【摘要】：研究區(qū)位于陜西省南部,為南秦嶺造山帶的重要組成部分。近年來在安康斷裂南北兩側(cè)分別發(fā)現(xiàn)了兩條鎂鐵—超鎂鐵質(zhì)巖漿雜巖帶,鎂鐵—超鎂鐵質(zhì)巖漿雜巖往往內(nèi)部Fe-Ti礦化特征明顯,賦含大量含Ti-Fe礦物。本論文從巖石學(xué)、巖石地球化學(xué)、礦物化學(xué)和同位素年代學(xué)等方面對安康斷裂南北兩側(cè)鎂鐵—超鎂鐵質(zhì)巖漿雜巖帶進行了系統(tǒng)研究,進而探討Fe-Ti礦化機制,取得的認(rèn)識和成果如下。1、斷裂南北兩側(cè)鎂鐵—超鎂鐵質(zhì)巖漿雜巖帶巖石組成十分復(fù)雜,鎂鐵—超鎂鐵質(zhì)侵入巖類和噴出巖類都有發(fā)育。其中兩側(cè)的噴出巖巖性組合具明顯差異,斷裂北側(cè)的巖石受較強的變形變質(zhì)作用改造,巖性主要為斜長角閃巖、榴閃巖、變質(zhì)凝灰?guī)r;而斷裂南側(cè)基本無變形變質(zhì)作用,巖性以玄武巖、火山碎屑巖為主。兩側(cè)侵入巖巖性組合基本相同,主要為(變)角閃輝石巖、(變)輝石角閃巖、(變)輝長巖、(變)輝綠玢巖和(變)輝綠巖等。2、鎂鐵—超鎂鐵質(zhì)巖漿雜巖的TiO2含量變化較大,可分為成礦鎂鐵—超鎂鐵質(zhì)巖漿雜巖和非成礦鎂鐵—超鎂鐵質(zhì)巖漿雜巖兩種類型。巖石地化顯示成礦鎂鐵—超鎂鐵質(zhì)巖漿雜巖與非成礦鎂鐵—超鎂鐵質(zhì)巖漿雜巖原巖類型存在明顯區(qū)別,成礦鎂鐵—超鎂鐵質(zhì)巖漿雜巖顯示出高堿、高鈦特征,微量元素和稀土元素模式曲線基本類似于典型的OIB模式,輕重稀土分異顯著,具明顯的Eu正異常,非成礦鎂鐵—超鎂鐵質(zhì)巖漿雜巖的微量元素和稀土元素模式曲線則介于E-MORB型玄武巖與洋島玄武巖之間,Eu異常不明顯。3、鎂鐵—超鎂鐵質(zhì)巖漿雜巖的礦物成分主要為角閃石、長石、石榴子石、輝石等,副礦物有鈦鐵礦、榍石等。礦物學(xué)與礦物化學(xué)特征表明,斷裂兩側(cè)含Ti礦物與主要造巖礦物之間的共生組合及結(jié)構(gòu)特征形式多樣且差異明顯,斷裂北側(cè)Ti-Fe氧化物主要為變質(zhì)成因,而南側(cè)Ti-Fe氧化物主要為巖漿后期分異作用形成。此外,研究區(qū)鈦鐵礦具富錳貧鎂的特征與攀枝花、紅格及勉略構(gòu)造帶上已發(fā)現(xiàn)的巖漿型鈦鐵礦床富鎂貧錳的特征正好相反,這與前人對該區(qū)鈦鐵礦成因的認(rèn)識截然不同。4、獲得斷裂北側(cè)變質(zhì)鎂鐵—超鎂鐵質(zhì)巖漿雜巖的LA-ICP-MS鋯石U-Pb諧和年齡為429.5±9.9Ma~447.0±2.5Ma之間,表明其形成于早古生代,即形成晚奧陶紀(jì)—早志留世之間。斷裂南側(cè)鎂鐵—超鎂鐵質(zhì)巖漿雜巖形成時代同為早古生代(421.9±2.0Ma~436.0±4.5Ma),測年結(jié)果表明斷裂兩側(cè)鎂鐵—超鎂鐵質(zhì)巖漿雜巖與研究區(qū)已發(fā)現(xiàn)的含鈦磁鐵礦巖體及近年來北大巴山鎂鐵質(zhì)巖體所測成巖年齡基本上一致,可能為同源、同期巖漿作用的產(chǎn)物。
[Abstract]:The study area is located in the south of Shaanxi Province and is an important part of the South Qinling orogenic belt. In recent years, two mafic-ultra-mafic magmatic complex belts have been found on the north and south sides of Ankang fault. The mafic-ultra-mafic magmatic complex is often characterized by Fe-Ti mineralization and contains a large number of Ti-Fe minerals. In this paper, the mafic-ultra-mafic magmatic complex belt on the north and south sides of Ankang fault is systematically studied from the aspects of petrology, petrogeochemistry, mineral chemistry and isotopic chronology, and then the Fe-Ti mineralization mechanism is discussed. 1. The rock composition of the mafic-ultra-mafic magmatic complex belt on the north and south sides of the fault is very complex, and the mafic-ultra-mafic intrusive rocks and exhaled rocks are developed. The lithologic assemblages of the ejected rocks on both sides are obviously different, and the rocks on the north side of the fault are transformed by strong deformation and metamorphism, and the lithology is mainly plagioclastic hornblende, eclogite and metamorphosed tuff, while there is basically no deformation metamorphism on the south side of the fault, and the lithology is mainly basalt and pyroclastic rock. The lithologic assemblages of the intrusive rocks on both sides are basically the same, mainly including (variable) hornblende, (variable) gabbro, (variable) diabase and (variable) diabase. 