乌兰茶卡北山含矿伟晶岩地球化学特征及地质意义

伟晶岩型矿床是稀有金属矿产的主要来源之一，我国西部地区的稀有金属矿床也以伟晶岩型为典型。柴达木盆地北缘乌兰茶卡北山地区岩浆活动频繁，伟晶岩体发育，具有形成稀有金属矿床的良好条件。为了进一步了解伟晶岩的地球化学特征，加深对区域构造演化以及稀有金属成矿和控矿条件的认识，选择该地区含矿伟晶岩作为研究对象，通过分析岩石矿物组合、岩相学特征、主微量及稀土元素组成，解释了侵入古元古界达肯大坂岩群中的伟晶岩地球化学特征。研究发现样品全碱含量较高，这与形成于大陆弧或板块碰撞环境下的成岩特征相似。稀土配分曲线为右倾型，轻重稀土分馏明显，具有Eu中等负异常，推测含矿伟晶岩源区不仅与地壳有关，而且还具有幔源镁铁质岩浆参与的可能性。研究结果表明：研究区内含矿伟晶岩属于亚碱性岩石类型，轻稀土元素富集，重稀土元素亏损，分馏程度较高，反映出在岩浆演化及伟晶岩成岩过程中幔源物质可能参与了稀有稀土金属的成矿作用。研究认为伟晶岩的物质来源不仅与地壳有关，而且还有幔源物质的参与，推断含矿伟晶岩的地质构造环境可能为后碰撞或碰撞后伸展环境。

Geochemical Characteristics and Geological Significance of Ore-bearing Pegmatites in the Wulan Chakabeishan Area

Rare，scattered and rare earth non-ferrous metals is new strategic key mineral resources.At present，some research understandings and breakthroughs have been made in the mineralization and prospecting of key metal deposits in China.Pegmatite type deposit is one of the main sources of rare metal mineral resources，and the rare metal deposits is the most typical of pegmatite types in western China.The magmatic activities are very frequent，and the magmatic rocks are widely distributed，mainly medium-acidic rocks，and very few basite and ultrabasic rock in the Wulan Chakabeishan area of the northern margin of the Qaidam Basin.The main types of rocks with good conditions for forming rare metal deposits，which include syenite granite，monzonitic granite，granodiorite，quartz diorite，tonalite，diorite，gabbro，etc.In order to further understand the geochemical characteristics of the ore-bearing pegmatites in the research area and deepen the understanding of regional tectonic evolution，the mineralization of rare metals and the ore-controlling conditions，the ore-bearing pegmatite was taken as the research object，and the rock mineral features，main trace and rare earth elements composition were analyzed.In the study area，pegmatite vein was band-distributed，outputed in clusters，various types，morphological pulse，beads，lens，and under obvious structural control.The types of pegmatite that closely related to the mineralization of rare metals include mainly muscovite-biotite granite，syenite granite pegmatite，monzonitic granite pegmatite，quartz diorite pegmatite and granodiorite pegmatite.The study found that the ore-bearing pegmatites have high total alkali content，which is similar to the diagenesis characteristics formed in the continental arc or plate collision environment.The partition curve of rare earth is right-leaning，and the light and heavy rare earth fractionation is obvious，and the Eu with medium negative anomaly，it is speculated that the ore-bearing pegmatite source area is not only related to the crust，but also has the possibility of mantle source mafic magma was participated.The results show that the pegmatites were classified and named by the total alkalisili-con （TAS） classification map of the igneous rock system，the samples all fall in the granite-quartz monzonite-syenite area，which belongs to the sub-alkaline rock，and ore-bearing pegmatites have the characteristics of high silicon and overaluminum，and the pegmatites may have experienced the crystallization and separation of mica and feldspar.In this research region，the light rare earth elements is enriched，the heavy rare earth elements is lossed and the fractionation degree is high about ore-bearing pegmatite，it reflects that the mantle source material may be involved in the mineralization of rare metals and rare earth in the magma evolution and diagenetic process of pegmatite.The mineralization is more likely about Rb，Th，Cs，Ce and other rare metal，Ba，Zr，Hf，Nb，Ta，Li and other rare metals have potential for mineralization，and Sr，Y and other rare metals mineralization is little possibility.It is considered that the material source of pegmatites is related to the crust and the participation of mantle source material，and it is inferred that the geological tectonic environment of ore-bearing pegmatites may be post-collision or post-collision extension.The results of the research can provide a theoretical basis for the prospecting of pegmatite type rare metal deposits in the later stage.