Yongqiang
Li Lun
Abstract：In order to study the chronological,geochemical characteristics and tectonic setting of the Halaerci granite from Altay area,the LA-MC-ICPMS zircons U-Pb dating method was employed to assess the ages and Nd isotope composition,preceded by their petrologcial and geochemical studies.In addition,the authors aim to provide more evidences for the structural evolution of Altay tectonic belt by making a comparison with other granites from central Altay orogenic belt.The exposed Halaerci granites of central Altay tectonic belt are dominated by granodiorite,monzonite and syenogranite.LA-ICP-MS zircon U-Pb chronology study suggests that formation age is from 454.8±2.4 Ma (MSWD=0.32),which belongs to the Late Ordovician magma activity.The study of geochemistry indicates that rock is characterized by high silicon,enriched alkali and high potassium (K2 O/Na2 O＞1) and low titanium,low magnesium and low phosphorus.Average (A/CNK) is 1.5 and corundum molecular content of CIPW calculation is greater than 1,which shows a high potassium calc-alkaline peraluminous granite characteristics.The granites are relatively enriched in light rare earth elements,while flat in heavy rare earth elements,with significant Eu negative anomaly,enrichment of Th and Rb,depletion of Sr,Ti and P elements,pronounced Nb,Ta and Ti negative anomalies,which shows the initial arc characteristic of magmatic rocks.Its eNd (t) is close to 0 (-2.0 to 0.5) and old twophase model (TDM2) age (1.15 to 1.35) Ga indicate its source area contains more crust-derived source components with a certain amount mantle source materials.Comprehensive analysis and study suggest that Halaerci granites may be composed of partial melting of argillaceous sandstone enriched with muscovite and biotite under low pressure and high temperature.Its source area has residual plagioclase,ilmenite and apatite and mixed with mantle source materials at the same time.It is concluded that Halaerci granites formed in the active continental margin squeezing environment when the heat by local extentional stress reduction and abnormal uneven mantle materials rise led to partial melting of upper crust to mix with mantle source materials.
Keywords：zircon U-Pb datinggeochemistrytectonic significancegraniteAltay
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：15( 1658-1672 )