Petrogenesis of volcanic rocks from Eastern Manus Basin: indications in mineralogy and geochemistry

作者：Xia ZHAO,Liyan TIAN,Jianhui SUN,Peng HUANG,Yan LI,Yue GAO

摘要：To understand the petrogenesis and magma evolution history in the Eastern Manus Basin(EMB),geochemistry of pyroxene and plagioclase mineral phenocrysts in basaltic andesites and dacites were reported.The plagioclase-melt thermometry showed that,plagioclase in dacites crystalized in 1027.2–1028.5°C under 3.37–5.08 kbar,whereas in basaltic andesite was 1181.4–1187.0°C under 1.79–4.46 kbar.Pyroxene compositions and invariable La/Sm vs La values of whole rock powders indicate that lavas were erupted in rapid cooling rate and mainly controlled by fractional crystallization(FC).In addition,oscillatory zonings in plagioclase and pyroxene phenocrysts indicated small local perturbations and degassing episodes in the magma chamber.Some high Mg#clinopyroxene antecrysts were found in EMB lavas.The highest Mg#of parental EMB melts is 69,which falls into the range of initial partial melts from upper mantle peridotite source(68–75).In terms of isotopic compositions,the EMB lavas most likely originated from Indian-type MORB mantle which was infl uenced by subduction components.In details,the subduction components are mainly derived from the dehydration of a subducted altered oceanic crust,and the contribution of sediment infl uence is minor.The Pb isotopic compositions and end member modeling further suggest that the source of subduction components is more likely from the Pacifi c Plate instead of the Solomon Plate.

发文机构：CAS Key Laboratory for Experimental Study under Deep-sea Extreme Conditions Key Laboratory of Marine Geology and Environment University of Chinese Academy of Sciences Center for Ocean Mega-Science Laboratory for Marine Geology

关键词：EasternManusBasinPLAGIOCLASEPYROXENEwholerockSr-Nd-Pbisotopemagma

分类号： P58[天文地球—岩石学]