本文選題：成礦作用 + 流體包裹體��； 參考：《中國地質(zhì)科學院》2015年碩士論文

【摘要】：八大關(guān)斑巖Cu-Mo礦床是我國內(nèi)蒙大興安嶺成礦帶北段典型的斑巖型Cu-Mo礦床之一,地處中亞造山帶東段,額爾古納地塊內(nèi)嵯崗-得爾布爾隆起區(qū)。礦體主要產(chǎn)出在印支期花崗閃長斑巖體內(nèi)和巖體的接觸帶,主體呈脈狀展布。礦床具有典型的斑巖型銅礦蝕變分帶現(xiàn)象,從巖體中心向外依次發(fā)育鉀化帶→石英-絹云母化帶→絹云母花帶→青磐巖化帶,蝕變與礦化關(guān)系密切。礦化以銅鉬礦化為主,輝鉬礦主要伴隨石英脈產(chǎn)出,以脈狀分布為主,主要分布在石英-絹云母化帶；黃銅礦主要呈浸染狀、細脈浸染狀分布,與絹云母化帶關(guān)系密切,少數(shù)分布在石英-絹云母花帶。 本文對礦區(qū)主要侵入巖的巖相學、成巖成礦時代和成礦流體特征進行了查明,較以往工作進行了更加系統(tǒng)的研究。鏡下鑒定結(jié)果顯示礦區(qū)侵入巖巖性主要有黑云母花崗巖、花崗巖、鉀長花崗巖、花崗斑巖、花崗閃長斑巖等；LA-MS-ICP-MS鋯石U-Pb定年結(jié)果顯示,礦區(qū)主要侵入巖集中分布在(243～237Ma)和(231～229Ma)兩個階段,均與印支期構(gòu)造-巖漿活動密切相關(guān)。此外,獲得輝鉬礦Re-Os等時線年齡為228.7±3.1Ma,與成礦花崗閃長斑巖的就位年齡(230.5Ma)在誤差范圍內(nèi)基本一致,說明八大關(guān)成礦事件發(fā)生在中三疊世,與印支晚期構(gòu)造-巖漿活動有關(guān)。 礦區(qū)侵入巖地球化學研究表明,礦區(qū)印支期侵入巖總體上表現(xiàn)為高SiO2和富A1203,低MgO和TFe2O3,富集LREE、LILE和虧損HREE、HFSE,弱的Eu負異常,顯示具有俯沖環(huán)境島弧花崗巖的特征。結(jié)合礦區(qū)侵入巖鋯石的Hf同位素研究,表明礦區(qū)印支期侵入巖的初始巖漿起源于新元古代早期由虧損地幔派生的新生年輕地殼的部分熔融,在MASH區(qū)加入了少量的古老地殼的。 流體包裹體研究表明,八大關(guān)銅鉬礦床流體包裹體類型豐富,有V型富氣相包裹體、L型富液相包裹體、S型含子礦物多相包裹體,C型含CO2的三相包裹體。成礦流體演化過程具有早、中、晚三階段的特點,其均一溫度主要集中在238℃～572℃,鹽度集中在0.42～63.13%NaCleqv,反映了巖漿熱液的特點。銅鉬金屬元素的沉淀主要發(fā)生在中階段,但其沉淀機制卻發(fā)生了解耦,輝鉬礦的大量沉淀主要與減壓沸騰作用有關(guān),黃銅礦的沉淀主要與溫度降低有關(guān)。 巖相學研究和激光拉曼分析表明,成礦流體早中階段流體包裹體除H2O外,還含CO2和少量N2；子晶可見石鹽、硬石膏、赤鐵礦和硫化物；晚階段石英脈包裹體只含H2O,無CO2和子晶。成礦流體由早中階段的H20-NaCl-CO2體系逐漸向晚階段的H2O-NaCl體系演化。H-O-S同位素分析結(jié)果均表明,成礦流體主要來源于巖漿熱液,大氣水的混合比例有限；成礦物質(zhì)主要來自地幔,并有少量圍巖中S的參與。 在印支期,研究區(qū)主要處于鄂霍茨克洋朝南向中蒙聯(lián)合板塊俯沖、碰撞的構(gòu)造背景。結(jié)合侵入巖的地球化學特征和Hf同位素分析結(jié)果,本文認為八大關(guān)銅鉬礦床形成于印支晚期鄂霍茨克洋俯沖向陸陸碰撞轉(zhuǎn)換的構(gòu)造環(huán)境,而區(qū)域規(guī)模的動力變形變質(zhì)作用暗示蒙古鄂霍茨克洋在額爾古納地區(qū)的的閉合時間可能在印支晚期。
[Abstract]:The Ba Da Guan porphyry Cu-Mo deposit is one of the typical porphyry type Cu-Mo deposits in the northern part of the Greater Khingan Range metallogenic belt in Inner Mongolia. It is located in the eastern part of the Central Asian orogenic belt and in the Eergu'Na block. The ore body is mainly produced in the contact zone of the granodiorite porphyry and rock mass in the Indosinian period, and the main body is in the vein. The deposit is typical of the deposit. The alteration zoning phenomenon of porphyry copper deposits has developed from the center of the rock mass to the potash zone, quartz sericite belt, sericite flower belt and green pan rock zone. The alteration and mineralization are closely related to mineralization. The mineralization is mainly copper molybdenum mineralization. The molybdenite is mainly accompanied by quartz veins, mainly in the vein distribution, mainly in the quartz sericite zone; Copper deposits are mainly disseminated, veined disseminated and closely related to sericite zones, and a few are distributed in quartz sericite belts.