2. The TiO2 content of mafic-ultra-mafic magmatic complex varies greatly, which can be divided into two types: ore-forming mafic-ultra-mafic magmatic complex and non-ore-forming mafic-ultra-mafic magmatic complex. The rock geochemistry shows that there is obvious difference between ore-forming mafic-ultra-mafic magmatic complex and non-metallogenic mafic-ultra-mafic magmatic complex. The metallogenic mafic-ultra-mafic magmatic complex shows high alkali and high titanium characteristics, trace elements and rare earth elements model curve is basically similar to the typical OIB model, the differentiation of heavy and heavy rare earth elements is significant, and there is obvious Eu positive anomaly. The trace elements and rare earth element model curves of non-metallogenic mafic-ultra-mafic magmatic complex are between E-MOB basalt and oceanic island basalt, and Eu anomaly is not obvious. 3, the mineral composition of mafic-ultra-mafic magmatic complex is mainly hornblende, feldspar, garnet, pyroxene and so on, and the accessory minerals are ilmenite, sphene and so on. Mineralogical and mineral chemical characteristics show that the symbiotic assemblages and structural characteristics between Ti minerals and main diagenetic minerals on both sides of the fault are diverse and obviously different. The Ti-Fe oxides on the north side of the fault are mainly metamorphosed, while the Ti-Fe oxides on the south side are mainly formed by late magmatic differentiation. In addition, the characteristics of manganese-rich and magnesium-poor ilmenite in the study area are opposite to those of magmatic ilmenite deposits found in Panzhihua, Hongge and Mian structural belts, which is quite different from the previous understanding of the genesis of ilmenite in this area. 4. The LA-ICP-MS zircon U-Pb harmonic age of metamorphosed mafic-ultra-mafic magmatic complex on the north side of the fault is 429.5 鹵9.9 Ma~447.0 鹵2.5Ma. It shows that it was formed in the early Paleozoic, that is, between the late Ordovician and the early Silurian. The formation age of mafic-ultra-mafic magmatic complex on the south side of the fault is the same as that of early Paleozoic (421.9 鹵2.0 Ma~ 436.0 鹵4.5 Ma),). The results show that the magmatic complex on both sides of the fault is basically the same diagenetic age as that of the titanium-bearing magmatic complex found in the study area and the mafic rock mass of North Dabashan in recent years, which may be the product of magmatism at the same time.
【學(xué)位授予單位】：桂林理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.1;P618.31;P618.47

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