【摘要】：斑巖型鉬礦床的最大特點(diǎn)是品位較低,但成礦規(guī)模較大,其中的輝鉬礦主要呈細(xì)脈狀或者浸染狀賦存于中、酸性的含礦巖體中。其資源量和工業(yè)利用量在全球總儲(chǔ)量和總利用量中的地位是極其重要的。近年來,青海省地質(zhì)調(diào)查研究院在東昆侖造山帶拉陵灶火中游一帶發(fā)現(xiàn)了典型的斑巖型鉬多金屬礦床,而在該礦區(qū)的東南方向亦發(fā)現(xiàn)了鉬礦化蝕變,隨即環(huán)繞該區(qū)出露的博武斑巖體展開研究工作,此次研究區(qū)內(nèi)的巖石組合系統(tǒng)可劃分三大類:為花崗斑巖類、閃長(zhǎng)巖類、變質(zhì)巖類。含礦巖體主要斑狀正長(zhǎng)花崗巖與多斑斑狀花崗巖,輝鉬礦呈細(xì)脈浸染狀賦存在其中。斑狀正長(zhǎng)花崗巖與多斑斑狀花崗巖的地球化學(xué)特征顯示其為一套弱過鋁質(zhì)的高鉀鈣堿性花崗巖,是由于同碰撞作用導(dǎo)致的加厚地殼上部重新熔融而形成S型花崗巖。而灰黑色花崗斑巖則為一套鈣堿性花崗巖,該花崗巖組構(gòu)及物質(zhì)來源與含礦巖體明顯不同;灰黑色花崗斑巖Nb/Ta平均值13.07×10-6,其中最大值為15.26×10-6,Rb/Sr值H9樣品為0.19×10-6、H11為0.22×10-6比值介于地幔比值地殼比值之間,Zr/Hf比值遠(yuǎn)遠(yuǎn)低于地幔源巖石的Zr/Hf比值,其總體特征顯示了與含礦巖體的不同。斑狀正長(zhǎng)花崗巖與多斑斑狀花崗巖為博武巖體斑巖型鉬礦的含礦巖體,是陸陸碰撞環(huán)境下熔融了地殼而形成的S型高鉀鈣堿性花崗巖,兩者的地球化學(xué)、鋯石U-Pb年齡等特征相似,為同源演化,其結(jié)構(gòu)的不同主要是由于在巖漿房中所賦存位置的不同而形成在。LA-ICP-MS鋯石U-Pb測(cè)年所獲得的加權(quán)平均年齡分別為216.1±3.0Ma、216.1±2.4Ma。博武巖體斑巖型鉬礦形成的碰撞時(shí)期是在晚三疊世卡尼階,大約在222Ma左右。區(qū)內(nèi)共發(fā)生了兩次成礦作用,一次是同碰撞成礦作用,即碰撞過程中由于俯沖板片斷離誘發(fā)的拆沉作用,這一期次形成的輝鉬礦以浸染狀形式存在于巖體中,推測(cè)形成年齡為222Ma;第二次后碰撞成礦作用,即巖石圈的拆沉作用導(dǎo)致,這一期次形成的輝鉬礦以含輝鉬礦石英的脈形式存在于巖體中,兩期成礦作用均為透巖漿流體成礦作用。經(jīng)此次研究工作,最終認(rèn)為博武斑巖型鉬礦在礦床類型上屬于深成侵入體型斑巖鉬礦,且經(jīng)歷了兩次輝鉬礦的積淀過程,找礦潛力巨大。
[Abstract]:The porphyry molybdenum deposit is characterized by its low grade but large metallogenic scale, in which molybdenum occurs mainly in the form of veinaceous or disseminated ore bodies and acidic ore-bearing rocks. The status of resources and industrial utilization in the global total reserves and total utilization is extremely important. In recent years, the Qinghai Provincial Geological Survey Institute has found typical porphyry molybdenum polymetallic deposits in the middle reaches of the Laling Zaohuo Orogen of the East Kunlun orogenic belt, and molybdenum mineralization and alteration have also been found in the southeast direction of the ore area. The rock assemblage system in this study area can be divided into three categories: granitic porphyry diorite metamorphic rock. The ore-bearing bodies are mainly porphyry syenite and polyporphyritic granites, in which molybdenum occurs in the form of veinlet dipping. The geochemical characteristics of porphyry syenite and polyporphyritic granites show that they are a set of weak peraluminous calc-alkaline granites, which formed S-type granites due to the remelting of the upper part of the thickened crust caused by the simultaneous collision. The gray-black granitic porphyry is a set of calc-alkaline granite, the fabric and material source of the granite is obviously different from the ore-bearing rock mass. The average Nb/Ta value of gray-black granitic porphyry is 13.07 脳 10 ~ (-6), in which the maximum value is 15.26 脳 10 ~ (-6) Rb / Sr value H _ 9 sample is 0.19 脳 10 ~ (-6) H _ (11) ratio is 0.22 脳 10 ~ (-6) ratio is between mantle ratio crust ratio and Zr/Hf ratio of mantle source rock, its general characteristics show that it is different from ore-bearing rock body. Porphyry syenite and polyporphyry granites are ore-bearing bodies of porphyry molybdenum deposits in Bowu pluton. They are S-type high-potassium calc-alkaline granites formed by melting the crust in continental collision environment. The U-Pb age of zircon is similar, which is homologous evolution. The difference in structure is mainly due to the different location of zircon in magma chamber. The weighted mean age obtained by U-Pb dating of zircon from LA-ICP-MS is 216.1 鹵3.0 Ma ~ 216.1 鹵2.4 Ma. respectively. The collision period of porphyry molybdenum deposit in Bowu pluton occurred in the late Triassic Carney stage, about 222Ma. There are two metallogenic processes in the area, one of which is syncollision mineralization, that is, during the collision, the molybdenum ore formed in this stage exists in the rock mass in the form of dipping, which is caused by the detachment of subduction plate. It is assumed that the age of formation is 222Ma.The second post-collision mineralization, that is, the desilting of lithosphere, resulted in molybdenum deposit in the form of molybdenum bearing quartz vein in the rock mass, and the mineralization in both stages is permeable magmatic fluid mineralization. Through this research work, it is concluded that Bowu porphyry molybdenum deposit belongs to deep intrusive porphyry molybdenum ore deposit type, and has experienced two molybdenum deposit accumulation process, and the prospecting potential is great.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P618.65

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