本文選題：早古生代花崗巖 + 中生代花崗巖��； 參考：《南京大學(xué)》2015年博士論文

【摘要】：作為大陸地殼重要的組成部分,花崗巖的巖石成因與大陸地殼的演化存在密切的聯(lián)系。侵位于滇東南老君山地區(qū)的早古生代花崗巖和晚中生代花崗巖是該區(qū)最重要的侵入體,對于其成因,特別是源區(qū)的性質(zhì)和形成的地球動力學(xué)背景尚需要深入的研究。華南早古生代造山作用一直以來都是學(xué)術(shù)研究的熱點,其中一個關(guān)鍵問題是造山運動所引起的花崗質(zhì)巖漿作用過程中是否有地幔物質(zhì)的參與。針對這一科學(xué)問題,本文對華南板塊西部滇東南老君山地區(qū)三期典型的早古生代花崗巖(團田單元,南撈單元,老城坡單元)進行了詳細的地質(zhì)年代學(xué)和地球化學(xué)研究。LA-ICP-MS鋯石U-Pb年代學(xué)顯示這三期花崗巖的結(jié)晶年齡分別為～436Ma,～430Ma,～427Ma。其巖漿鋯石的￡Hf(t)值為-14～+3,指示這三期花崗巖的源區(qū)具有不均一性的特征。三期巖體均包含繼承鋯石核,其U-Pb年代和Hf模式年齡為元古代。大量的主微量元素協(xié)變組合顯示老君山早古生代花崗巖具有明顯的線性混合趨勢。其中團田和南撈單元巖體具有強過鋁質(zhì)的地球化學(xué)特征(A/CNK1.1),而老城坡單元巖體具有弱過鋁質(zhì)特征(A/CNK=1.0～1.1)。相對于老城坡單元巖體,團田和南撈單元巖體表現(xiàn)為高K_2O、Rb/Sr、Rb/Ba和εNd(t)值,低 TFe_2O_3、Al_2O_3、MnO、MgO、CaO、TiO_2、Na_2O、Mg#和Nb/Ta值的特征。上述事實表明團田和南撈單元花崗巖形成于部分熔融的元古代變質(zhì)沉積巖,其中基本上沒有幔源物質(zhì)的參與;然而,老城坡花崗巖很可能來源于殼源長英質(zhì)熔體和幔源基性巖漿的混合作用。值得注意的是幔源組分相對于殼源組分具有更低的Nd同位素組成,而這與華南最近發(fā)現(xiàn)的幔源玄武巖具有一致的同位素特征。武夷-云開造山垮塌造成了早古生代華夏板塊下地殼的部分熔融。其廣泛的早古生代花崗質(zhì)巖漿作用,以及伴隨出現(xiàn)的幔源巖漿,表明了這個時期華南板塊西部處于后碰撞伸展的構(gòu)造環(huán)境。軟流圈的上涌和玄武質(zhì)巖漿的底侵很可能引起了華南板塊西部大規(guī)模的長英質(zhì)巖漿作用,幔源熔體在這個過程中提供了能量和物質(zhì)。我們本次研究還對老君山地區(qū)與成礦有關(guān)的三類晚中生代花崗巖,包括中粗�；◢弾r、中細�；◢弾r和花崗斑巖,進行詳細的地質(zhì)年代學(xué)、主微量元素、礦物化學(xué)和Nd-Hf同位素研究。這三類花崗巖的鋯石U-Pb定年結(jié)果分別為90.1±0.7 Ma,89.7±0.8 Ma,86.0±0.5 Ma,顯示其在同一時期發(fā)生侵位。所有樣品均顯示強過鋁質(zhì)、富堿的特征,元素特征表現(xiàn)為高P、Li、Rb、Cs、Ta、Sn、W 和 U,低 Ti、Mg、Co、Ni、Sr、Ba、Zr、Hf、Th 及稀土元素。巖漿在運移過程中發(fā)生了明顯的分異演化作用,其中斜長石和鉀長石的結(jié)晶分異作用主要控制巖漿中Rb、Sr、Ba和Eu的濃度;而磷灰石、獨居石等副礦物結(jié)晶分異作用則影響著稀土元素含量。地球化學(xué)特征顯示老君山地區(qū)晚中生代花崗巖主要為高分異S型花崗巖。全巖εNd(t)值為-12.2～-10.8,鋯石εHf(t)值為-15.5～-2.5,其Nd和Hf同位素兩階段模式年齡均為中-古元古代。研究表明,這些S型花崗巖均起源于中-古元古代陸殼中類似變質(zhì)泥巖組分的部分熔融。老君山地區(qū)這三類晚中生代花崗巖的Sn含量遠高于大陸上地殼和下地殼的平均值,屬于含錫花崗巖。本次研究還對老君山地區(qū)-都龍超大型錫礦中的主要成礦礦物錫石進行了詳細的錫石LA-MC-ICP-MS U-Pb定年,獲得206Pb/207Pb-238U/207Pb等時線年齡為86.6～90.6Ma,表明都龍礦區(qū)錫成礦作用主要發(fā)生在晚白堊紀(jì),這與本次研究所測得老君山地區(qū)晚中生代含錫花崗巖的成巖年齡相一致。緊密的時間以及空間關(guān)系顯示老君山地區(qū)晚中生代巖漿熱液活動是都龍礦區(qū)錫成礦作用的關(guān)鍵。對含錫花崗巖中主要造巖礦物的電子探針研究進一步支持了富含揮發(fā)組分(F,C1)的老君山含錫巖漿主要起源于成熟度較高的地殼源區(qū)。其中黑云母電子探針成分顯示含錫花崗巖的氧逸度低于Ni-NiO(NNO)體系,表明其巖漿結(jié)晶過程處于相對還原的環(huán)境。在低氧逸度還原條件下,Sn在巖漿中主要呈二價形式存在,具有較大的離子半徑,因此Sn2+不易進入到成巖礦物的晶格中,而傾向于在結(jié)晶分異晚期的殘余熔體和流體中富集。因此,老君山地區(qū)晚中生代巖漿演化過程中高程度的分異結(jié)晶作用有利于Sn在花崗質(zhì)巖漿中發(fā)生初次富集,而晚期巖漿還原性的條件(fO_2NNO)使Sn在運移過程中更傾向于進入到熱液流體中從而導(dǎo)致錫的再次富集,最終在有利的構(gòu)造部位發(fā)生沉淀形成錫礦化。都龍超大型錫多金屬礦床位于老君山地區(qū)西南部,是中國第三大錫石硫化物礦床,其錫的儲量約30萬噸。而與其相鄰的個舊地區(qū)還存在中國第一大錫礦床-個舊超大型錫多金屬礦床。作為滇東南地區(qū)兩個世界級的錫多金屬礦區(qū),老君山和個舊具有一致的晚白X 世成巖成礦時代,因而綜合對比這兩個地區(qū)同時期的巖漿巖有助于更好地理解整個區(qū)域在這個時期的巖漿演化歷史與成礦構(gòu)造背景。相比于同時期的個舊礦區(qū)花崗巖,老君山地區(qū)花崗巖具有高的 Rb、Rb/Sr、初始 87Sr/86Sr 和鋯石εHf(t)值,低的 TFe_2O_3、Al_2O_3、MgO、TiO_2、P_2O_5 和稀土元素含量。