滇东南薄竹山花岗岩岩石学及其稀土-微量元素地球化学

薄竹山花岗岩体分两期侵入,第一期岩石类型主要为中粒黑云母二长花岗岩,SiO_2含量介于64.82%～72.01%,平均68.72%,总碱度K_2O+Na_2O=5.51%～8.2%,平均6.92%,A/CNK平均1.14,富集Rb、U、Th等微量元素和轻稀土元素,中等的Eu负异常,δEu=0.37～0.55,属过铝质花岗岩,主要形成于同碰撞阶段;第二期主要为细粒二长花岗岩,SiO_2含量变化范围75.94%～76.89%,平均76.33%,总碱度K_2O+Na_2O=7.58%～8.82%,平均8.22%,A/CNK.A/NK图上主要落在准铝质范围,微量元素Nb、Ta、Y富集,显著亏损Sr、Ba,强烈的Eu负异常,δEu=0.06～0.11,形成于板内的伸展环境.第二期花岗岩Ba、Sr亏损明显,这与强烈的Eu负异常相对应,说明第二期花岗岩经历了高度演化.

Petrology and REE-Trace Element Geochemistry of Bozhushan Granite Pluton in Southeastern Yunnan Province, China

Bozhushan granite comprises two intrusive bodies. The first intrusion is dominated by medium grained bio-tite monzogranite. Their SiO_2 and total alkaline contents are in the ranges of 64. 82% -72. 01% (average 68. 72% ) and 5.51% -8. 2% (average 6.92% ) , respectively. The rocks display positive Rb, U, Th, and LREE, and medi-um strong negative Eu anomalies (δEu = 0. 37 - 0. 55). Most of rocks belong to peraluminous( average A/CNK =1. 14) granite and generated in syn-collisional setting. The second intrusion mainly consists of fine grained monzogranite, most of which belongs to metaluminous rocks and is characterized by high SiO_2(75.94% -76. 89% )and total alkaline (7. 58% -8. 82% ). These rocks are enriched in Nb, Ta, Y, and significant depleted in Sr, Ba,and Eu ( δEu = 0. 06 - 0. 11). This intrusion is formed in an extensional setting. Compared with the first intrusion, the second is mostiy depleted in Ba, Sr, and Eu, indicating the higher evolvement.