Genesis of Highly Fractionated Ma’anshan Rock in Zhejiang and Anhui Provinces Constrained by U-Pb Zircon Geochronology and Geochemistry
Zhang Jianfang
Wang Longwu
Chen Jinhua
Zhu Chaohui
Liu Jian
Zhang Mingyuan
Abstract：To understand the genesis of Ma'anshan rock composed of early period pegmatite and megacryst porphyritic adamel-lite,medium period fine granite and late period granite porphyry dykes,intrusion epochs are confirmed using SHRIMP and LA-ICP-MS zircon U-Pb methods.The dating shows that the pegmatite porphyritic adamellite is 132.2±1.6 Ma (MSWD=1.9, n =1 1),the megacrysts porphyritic adamellite 127.7 ±1.2 Ma (MSWD=1.1,n =10),the fine-grained granite 128.3±1.1 Ma (MSWD=1.7,n =10)and the granite porphyry dykes 127.4±1.8 Ma (MSWD=0.77,n =1 1).Rock geochemistry shows that the rock from early to late has the characteristic of alkali series shoshonite series evolving to high potassium calc (during evolu-tion ),whereas the differentiation degree gradually increases.The porphyritic adamellites have the characteristics of high ΣREE content,obvious differentiation between light rare earth and heavy rare earth elements ,with a strong negative Eu anomaly and weak rightward REE distribution patterns.It is enriched in elements of K,Th,U,Rb and weakly depleted in Ba,Sr,P,Nb, Ta,Ti.The fine-grained granite and granite porphyry dyke have the characteristics of lower ΣREE content,not obvious differ-entiation between light and heavy rare earth elements,with a strong negative Eu anomaly,and “V”-type REE distribution pat-terns.It is enriched in elements of K,Th,U,Rb,strongly depleted in Ba,Sr,P,Nb,Ti.Ma'anshan rock was formed by the function of partially molten magma emplacement successively crystallization differentiation and it is the product of intraconti-nental extension after the Early Cretaceous subduction orogeny in Northwest Zhejiang-South Anhui,with the characteristic of highly fractionated I-type granites.
Keywords：zircon U-PbgeochemistrypetrogenesisMa'anshan rockZhejiang and Anhui border area
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：17( 98-114 )