本文選題：南秦嶺 + 花崗(斑)巖　； 參考：《西北大學(xué)》2015年碩士論文

【摘要】：在南秦嶺柞水-山陽地區(qū)廣泛分布著一系列的小型中酸性花崗(斑)巖體,這些花崗(斑)巖體通常伴隨著普遍的礦化作用。本文通過對這些中酸性的成礦小花崗(斑)巖體進(jìn)行野外地質(zhì)、巖相學(xué)、LA-ICP-MS鋯石U-Pb年代學(xué)、地球化學(xué)等方面的綜合研究,分析探討巖石的成因類型、礦物組成、形成時(shí)代、巖漿源區(qū)、構(gòu)造演化及地球動(dòng)力學(xué)背景,得到了如下認(rèn)識與成果：中酸性花崗(斑)巖體類型主要包括花崗閃長(斑)巖、二長花崗(斑)巖、石英閃長巖和閃長(玢)巖等。巖石中礦物組成主要為鉀長石、斜長石、石英和暗色礦物角閃石、黑云母等,副礦物包括鋯石、磷灰石、榍石和磁鐵礦等。LA-ICP-MS鋯石U-Pb定年顯示,它們的加權(quán)平均年齡分別為：下官坊花崗閃長(斑)巖(146.78±0.91Ma)；園子街二長花崗(斑)巖(145.56±0.95Ma)；袁家溝二長花崗巖(143.67±0.90Ma)；小河口二長花崗巖(142.34±0.92Ma)；白沙溝石英閃長巖(141.09±0.72Ma)；池溝石英閃長巖(141.5±1.0Ma)；土地溝二長花崗(斑)巖(139.29±0.90Ma),這些年齡代表了巖體形成于晚侏羅-早白堊世。地球化學(xué)特征顯示,此地區(qū)巖體具有高硅(SiO2=60.19～69.20 wt.%)、富堿(K2O+Na2O=7.00-10.21 wt.%)、高鋁(Al2O3=15.03～15.91 wt.%)、低鈣(CaO=1.34～4.54 wt.%)的特征,A/CNK=0.82-1.12(平均為0.92),反應(yīng)巖石以具準(zhǔn)鋁質(zhì)到過鋁質(zhì)特征的高鉀鈣堿性巖為主。巖石稀土元素具有輕稀土富集(LREE=103.80～191.95ppm)、重稀土虧損(HREE=8.05～15.04 ppm),稀土元素分異明顯(LREE/HREE=10.83～14.89、 (La/Yb)N=12.35～21.06),銪異常不明顯(δEu=0.89-1.10)的特點(diǎn)。微量元素蛛網(wǎng)圖顯示巖石總體具有虧損Nb、Ta、Ti、P等高場強(qiáng)元素(HFSE),富集K、Rb、Sr、Ba、 Pb等大離子親石元素(LILE)的特點(diǎn)。結(jié)合巖體的野外地質(zhì)、巖相學(xué)、年代學(xué)和地球化學(xué)特征,可以得出本區(qū)巖體屬于Ⅰ型花崗巖,并具有相似的巖漿源區(qū),巖漿可能主要來自古老地殼的重熔以及少量殼�；旌稀r體應(yīng)形成于擠壓背景之下,擠壓使得地殼加厚,加厚地殼發(fā)生熔融,進(jìn)而產(chǎn)生了這些小型的花崗質(zhì)巖體。
[Abstract]:A series of small intermediate-acid granitic (porphyry) bodies are widely distributed in the area of tussah-Shanyang, South Qinling. These granitic (macular) rocks are usually accompanied by widespread mineralization. In this paper, through the comprehensive study of field geology, lithofacies, U-Pb geochronology and geochemistry of these intermediate-acid ore-forming Xiaohuagang (porphyry) intrusions, the genetic types, mineral composition and forming age of the rocks are analyzed and discussed. In the magmatic source area, tectonic evolution and geodynamic background, the following results have been obtained: the types of intermediate-acid granodiorite (porphyry) include granodiorite (porphyry), erchang granodiorite (porphyry), quartz diorite and diorite (porphyry). The mineral composition of the rocks is mainly composed of potash feldspar, plagioclase, quartz and dark mineral hornblende, biotite, etc. The secondary minerals include zircon, apatite, sphene and magnetite, etc. The zircon U-Pb dating shows that Their weighted average ages are: Xiaguanfang granodiorite (porphyry) 146.78 鹵0.91MaA; Yuanzijie Erchang granodiorite (porphyry) 145.56 鹵0.95MaA; Yuanjiagou monzogranite 143.67 鹵0.90 Mai; Xiaohekou Erchangite 142.34 鹵0.92MaMa; Baishagou quartz diorite 141.09 鹵0.72MaA; Zigou quartz diorite 141.09 鹵0.72MaA; Yuanjiagou monzogranite 143.67 鹵0.90 Mai; Xiaoguanfang granite 142.34 鹵0.92MaA; Baishagou quartz diorite 141.09 鹵0.72MaA These ages represent the late Jurassic-early Cretaceous formation of the rock mass, 141.5 鹵1.0 Ma ~ (-1) and 139.29 鹵0.90 Ma ~ (-1) of the earlong granitic (porphyry) rocks. The geochemical characteristics show that the rock bodies in this area have the characteristics of high SiO2 + 60.19 ~ 69.20 wt., alkali-rich K _ 2O Na2O=7.00-10.21 wt., high Al _ 2O _ 3O _ 3 15.03 ~ 15.91 wt.T, low Ca _ 2O _ (1.34) ~ 4.54 wt.12 (average = 0.92), and the reactive rocks are mainly high-potassium calc-alkaline rocks with the characteristics of quasi-aluminous to peraluminous. The rare earth elements in rocks are characterized by LREE _ (103.80) ~ (191.95) ppm ~ (-1), HREE ~ (8.05) ~ 15.04 ppm ~ (-1), LREE / HREE ~ (10.83) ~ 14.89, La / Y _ (B) N _ (12.3521.06), EU ~ (3 +) anomaly (未 EU ~ (0.89-1.10). The trace element cobweb diagram shows that the rocks are characterized by depletion of high field strength elements such as NbTa-TIAP and enrichment of large ion lithophile elements such as K ~ (B) ~ (b) ~ (2 +) Sr ~ (2 +) Ba, Pb (LILE). Combined with the field geology, petrography, geochronology and geochemistry of the rock mass, it can be concluded that the rock body in this area belongs to type I granite and has similar magmatic source. The magma may mainly come from the remelting of the ancient crust and a small amount of crust-mantle mixing. The rock mass should be formed in a compressional background, which makes the crust thicker and thickens the crust to melt, thus producing these small granitic rocks.
【學(xué)位授予單位】：西北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121

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