Garnet fractionation,progressive melt loss and bulk composition variations in anatectic metabasites:Complications for interpreting the geodynamic significance of TTGs

作     者：Jillian Kendrick Chris Yakymchuk Jillian Kendrick;Chris Yakymchuk

作者机构：Department of Earth and Environmental SciencesUniversity of WaterlooWaterlooOntarioN2L 3G1Canada 

出 版 物：《Geoscience Frontiers》 (地学前缘（英文版）)

年 卷 期：2020年第11卷第3期

页      面：745-763页

核心收录：

学科分类：070904[理学-构造地质学] 0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 0708[理学-地球物理学] 0704[理学-天文学] 

基　　金：funded by a National Sciences and Engineering Research Council of Canada Discovery grant to CY supported by a Vanier Canada Graduate Scholarship 

主　　题：Archean Anatexis Trace element Phase equilibrium modelling Tectonics 

摘      要：Tonalite-trondhjemite-granodiorite(TTG) suites constitute a large proportion of the Archean geological record;however,the geodynamic processes that generated them,and Archean continental crust in general,remain a subject of *** concentrations and ratios of Sr,Y,La,Yb,Nb,and Ta in TTGs are commonly used to determine the depth of melting of their metabasic *** trace element composition of melt produced by metabasic source rocks during anatexis is strongly affected by the presence and abundance of pressure-sensitive minerals,such as plagioclase(Sr-bearing),garnet(Y-and HREE-bearing),and rutile(Nb-and Ta-bearing).Elevated Sr/Y and La/Yb ratios and low concentrations of Nb and Ta in TTGs are generally considered to indicate melting at high pressures(≥2.0 GPa).The depth of melting is a key factor in determining the origin of TTGs as this provides critical information on the tectonic setting of their *** use phase equilibrium and trace element modelling to explore the effects of three potential influences on TTG trace element compositions:fractionation of trace elements into peritectic garnet cores,progressive melt loss from the source,and source bulk *** model three different compositions of Archean basalts along thermal gradients of 500℃/GPa,750℃/GPa,and 1000℃/*** models produce maj or and trace element melt compositions that are generally consistent with measured compositions of *** Sr/Y,La/Yb,Nb,and Ta exhibit pressure-dependent behaviour,other factors also affect these *** fractionation causes Sr/Y and La/Yb to reach much greater values and in this scenario,the values also increase with increasing *** bulk composition has an effect in all scenarios and most strongly influences La/Yb,Nb,and ***,these results show that Sr/Y,La/Yb,Nb,and Ta can reach values generally considered to be indicative of high pressure melting at a range of P-T conditions including P 2.0 ***,trace ele