地质论评2011，Vol.57Issue(4)：515-531,17.
海南岛中三叠世正长岩—花岗岩套的地质地球化学特征与构造意义
Geological and Geochemical Characteristics of Middle Triassic Syenite-Granite Suite in Hainan Island and Its Geotectonic Implications
摘要
Abstract
In the Hainan Island, the Middle Triassic syenite-granite suite, with outcropped total area of 516km2,was distributed along the Lingshui-Longgnn deep fault and on the southeast side of the Baisha deep fault. It is composed of quartz monzonite, quartz syenite and syenogranite. The suite shows a large variation in their SiO2contents (SiO2 =58.40％ -76.14％ ), and is riched in alkali and K20, with Na2o + K20 =7.10％ - 11.49％and K2O = 3.78％ ～ 7.91％, It belongs to shoshonitic alkaline series. Their A/CNK values range from O. 88 to 1.12, most rocks of the suite belong to sub-aluminous series(A/CNK mostly ＜ 1). Their FeO*/MgO ratios are generally high (3.14 ～ 87. 13 ). Their abundances of rare earth elements change greatly and most of them are relatively high, with REE = 125.5 × 10-6 -980 × 10-6. The REE patterns display right-inclined, with mediumdistinct differentiations between light and heavy rare earth elements. The δEu values are 1.80 ～ O. 06, with positive or insignificant Eu anomaly for the early units, such as the quartz monzonites and quartz syenites, but obvious negative Eu anomaly for the late syenogranites. Rocks of the suite have high Zr, Hf, Zn, F concentrations and (Ga × 104)/Al ,Nb/Ta ratios(20.36 on average). The Ba contents of the early unit rocks are higher but which of the late rocks are lower. Normalized trace element spidergrams demonstrate that negative Sr, P and Ti anomalies are gradually enhanced from early units to late units. Their isotopic compositions of Pb, Sr and Nd are relatively homogenous and are consistent with which of the Middle-Late Triassic mafic intrusions, with n( 206Pb)/n(204Pb) = 18. 487 ～ 18. 586,n(207Pb)/n(204Pb) = 15. 606 - 15. 655, n(208Pb)/n(204Pb) = 38. 503 ～ 38. 635,mean [ n(87Sr)/n(86Sr) ]i, εNd (t) and T2DMis 0.71067, -6.88 and 1575Ma respectively. The suite is classified in A-type granitoids, In which the granites were probably generated from quartz syenitic melt through crystallization differentiations of minerals, such as feldspar, hornblende, apatite, ilmenite, sphene, etc. And the quartz syenitic melt may be derived in the deep crust mainly by differentiation of alkali basaltoid magma which was originated from the EM Ⅱ-type enriched mantle. The suite is considered formed in a post-orogenic extensional tectonic setting.关键词
三叠纪/正长岩-花岗岩套/碱性岩/A型花岗岩/后造山/海南岛Key words
Triassic/ syenite-granite suite/ alkaline/ A-type granite/ post-orogenic/ the Hainan Island引用本文复制引用
周佐民,谢才富,徐倩,高大飞..海南岛中三叠世正长岩—花岗岩套的地质地球化学特征与构造意义[J].地质论评,2011,57(4):515-531,17.基金项目
本文为国家自然科学基金资助项目(编号40572053)和中国地质调查局地质大调查项目(编号200013000127、1212010611803)的成果. （编号40572053）
