Geochronology and Geochemistry Characteristics of Jiuhuashan Intrusion Rocks in Quzhou,Zhejiang Province
The Jiangshan-Shaoxing tectonic belt is characterized by the development of numerous Late Cretaceous acidic volcanic-intrusive rock masses,such as Baijuhua granite,Cuishan granite,and Dazhou rhyolite.Previous studies on the chronology of these rocks indicate that they were formed between 137～126 Ma,and the geochemical studies show that these rock masses have geochemical characteristics of A-type granites.These studies are of significant geological importance for understanding the genesis and tectonic background of the rock bodies in the Jiangshan-Shaoxing tectonic belt.Based on the regional geological survey in the Jiuhuashan area of western Zhejiang Province,LA-ICP-MS zircon U-Pb dating of Jiuhuashan granite rock mass was carried out,the results indicate that the Jiuhuashan rock mass was formed in(132.7±4.3)Ma,which is the product of early Cretaceous volcanic activity.By means of isotope chronology and rock geochemistry,the diagenetic age of Jiuhuashan rock mass was re-dissected,its geochemical charateristics and Sr-Nd isotope charateristics were analyzed,and the magma source area was discussed.The results show that the Jiuhuashan rock mass has the characteristics of high silicon,rich aluminum alkali,relatively high potassium and low sodium,and low calcium and magnesium.The content of SiO2 is 68.58%～72.21%,which has the characteristics of quasi-aluminous-peraluminous and high-potassium calc-alkaline-basalt series.The distribution of trace elements shows significant negative anomalies in Sr,Ba,Ti,and P,and the distribution of rare earth elements shows obvious negative Eu anomalies,which has the typical features of A-type granites.The εNd(t)values of the rock samples range from-6.3 to-5.8,with an average value of-6.0 and the two-stage model age TDM2(Nd)ranges from 1.34 Ga to 1.43 Ga,with an average of 1.40 Ga.The results show that the magma source of the rock mass is mainly the Mesoproterozoic basement,but some mantle-derived material is added,which has the characteristics of crust-mantle mixing.
Jiuhuashan granite rock masszircon U-Pb datingrock geochemistryA-type graniteZhejiang Province
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