西秦嶺中川花崗巖體年代學(xué)、地球化學(xué)、巖漿混合成因
發(fā)布時間：2018-12-13 10:32
【摘要】：西秦嶺造山帶位于中國腹心地帶秦嶺造山帶的西段,是中國中央造山帶的重要組成部分。中川花崗巖體位于西秦嶺構(gòu)造帶東部禮縣-羅壩-鎖龍口斷裂和禮縣-洮坪斷裂兩大斷裂之間,主要侵位于泥盆系舒家壩群和西漢水群中。其巖石類型主要為中粗粒似斑狀黑云二長花崗巖、中粒含斑黑云二長花崗巖以及中細粒黑云二長花崗巖,這些巖石由外向內(nèi)依次呈同心圓狀分布。巖體中巖漿暗色包體發(fā)育,同時也發(fā)育后期侵入的細�；◢弾r脈。LA-ICPMS鋯石U-Pb定年顯示,似斑狀黑云二長花崗巖的年齡為221±1Ma(MSDW=0.26),細粒黑云二長花崗巖為217±1Ma(MSDW=0.107);含斑晶巖漿暗色包體為220±1Ma(MSDW=0.107),細粒巖漿暗色包體為216±1Ma(MSDW=0.26);細�；◢弾r脈為207±1Ma(MSDW=0.29)。這表明該巖體從邊部到中心年齡有逐漸變新的趨勢,暗色包體和寄主巖石的形成年齡基本一致,巖脈的形成時間最晚。中川巖體中不同寄主巖石類型在礦物組成上基本一致,為堿性長石+斜長石+石英+黑云母±角閃石組合,暗色礦物以黑云母為主,可見少量角閃石,不含石榴子石、堇青石等富鋁礦物,巖體中心晚期的細粒黑云二長花崗巖不含角閃石,并有極少量的白云母出現(xiàn)。巖漿暗色包體主要分布于巖體邊部,礦物組成為黑云母、角閃石、石英、斜長石、堿性長石,巖石類型為細粒石英閃長巖,部分包體內(nèi)部包裹鉀長石巨晶。中川巖體寄主巖石的A/CNK=0.99~1.15,具高硅、鋁和富堿的特點,屬高鉀鈣堿系列,準鋁質(zhì)-弱過鋁質(zhì)I型花崗巖,同時細粒黑云二長花崗巖A/CNK大于1.1,鐵鎂含量較低,出現(xiàn)少量白云母,為高分異I型花崗巖。巖漿暗色包體具低硅、富鋁和富堿的特點,屬鉀玄巖-高鉀鈣堿系列,準鋁質(zhì)巖。寄主巖石和巖漿暗色包體均表現(xiàn)出輕稀土相對富集的右傾的特征,輕、重稀土元素分餾明顯,具弱的負銪異常;均富集LREE、Rb、Ba、K等大離子親石元素,虧損HREE、Zr、Hf、Ta、Nb、P、Ti等高場強元素。同位素組成上,寄主巖石與暗色包體的εNd(t)分別變化于-7.31~-8.73和-5.32~-5.69之間,TDM2分別變化于1.59~1.71Ga和1.43~1.46Ga之間,εHf(t)值分別為-7.02~-0.31和-3.0~0,TDMC為1.27~1.70Ga和1.2~1.5Ga,暗色包體發(fā)育淬冷邊和針狀磷灰石,反映寄主花崗巖和巖漿暗色包體分別來源于不同源區(qū),寄主巖石主要是古老地殼物質(zhì)部分熔融的結(jié)果,暗色包體巖漿可能是來自巖石圈地幔,但與寄主花崗質(zhì)巖漿已發(fā)生了一定的混合。該巖體外圍金礦床的成礦年齡(171~210Ma)稍晚于巖體形成年齡,并且?guī)r體、礦區(qū)巖脈以及金礦床年齡相近,金礦與巖體時空上聯(lián)系密切,結(jié)合前人成礦物質(zhì)來源的研究,認為成礦物質(zhì)與成巖物質(zhì)具有相似性。這表明該巖體與其周圍的金礦可能具有同源性和繼承性演化的特點。
[Abstract]:The West Qinling orogenic belt is an important part of the central orogenic belt of China, which is located in the western part of the Qinling orogenic belt in the ventral heart of China. The Zhongchuan granite body is located between the Lixian-Luoba-Suolongkou fault and the Lixian-Taoping fault in the eastern part of the western Qinling structural belt, and mainly transgressions in the Devonian Shujiaba group and the western Han water group. The rock types are mainly medium-coarse porphyry bifeldite, mesomorphic porphyry bifeldite and medium-fine-grained black cloud monzogranite. These rocks are distributed in concentric circles from outside to inside. LA-ICPMS zircon U-Pb dating shows that the age of porphyry bifeldspar granite is 221 鹵1Ma (MSDW=0.26). The fine grained bifeldite is 217 鹵1Ma (MSDW=0.107); The dark color inclusion of porphyry magma is 220 鹵1Ma (MSDW=0.107), the dark color inclusion of fine-grained magma is 216 鹵1Ma (MSDW=0.26), and the vein of granitic granite is 207 鹵1Ma (MSDW=0.29). This indicates that the age from the edge to the center of the rock body is gradually changing, the age of formation of the dark inclusion is basically the same as that of the host rock, and the formation time of the vein is the latest. The mineral composition of different host rocks in Zhongchuan rock mass is basically the same, which is composed of alkaline feldspar plagioclase quartz biotite 鹵hornblende assemblage, dark mineral is mainly biotite, a small amount of hornblende and no garnet is found. Cordierite and other aluminum-rich minerals, the late fine-grained biotite monzonitic granites in the center of the rock body do not contain amphibole, and a very small amount of Muscovite appears. The magmatic dark inclusion is mainly distributed at the edge of the rock body, and the mineral composition is