Unlike the typical large igneous provinces(LIPs) that are dominated by mafic-ultramafic rocks, the Tarim large igneous province(TLIP) is characterized by a high proportion of felsic rocks, based on which the TLIP is c...Unlike the typical large igneous provinces(LIPs) that are dominated by mafic-ultramafic rocks, the Tarim large igneous province(TLIP) is characterized by a high proportion of felsic rocks, based on which the TLIP is classified as a transitional LIP. In this study, we focus on the trachydacite from the TLIP in which we report the characteristics of hisingerite employing a variety of techniques such as EMPA, LA-ICPMS, CCD single crystal diffraction, and bulk-rock oxygen isotopes. The hisingerite in this rock is associated with plagioclase, amphibole, apatite and ilmenite. These minerals occur as aggregates of fine curled fibers in micron-scale and display heavy rare earth elements(HREE) enriched signature with significant negative Eu anomalies. In the primitive mantle-normalized trace element spider diagrams, they show pronounced Th and U spikes and Nb, Zr, Hf troughs. Petrological observation and mineralogical study reveal a closely genetic relationship between hisingerite and amphibole, indicating that the hisingerite might have been derived from the breakdown of amphibole during the magma ascent. The formation of hisingerite requires excess water from the surrounding melts, suggesting a hydrous parental magma. The hisingerite and amphibole assign a hydrous crustal source for the rock, and extensive crustal melting accounts for the voluminous felsic rocks in the TLIP.展开更多
基金the National Natural Science Foundation of China (Nos. 41772057, 41702064)the Fundamental Research Funds for the Central Universities (Nos. 2652018118, PA2018GDQT0020)。
文摘Unlike the typical large igneous provinces(LIPs) that are dominated by mafic-ultramafic rocks, the Tarim large igneous province(TLIP) is characterized by a high proportion of felsic rocks, based on which the TLIP is classified as a transitional LIP. In this study, we focus on the trachydacite from the TLIP in which we report the characteristics of hisingerite employing a variety of techniques such as EMPA, LA-ICPMS, CCD single crystal diffraction, and bulk-rock oxygen isotopes. The hisingerite in this rock is associated with plagioclase, amphibole, apatite and ilmenite. These minerals occur as aggregates of fine curled fibers in micron-scale and display heavy rare earth elements(HREE) enriched signature with significant negative Eu anomalies. In the primitive mantle-normalized trace element spider diagrams, they show pronounced Th and U spikes and Nb, Zr, Hf troughs. Petrological observation and mineralogical study reveal a closely genetic relationship between hisingerite and amphibole, indicating that the hisingerite might have been derived from the breakdown of amphibole during the magma ascent. The formation of hisingerite requires excess water from the surrounding melts, suggesting a hydrous parental magma. The hisingerite and amphibole assign a hydrous crustal source for the rock, and extensive crustal melting accounts for the voluminous felsic rocks in the TLIP.
