本文選題：晚石炭世　切入點(diǎn)：堿長花崗巖　出處：《石家莊經(jīng)濟(jì)學(xué)院》2015年碩士論文

【摘要】：研究區(qū)位于內(nèi)蒙古蘇尼特左旗地區(qū)西北部,大地構(gòu)造位置屬中亞造山帶東段—興蒙造山帶。該區(qū)構(gòu)造單元劃分屬興蒙造山帶北方造山帶,南側(cè)以二連—賀根山斷裂帶為界,北側(cè)屬西伯利亞活動大陸邊緣,查干敖包—阿榮旗深斷裂東西向穿過該區(qū)。該區(qū)古生代屬于古亞洲洋構(gòu)造域,進(jìn)入中生代,則屬濱西太平洋構(gòu)造域。研究區(qū)出露地層包括石炭系寶力高廟組一段碎屑巖、白堊系白音高老組火山巖、白堊系大磨拐河組、古近系伊爾丁曼哈組及第四系。堿長花崗巖巖體周緣被白音高老組火山巖噴發(fā)不整合覆蓋。研究區(qū)花崗巖類巖石組合主要為堿長花崗巖、二長花崗巖和花崗閃長巖。本文主要研究了堿長花崗巖體。堿長花崗巖基出露于查干敖包—阿榮旗斷裂以北準(zhǔn)和熱音蘇木一帶,在楚圖陶勒蓋一帶被斑狀花崗閃長巖侵入。堿長花崗巖體發(fā)育發(fā)育東西向展布的斑狀花崗閃長巖脈和斑狀黑云母二長花崗巖脈。堿長花崗巖的鋯石U-Pb同位素測年獲得206Pb/U238加權(quán)平均年齡為312.2Ma±7.4Ma(MSWD=6.67),屬于晚石炭世。地球化學(xué)分析結(jié)果顯示,堿長花崗巖高硅、富堿,顯示鈣堿性巖漿地球化學(xué)特征;A/CNK=1.01~1.12,A/NK=1.05~1.40,屬于準(zhǔn)鋁質(zhì)-弱過鋁質(zhì)巖石。堿長花崗巖輕重稀土分餾不明顯,具有明顯的Eu負(fù)異常,呈典型的“海鷗型稀土配分曲線”。在原始地幔標(biāo)準(zhǔn)化微量元素蛛網(wǎng)圖上,堿長花崗巖不相容元素Ba、Nb、Ce、Sr、Ti虧損明顯,相容元素Rb、U、Th等富集,表明地殼巖漿源區(qū)特征。堿長花崗巖高10000Ga/Al比值和高Zn、Zr、Y、Ce含量,在花崗巖分類圖解上分布于A型花崗巖區(qū)。它們高Ga和Y、低Nb,屬于A2-花崗巖亞類。據(jù)微量元素構(gòu)造辨別圖解,研究區(qū)堿長花崗巖均落入同碰撞花崗巖區(qū)和火山弧花崗巖區(qū),屬于火山弧后環(huán)境。
[Abstract]:The study area is located in the northwest of Sunita Zuo Banner area, Inner Mongolia. The tectonic location is the east segment of Central Asian orogenic belt-Xingmeng orogenic belt.The tectonic units in this area are divided into the northern orogenic belt of Xingmeng orogenic belt, the Erlian-Hegenshan fault zone in the south and the active continental margin of Siberia in the north.The Paleozoic belongs to the Paleo-Asian oceanic tectonic domain and enters the Mesozoic and belongs to the West Coast Pacific tectonic domain.The exposed strata in the study area include the clastic rocks of the first member of the Baoligaomiao formation of the Carboniferous, the volcanic rocks of the Cretaceous and the Damokuahe formation of the Cretaceous system, the Paleogene Yerdingmanha formation and the Quaternary system.The margin of alkali-feldspar granite body is covered by the eruption unconformity of Baiyingao formation volcanic rocks.The granitic rock assemblages in the study area are mainly composed of alkali feldspar granite, monzomorphic granite and granodiorite.In this paper, the alkali-feldspar granite is studied.The alkali feldspar granite basement was exposed to the north of Chagan Aoba-Aronqi fault and was intruded by porphyry granodiorite in the area of Tudaulege.The alkali-feldspar granitic body developed the porphyry granodiorite vein and the porphyry biotite monzogranite vein.The zircon U-Pb isotopic dating of alkali feldspar granites obtained 206Pb/U238 weighted mean age of 312.2Ma 鹵7.4 Ma-MSWDN 6.67, which belongs to the late Carboniferous.The geochemical analysis shows that the alkali feldspar granite is high in silicon and rich in alkali, indicating the geochemical characteristics of calc-alkaline magma.The fractionation of heavy and heavy rare earth elements in alkali feldspar granite is not obvious, and it has obvious negative EU anomaly, which is typical "seagull-type rare earth partition curve".On the primitive mantle-normalized trace element cobweb map, the alkali feldspar granite is characterized by obvious depletion of the incompatible element BaHNbNbCE-Sr-Ti and enrichment of the compatible element RbCU Th, which indicates the characteristics of the crustal magma source region.The alkali feldspar granites have a high 10000Ga/Al ratio and a high Zn ~ (2 +) Zr ~ (2 +) Y ~ (+) ce content, and are distributed in the A-type granite area on the classification diagram of the granites.They are high in Ga and Y, low in NB and belong to A 2-granite subclass.According to the trace element structure distinguishing diagram, the alkali feldspar granites in the study area all fall into the syncollision granite area and the volcanic arc granite area, which belong to the behind volcanic arc environment.
【學(xué)位授予單位】：石家莊經(jīng)濟(jì)學(xué)院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121

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本文編號：1722948