Petrogenesis and geological significance of Late Jurassic Shaxin granite in northern Hainan:Constraints from chronology,geochemistry and Sr-Nd-Hf isotopes
Jurassic igneous rocks in Hainan Island are located in the southwest end of the Jurassic magmatic belt of South China,which are the key probes to constrain the Late Mesozoic magmatic dynamic settings in South China and the subduction dynamic processes of the Paleo-Pacific oceanic slab.This study presents systematic petrological,chronological,geochemical,whole rock Sr-Nd isotopic and zircon Lu-Hf isotopic studies on the Jurassic Shaxin granite pluton in northern Hainan Island,aiming to reasonably explore its petrogenesis and geological significance.The Shaxin pluton mainly comprises by medium to fine-grained biotite monzogranite.LA-ICP-MS zircon U-Pb dating reveals that the Shaxin pluton was formed at 161±1 Ma,belonging to the Late Jurassic magmatism.The Shaxin pluton has SiO2 contents of 70.73％～75.15％and total alkali contents of 7.64％～8.31％(K2O+Na2O).The studied rocks have low contents of Ca,Mg,and Fe with an average A/CNK value of 1.06,belonging to the high potassium,calc-alkaline,and weakly peraluminous rocks.They are enriched in light rare earth elements(75.35×10-6～112.71×10-6)but are depleted in heavy rare earth elements(6.40×10-6～8.6310-6)with insignificant europium anomaly(δEu=0.87～1.10).The Shaxin pluton has high εNd(t)values(-2.7～-1.9)and low two-stage Nd model ages(1.17～1.10 Ga).The studied rocks show high zircon εHf(t)ratios(-1.71～+1.84)and low two-stage Hf model ages(1.32～1.09 Ga).The rocks have low high-field-strength elements(Zr+Nb+Ce+Y)contents(123×10-6～217×10-6),TFeO/MgO values(3.39～5.08)and zircon saturation temperatures(724 ℃～772 ℃),and lack the typical peraluminous minerals.Comprehensive study indicate that the Shaxin granites belong to the Ⅰ-type granite,and are derived by from the partial melting of late Mesoproterozoic metamorphic sandstone with the input of minor mantle-derived materials in a continental arc environment related to the rollback of the Paleo-Pacific Plate.
ChronologyGeochemistryLate JurassicⅠ-type granitesHainan Island
万方数据
维普