biotite, hornblende, quartz, plagioclase, alkaline feldspar, the rock type is fine quartz diorite, and some inclusions contain potassium feldspar megacrystals. The A / CNK ~ (0.99) ~ (1.15) of the host rocks of the Zhongchuan rock body is characterized by high silicon, aluminum and alkali, belonging to the high potassium calcium alkali series, quasi-aluminum-weakly peraluminous I-type granite, and the fine grained black cloud monzomorphic granite (A/CNK > 1.1). The content of Fe and mg is low and a small amount of Muscovite, which is a high differentiation I type granite. The magmatic dark inclusion is characterized by low silicon, rich in aluminum and alkali. It belongs to the series of potash-high potassium calcium alkali, quasi-aluminous rock. The dark inclusions of host rocks and magma show the characteristics of relative enrichment of LREE to the right, light and heavy REE fractionation is obvious, with weak negative europium anomaly. All of them are rich in large ion lithophile elements such as LREE,Rb,Ba,K and depleted high field strength elements such as HREE,Zr,Hf,Ta,Nb,P,Ti. In isotopic composition, 蔚 Nd (t) of host rocks and dark inclusions varied from -7.31 to 8.73 and -5.32 to 5.69, and TDM2 to 1.59~1.71Ga and 1.43~1.46Ga, respectively. The 蔚 Hf (t) values were -7.02 ~ (-0.31) and -3.0 ~ 0 ~ (-1) 1.27~1.70Ga, respectively. The dark inclusion developed quenching edge and acicular apatite, which indicated that the host granite and magmatic dark inclusion originated from different source regions, respectively. The host rocks are mainly the result of partial melting of ancient crustal materials. The dark inclusion magma may come from the lithospheric mantle, but has been mixed with the host granitic magma to some extent. The metallogenic age (171~210Ma) of the peripheral gold deposit is slightly later than that of the rock mass, and the age of the ore body, the vein and the gold deposit is similar, and the gold deposit is closely related to the rock mass in time and space. It is considered that the ore-forming material is similar to the diagenetic material. This indicates that the rock may have the characteristics of homology and succession evolution with the gold deposits around it.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121;P597.3
本文編號：2376395
[Abstract]:The West Qinling orogenic belt is an important part of the central orogenic belt of China, which is located in the western part of the Qinling orogenic belt in the ventral heart of China. The Zhongchuan granite body is located between the Lixian-Luoba-Suolongkou fault and the Lixian-Taoping fault in the eastern part of the western Qinling structural belt, and mainly transgressions in the Devonian Shujiaba group and the western Han water group. The rock types are mainly medium-coarse porphyry bifeldite, mesomorphic porphyry bifeldite and medium-fine-grained black cloud monzogranite. These rocks are distributed in concentric circles from outside to inside. LA-ICPMS zircon U-Pb dating shows that the age of porphyry bifeldspar granite is 221 鹵1Ma (MSDW=0.26). The fine grained bifeldite is 217 鹵1Ma (MSDW=0.107); The dark color inclusion of porphyry magma is 220 鹵1Ma (MSDW=0.107), the dark color inclusion of fine-grained magma