【摘要】：龍陵縣象達(dá)-平達(dá)地區(qū)位于滇西古特提斯構(gòu)造域的東段,是岡瓦納大陸與歐亞陸塊南緣相碰撞的結(jié)合部,對(duì)研究古特提斯造山作用和尋找有色金屬礦產(chǎn)有重要意義。本文以出露于象達(dá)-平達(dá)地區(qū)的中-新生代花崗巖為研究主體,對(duì)其巖石學(xué)、地球化學(xué)特征進(jìn)行比較細(xì)致的研究,結(jié)合巖石年代學(xué)、區(qū)域地質(zhì)學(xué)、巖石大地構(gòu)造學(xué)等方面的研究探討花崗巖的成因與構(gòu)造環(huán)境,獲得的主要結(jié)論概括如下：(1)研究區(qū)出露的中-新生代花崗巖主要有三期：分布在象達(dá)鄉(xiāng)的侏羅紀(jì)花崗巖；分布在象達(dá)東邊和平達(dá)鄉(xiāng)兩側(cè)的白堊紀(jì)花崗巖；分布在勐堆北部地區(qū)的古近紀(jì)花崗巖。(2)三期花崗巖均具有“富鋁-鈉、高鎂-鉀”的特點(diǎn)。屬?gòu)?qiáng)過(guò)鋁花崗巖,具有高鉀鈣堿性巖的特點(diǎn)；稀土元素總量較高；輕、重稀土元素的分餾較為強(qiáng)烈。侏羅紀(jì)花崗巖與張旗等(2006)所稱的高Sr低Yb花崗巖(埃達(dá)克巖)相同；而白堊紀(jì)和古近紀(jì)花崗巖在Sr-Yb圖解中落入低Sr低Yb到極低Sr高Yb花崗巖區(qū)。(3)三期花崗巖主要落在Pearce (1994)重新定義的Post-COLG(即后碰撞花崗巖),與Hf-Rb-Ta圖解的投影結(jié)論較吻合。(4)侏羅紀(jì)花崗巖具有鉀質(zhì)C型埃達(dá)克巖特征,可能形成于加厚地殼開始減薄及地殼從擠壓向拉張伸展轉(zhuǎn)換的環(huán)境；為下地殼內(nèi)的底侵玄武巖在榴輝巖相的部分熔融產(chǎn)物；白堊紀(jì)和古近紀(jì)花崗巖可能是在正常地殼厚度下差異性深度上的部分熔融產(chǎn)生的,也可能是區(qū)域拉張環(huán)境下的減薄地殼部分熔融的產(chǎn)物。(5)結(jié)合近年來(lái)完成的地質(zhì)資料分析,怒江-昌寧-孟連結(jié)合帶以西廣泛出露的晚中生代花崗巖總體上具有連續(xù)演化的趨勢(shì),特別是在Sr-Yb圖解中表現(xiàn)更為清晰：蚌渺巖體屬高Sr低Yb型花崗巖,騰沖微地塊東緣的中侏羅世花崗巖主要為低Sr低Yb型花崗巖,早白堊世花崗巖的低Sr高Yb型花崗巖,晚白堊世花崗巖主要屬極低Sr高Yb型花崗巖,少數(shù)為低Sr高Yb型；可能反映了后碰撞→后造山構(gòu)造背景的演化過(guò)程中巖漿源區(qū)逐漸向上遷移、壓力環(huán)境逐漸降低的過(guò)程。
[Abstract]:The Xiangda-Pingda area of Longling County is located in the eastern part of the PaleoTethys tectonic domain in western Yunnan. It is the confluence of the southern margin of Gondwana continent and Eurasian continental block, which is of great significance to the study of the Paleotesian orogeny and the exploration of non-ferrous metal minerals. In this paper, the Mesozoic and Cenozoic granites exposed in Xiangda Pingda area are taken as the main body of study. The petrology and geochemistry of granites are studied in detail, combined with petrochronology and regional geology. The main conclusions are summarized as follows: (1) the Meso-Cenozoic granites in the study area mainly have three periods: Jurassic granites distributed in Xiangda Township; Cretaceous granites distributed in the east of Xiangda and Pingda Township, and Paleogene granites in northern Mengdui. (2) the third stage granites have the characteristics of "rich aluminum-sodium and high magnesia-potassium". It is a strong peraluminous granite with the characteristics of high potassium calc-alkaline rock, high rare earth elements and strong fractionation of light and heavy rare earth elements. Jurassic granite is the same as Zhangqi et al. (2006) called high Sr low Yb granite (Adakite); The Cretaceous and Paleogene granites fell into the low Sr low Yb to very low Sr high Yb granite areas in the Sr-Yb diagram. (3) the third stage granites mainly fall in the Post-COLG (post-collision granite) redefined by Pearce (1994), which is consistent with the projection results of the Hf-Rb-Ta diagram. (4) Jurassic granites are characterized by K-C type adakite. It may be formed in the environment where the thickened crust begins to thinning and the crust is transformed from compression to extensional extension, which is the partial melting product of the underthrust basalt in the lower crust in the eclogite facies. The Cretaceous and Paleogene granites may have resulted from partial melting at different depths under normal crustal thickness, or may be the product of partial melting of thinned crust in a regional extensional environment. (5) Analysis of geological data completed in recent years. The late Mesozoic granites, widely exposed to the west of the Nujiang Changning Menglian junction belt, have a general trend of continuous evolution, especially in the Sr-Yb diagram. The oysterian granites belong to high Sr low Yb type granites. The middle Jurassic granites in the eastern margin of the Tengchong microblock are mainly low Sr low Yb type granites, the early Cretaceous granites are low Sr high Yb type granites, the late Cretaceous granites are mainly very low Sr high Yb type granites, and a few are low Sr high Yb type granites. It may reflect the gradual upward migration of magmatic source region and the decrease of pressure environment during the evolution of post-collision and post-collision orogenic tectonic setting.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.121

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本文編號(hào)：2220670