粤北塘湾岩体岩石地球化学特征及其意义

Geochemical Characteristic and Significance of Tangwan Granite in North Guangdong

塘湾岩体位于诸广岩体中南部,岩性主要为中细粒斑状二云母花岗岩。对塘湾岩体进行了详细的主量元素、微量元素和稀土元素的研究。结果表明,该岩体表现为高钾钙碱性,SiO_2含量高(72.76%~74.32%,平均值为73.50%),富碱(Na_2O+K_2O=7.61%~8.50%,平均值为8.07%),且钾大于钠,铝过饱和(A/CNK值介于1.03~1.12之间,平均1.07)的特点。微量元素中富集Rb,Th,U,Ce,Zr,Hf,明显亏损Sr,P,Ti,Ta,岩体铀含量较高,Th/U比值低,岩体中的铀多受到了活化改造,对铀成矿有利;稀土元素具有总含量不高,配分模式呈右倾型,轻、重稀土分馏明显,以及强烈的铕负异常等特征。推测其形成于岩石圈伸展减薄的环境下,源区由泥质岩(主要)和砂质岩(次要)混合组成。

Tangwan rock located south Zhuguang rock, its main lithology is fine grained porphyritic two-mica gran- ite. The results show that ： the fine-grained porphyritic two-mica granites of high potassium calc-alkaline, the per- formance of SiO2 content （72.76% ~ 74.32%, with an average of 73.50% ）, rich alkali （Na2O ＋ K20 = 7.61% - 8.50% , with an average of 8.07% ）, and potassium than sodium, aluminum supersaturated （ A / CNK value is betweenl. 03 to 1.12, average 1.07） characteristics. Trace element enrichment of Rb, Th, U, Ce, Zr, Hf, significant loss St, P, Ti, Ta; The uranium content of rock mass is higer;T1CU value is lower; the uranium in rock mass has been activated and transformed, have better potential for uranium production;total REE content is not high, the distribution patterns were rightist type LREE fractionation clear and strong europium negative a- nomalies and other features. Presumably formed in the lower lithospheric extension and thinning of the environ- ment, the source region is composes of argillaceous rock and sand mixture.