is 216 鹵1Ma (MSDW=0.26), and the vein of granitic granite is 207 鹵1Ma (MSDW=0.29). This indicates that the age from the edge to the center of the rock body is gradually changing, the age of formation of the dark inclusion is basically the same as that of the host rock, and the formation time of the vein is the latest. The mineral composition of different host rocks in Zhongchuan rock mass is basically the same, which is composed of alkaline feldspar plagioclase quartz biotite 鹵hornblende assemblage, dark mineral is mainly biotite, a small amount of hornblende and no garnet is found. Cordierite and other aluminum-rich minerals, the late fine-grained biotite monzonitic granites in the center of the rock body do not contain amphibole, and a very small amount of Muscovite appears. The magmatic dark inclusion is mainly distributed at the edge of the rock body, and the mineral composition is biotite, hornblende, quartz, plagioclase, alkaline feldspar, the rock type is fine quartz diorite, and some inclusions contain potassium feldspar megacrystals. The A / CNK ~ (0.99) ~ (1.15) of the host rocks of the Zhongchuan rock body is characterized by high silicon, aluminum and alkali, belonging to the high potassium calcium alkali series, quasi-aluminum-weakly peraluminous I-type granite, and the fine grained black cloud monzomorphic granite (A/CNK > 1.1). The content of Fe and mg is low and a small amount of Muscovite, which is a high differentiation I type granite. The magmatic dark inclusion is characterized by low silicon, rich in aluminum and alkali. It belongs to the series of potash-high potassium calcium alkali, quasi-aluminous rock. The dark inclusions of host rocks and magma show the characteristics of relative enrichment of LREE to the right, light and heavy REE fractionation is obvious, with weak negative europium anomaly. All of them are rich in large ion lithophile elements such as LREE,Rb,Ba,K and depleted high field strength elements such as HREE,Zr,Hf,Ta,Nb,P,Ti. In isotopic composition, 蔚 Nd (t) of host rocks and dark inclusions varied from -7.31 to 8.73 and -5.32 to 5.69, and TDM2 to 1.59~1.71Ga and 1.43~1.46Ga, respectively. The 蔚 Hf (t) values were -7.02 ~ (-0.31) and -3.0 ~ 0 ~ (-1) 1.27~1.70Ga, respectively. The dark inclusion developed quenching edge and acicular apatite, which indicated that the host granite and magmatic dark inclusion originated from different source regions, respectively. The host rocks are mainly the result of partial melting of ancient crustal materials. The dark inclusion magma may come from the lithospheric mantle, but has been mixed with the host granitic magma to some extent. The metallogenic age (171~210Ma) of the peripheral gold deposit is slightly later than that of the rock mass, and the age of the ore body, the vein and the gold deposit is similar, and the gold deposit is closely related to the rock mass in time and space. It is considered that the ore-forming material is similar to the diagenetic material. This indicates that the rock may have the characteristics of homology and succession evolution with the gold deposits around it.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121;P597.3
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