对尕尔勤铜矿床花岗闪长斑岩及其锆石的稀土元素进行了分析,并对其成矿作用进行了研究.结果表明,花岗闪长斑岩稀土元素总含量变化范围不大( ΣREE＝48.64 ×10 -6~78.12×10 -6) , LREE/HREE＝8.67 ~11.68,所有样品都呈轻稀土元素相对富集、重稀土元素亏损的右倾型分配模式; δEu由弱负异常→弱正异常演化,这是因为地幔底辟作用引发地壳部分重熔形成长英质岩浆的过程中,逐步消弱了结晶分异导致的负Eu异常进而出现弱的正Eu异常.锆石具有典型的振荡环带,稀土总量较高( ΣREE ＝735.78 ×10 -6~6792.10 × 10 -6) ,相对亏损轻稀土,富集重稀土,正Ce异常明显,并呈现弱的负Eu异常,这是因为在地幔流体作用下,重稀土元素及Ce较其它轻稀土元素更容易进入锆石晶格所致, Eu呈弱的负异常则是成岩后期岩体受氧化淋滤所致.综合分析,揭示出地幔流体作用导致花岗闪长斑岩具有壳幔混染甚至成矿特征,同时还能透过岩浆与围岩发生物质和能量的交换,导致变质砂岩成矿的成因机制.%The rare earth elements (REEs) in granodiorite porphyry and zircon from the Gaerqin copper deposit of Tibet, China, were geochemically traced, and the mineralization was also studied.The total levels of REEs in granodiorite porphyry varied slightly ( ΣREE＝48.64 ×10 -6~78.12 ×10 -6) with LREE/HREE＝8.67~11.68.All samples were featured by a right-leaning distribution with enrichment in light REEs ( LREEs) and depletion in heavy REEs ( HREEs), δEu changed from weak negative anomaly to weak positive anomaly, which is due to the gradual weakening of negative Eu anomalies caused by crystallization differentiation and a weak positive Eu anomaly in the process of the partially remelting growth of the angled magma in the crust.The zircon was found with typical oscillatory zones, large total REE levels ( ΣREE ＝735.78 ×10 -6~6792.10 ×10 -6), LREE depletion, HREE enrichment, evident Ce positive anomaly and weak negative Eu anomaly.This is because under the action of mantle fluid, heavy rare earth elements and Ce are more likely to enter the lattice of zircon than other light rare-earth elements.The weak negative abnormality of Eu is caused by oxidation and leaching of the late diagenetic rock mass.Comprehensive analysis reveals that the mantle fluid action endowed the granodiorite porphyry with the characteristics of crust-mantle mixing or even ore-formation.Meanwhile, the matter-energy exchange between magma and surrounding rocks accounted for the metamorphic sandstone ore-formation.
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