Petrologic And Numerical Modeling Study Of Magma Transfer, Storage And Evolution In Emeishan Large Igneous Province

Based on the field work, quantitative textural analysis theory and geochemistry, we studied the magma transfer, storage and evolution by studying basalts, grabbros and granites in Emeishan large igneous province(LIP) in this PhD dissertation. Using these methods, we kwon the five basic variables of time, space, temperature, pressure and composition, and as far as seeks to clarify the magma chemical and physical process. The dissertation made several major achievements and insights as follows:Based on the proposed previously mantle melting column model and its inversion method, we have designed an implication software Calmantle1.0with friend interfaces. Using this software, users can easily obtain the partial melting conditions at the initial and final stages, including temperature, pressure, depth, the degree of partial melting and so on.We report a quantitative textural analysis and bulk-rock geochemical composition of clustered touching crystals (CT-type) and single isolated crystal (SI-type) GPB samples in the Daqiao section. Both types of GPBs are evolved, but have high Ti/Y ratiosand high total FeO content. The two types of GPBs have S-type crystal size distributions but have quite different characteristic lengths. For plagioclase growth rates of10-11to10-10mm/s, The plagioclase megacrysts have the residence time of about500-6,000years, about1,000-10,000years, respectively. We suggest that CT-and SI-type crystals grew and were coarsened in the outer part and inner part of a magma chamber, respectively. Magma evolution during storage is controlled by crystallization, crystal growth, and magma mixing, and pulsating eruptions occur in response to the continuous supply of hot magma and fluid intrusions. The isotopic compositions show they are from EM I.The giant plagioclase gabbros (GPG) dykes mostly intrude into the fine-grained gabbros without significant contact. However, the mineral composition results show that most of the plagioclase megacrysts contain less An than do plagioclase in fine-grained gabbro samples. In situ analyses of Sr isotopes from core-to-rim transects of plagioclase megacrysts are constant, indicating there are no recycling crystals. For a plagioclase growth range of10-11-10-10mm/s, the plagioclase should have a growth time of530-8118years. In a100km3magma chamber releasing thermal energy at a rate of1000MW, Panzhihua intrusion should reach50%crystallization after -2400years. The growth time recorded by the megacrysts in GPG and numerical modelling may constrain the emplacement timescales of Panzhihua intrusion may take place on thousands of years.The Hongge Dalaobao granitic stock in the Emeishan large igneous province, SW China. In situ ziron LA-ICP-MS U-Pb age indicates that the age of monzogranite is257.1±1.7Ma. Based on the deep crustal hot zones, the results of numerical simulation show that the partial melting of deep crust and the Dalaobao granites magmatism are triggered by conductive heating of the mantle-driven magma within3Ma.