红石泉白岗岩地球化学特征及其构造意义

红石泉地区位于龙首山西部,对研究区内白岗岩进行了详细的岩相学和地球化学分析,以探讨其岩石成因、岩浆源区特征和大地构造背景.结果表明,红石泉白岗岩具有高SiO2(67.46％ ～75.56％)、富Al2 O3(11.46％ ～14.80％)、贫MgO(0.11％ ～0.99％)、低TFe2O3(0.53％ ～1.10％),铝饱和指数(A/CNK)为0.86～1.12,全碱(ALK)为8.58％ ～10.91％,属于准铝质-弱过铝质碱性花岗岩.白岗岩样品微量元素显示出铀、铷等元素相对富集,磷、钛、钡和铌等元素相对亏损,轻稀土元素(197.79×10-6～15.9×10-6)相对富集,重稀土(32.85×10-6～2.43×10-6)相对亏损,总体Eu负异常.上述地球化学特征均指示红石泉白岗岩具有I型花岗岩特征.综合分析认为,红石泉白岗岩可能形成于后碰撞伸展环境,是由于幔源岩浆底侵作用,提供充足外部热能,致使地壳物质发生部分熔融的产物.

Geochemical Characteristics and Tectonic Significance of Alaskite in Hongshiquan

Hongshiquan area is located in the western part of Longshoushan. This paper makes a detailed petrographic and geochemical analysis of the alaskite to explore its petrogenesis, characteristics of magma source area and tectonic background. The results show that the Hongshiquan alaskite has high SiO2 (67.46% ~ 75.56%), rich Al2O3 (11.46% ~ 14.80%), lean MgO (0.11% ~ 0.99%), low TFe2O3 (0.53% ~ 1.10%), aluminum saturation index (A / CNK) is 0.86 ~ 1.12, and total alkali (ALK) is 8.58% ~ 10.91%, which belongs to quasi aluminum-weak peraluminous alkaline granite. The trace element samples are relatively rich in U, Rb elements, and relatively depleted in P, Nb, Ba, and Ti elements. The rare earth elements are relatively rich in light rare earth (15.9 × 10-6 ~ 197.79 × 10-6), relatively deficient in heavy rare earth (2.43 × 10-6 ~ 32.85 × 10-6), and the overall EU negative anomaly. The above geochemical characteristics indicate that Hongshiquan alaskite has the characteristics of I-type granite. The comprehensive analysis shows that the post-collision extension environment of Hongshiquan alaskite may be due to the magma bottom invasion of mantle-derived magma, which generates a large amount of thermal energy, resulting in partial melting of the crustal material.