In this paper, the petrography of the main intrusive rocks, the age of diagenesis and mineralization and the characteristics of the ore-forming fluid have been identified, and more systematic studies have been carried out than previous work. The results of microscopic identification show that the lithology of the intrusive rocks in the mining area mainly include the black mica granite, granite, potassium feldspar, granite porphyry, granite diorite porphyry, and so on, and LA-MS-ICP-MS zircon U The -Pb dating results show that the main intrusive rocks in the mining area are concentrated in (243 to 237Ma) and (231 to 229Ma), which are closely related to the Indosinian tectonic magmatism. In addition, the Re-Os isochronous age of the molybdenite is 228.7 + 3.1Ma, which is basically the same as that of the ore-forming granodiorite in the range of error (230.5Ma). The Guan Cheng mine occurred in the middle three Permian, which is related to the tectono magmatic activity in the late Indo China.
The geochemical study of intrusive rocks in the mining area shows that the Indosinian intrusive rocks in the mining area were generally high SiO2 and rich A1203, low MgO and TFe2O3, enriched LREE, LILE and defective HREE, HFSE, and weak Eu negative anomalies, showing the characteristics of the subducted island arc granite. The Hf isotopes of zircon from the intrusive rocks in the mining area indicate that the Indosinian intrusive rocks in the mining area were shown. The initial magma originated from partial melting of new young crust derived from depleted mantle in the early Neoproterozoic, and a small amount of ancient crust was added to the MASH area.
Fluid inclusion studies show that the fluid inclusions in the Ba Da Guan copper molybdenum deposit are rich in fluid inclusions, including V rich gas inclusions, L rich liquid inclusions, S type mineral inclusions and C type CO2 containing three phase inclusions. The evolution process of the ore-forming fluid has the characteristics of early, middle and late three stages, and the homogenization temperature is mainly concentrated at 238 to 572 degrees C, and salinity is mainly concentrated. The concentration of 0.42 ~ 63.13%NaCleqv reflects the characteristics of magmatic hydrothermal solution. The precipitation of copper and molybdenum metal elements occurs mainly in the middle stage, but the precipitation mechanism has been decoupled. The precipitation of molybdenite is mainly related to the effect of decompression and boiling, and the precipitation of chalcopyrite is mainly related to the temperature reduction.
Petrographic study and laser Raman analysis show that the fluid inclusions in the early and middle stage of the ore-forming fluid contain CO2 and a small amount of N2 except for H2O, and the subcrystals can be seen as stone salt, anhydrite, hematite and sulfide, and the late phase quartz vein inclusions only contain H2O, without CO2 and subcrystal. The metallogenic fluid is gradually from the H20-NaCl-CO2 system of the early middle stage to the H2O-NaCl in the late stage. The results of.H-O-S isotope analysis show that the ore-forming fluids are mainly derived from magmatic hydrothermal fluid, and the mixing ratio of atmospheric water is limited; the metallogenic material mainly comes from the mantle and has the participation of S in a small number of surrounding rocks.
During the Indosinian period, the study area was mainly in the subduction of the Sino Mongolia joint plate in the south of Okhotsk ocean and the tectonic setting of the collision. Combined with the geochemical characteristics of the intrusive rocks and the results of Hf isotope analysis, this paper holds that the Ba Da Guan copper molybdenum deposit formed in the tectonic setting of the transition from the subduction of the late Indo to the Okhotsk ocean to the continental collision, and the regional scale. Dynamic deformation and metamorphism suggest that the closure time of Mongolia Okhotsk ocean in Eergu'Na area may be in the late Indosinian period.
【學位授予單位】：中國地質(zhì)科學院
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P618.41;P618.65

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