青藏高原那日尼亚地区新近纪查保玛组火山岩岩石地球化学特征

Volcanic Rock Geochemistry of Neogene Check Baoma Formation in Nariniya Area,Qinghai-Tibetan Plateau

那日尼亚地区铅锌矿主要位于新近纪火山岩中,成矿的层控型明显,查保玛组火山岩是最主要的含矿层位之一。对地球化学特征研究表明,该组火山岩为一套钙碱性-碱性系列的中酸性岩石组合,以富碱高钾含量为特征。稀土配分模式高度分异,轻重稀土元素分馏明显。δEu为0.73～0.97,无明显负Eu异常。微量元素的配分模式近似一致,相对于原始地幔,富集大离子亲石元素(K、Ba、Rb、Sr)和Th、U等活泼的不相容元素,而Zr、Ti、Ta、P等高场强元素则相对亏损。Rb/Sr为0.07～0.27,Rb/Sr值为0.07～0.27,显示壳幔混合特点。岩石可能源于EMⅡ型富集地幔含金云母的地幔橄榄岩的部分熔融,经过分离结晶的岩浆房富钾岩浆沿构造薄弱部位上侵,与地壳物质发生混合形成混合岩浆,在地壳浅部就位。微量元素中具有高的铅锌背景值,为成矿提供主要物质来源。在R1-R2构造判别图解上,样品主要落入碰撞后伸展和后碰撞环境。结合区域构造背景分析,该套火山岩形成于陆内伸展构造背景。

Nariniya Pb-Zn deposits is located mainly in the Neogene volcanic rock, with obvious metallogenic layer control type. Zhabaoma group volcanic rock is one of the main ore-bearing horizons. The geochemical characteristics of the Nariniya group volcanic rocks were researched in this work. The result shows that the volcanic rock is a set of calcium alkalinealkaline series of acidic rock assemblages with a rich alkali high potassium content. Rare earth distribution pattern is different, the light and heavy rare earth element distilled obviously. δEu is between 0. 73 and 0.97, and there is no obvious negative europium anomaly. Trace element distribution mode is approximately consistent, for the original mantle, big ion lithophile elements （K, Ba, Rb, Sr） and Th, U etc lively incompatible elements are enriched and Zr, Ti, Ta, P high field strength elements are relatively less. Rb/Sr is 0. 07-0.27, Rb/Sr ratio is 0. 07-0.27, which shows the crust-mantle mixing characteristics. The rock may be from EM II type enrichment mantlegold bearing mica mantle peridotite of partial melting, crystallization after the separation of the magma chamber rich potassium magma along the tectonic weak part in invasion, and crustal material produce mixed form mixed magma in the earth＇s crust shallow in place. Trace elements have high lead and zinc background value, for providing main ore-forming material sources. In the R1, R2 structure discrimination diagrams, sample mainly fall into the impact after the stretch and after collision environment. In the R1, R2 structure discrimination diagrams, sample mainly fall into the impact after the stretch and after collision environment grams, sample mainly fall into the impact after the stretch and after collision environment.