地球化學(xué)結(jié)果顯示強過鋁質(zhì)的老君山花崗巖很可能代表長英質(zhì)端元組分,其起源于純殼源的中-古元古代變質(zhì)沉積巖中泥質(zhì)組分的部分熔融,而個舊花崗巖則可能來源于殼源巖漿(如老君山花崗質(zhì)巖漿)和幔源基性巖漿(個舊輝長巖-細粒鎂鐵質(zhì)包體MME)的混合作用。老君山和個舊地區(qū)巖漿作用很可能反映華南板塊西部在晚白堊世處于伸展的板內(nèi)構(gòu)造環(huán)境。上涌的軟流圈地幔及底侵的玄武質(zhì)巖漿引起了上覆陸殼中變質(zhì)沉積巖的部分熔融,從而形成S型花崗質(zhì)巖漿(如老君山花崗巖),而幔源基性巖漿注入淺部地殼,同時與殼源長英質(zhì)巖漿發(fā)生混合作用形成個舊(花崗巖-MME-輝長巖)雜巖體。這種巖漿作用的差異也同時合理地反映在這兩個地區(qū)細微成礦差異上。通常相對高含量的Cu賦存于地幔,而相對高含量的Sn賦存于地殼。起源于純殼源巖漿的老君山地區(qū)主要形成以Sn-Zn礦化為主的都龍錫多金屬礦床,而經(jīng)歷了廣泛的殼幔相互反應(yīng)的個舊地區(qū)則形成了以Sn-Cu礦化為主的個舊錫多金屬礦床。
[Abstract]:As an important part of the continental crust, the petrogenesis of the granite is closely related to the evolution of the continental crust. The early Palaeozoic granites and late Mesozoic granites, which are located in the Laojun Mountain area in southeastern Yunnan, are the most important intrusive bodies in this area, and their genesis, especially the nature of the source area and the geodynamic background of the formation, is still yet to be found. The early Paleozoic orogeny in Southern China has always been a hot spot of academic research. One of the key problems is whether the mantle material is involved in the granitic magmatism caused by the orogenic movement. In view of this scientific problem, this paper is a typical early stage of the three stage of the Laojun Mountain area in the Western Southern China, the western part of the Southern China plate. .LA-ICP-MS zircon U-Pb chronology of geological chronology and geochemistry of the Palaeozoic granites (group field unit, South fishing unit, and old city slope unit) shows that the crystallization ages of these three phases of granites are 436Ma, 430Ma and 427Ma. Hf (T) of the magma zircon is -14 to +3, indicating the source area of the three periods of granites. The characteristics of heterogeneity. The three phase of the rock mass contains the inherited zircon core, and its U-Pb age and Hf model age are Proterozoic. A large number of major and microelement covariant combinations show that the early Palaeozoic granites in Laojun Mountain have obvious linear mixing trend. The rock mass of the urban slope unit has a weak peraluminous character (A/CNK=1.0 ~ 1.1). Compared with the old city slope unit rock mass, the mass of the Tuan Tian and the Nan salvo unit shows a high K_2O, Rb/Sr, Rb/Ba and epsilon Nd (T) values, which are low TFe_2O_3, Al_2O_3, MnO, MgO, and CaO. The metamorphic sedimentary rocks of the Proterozoic are basically not involved in the mantle derived materials; however, the old city slope granites are likely to be derived from the mixture of crust source feldspar and mantle derived basic magma. It is worth noting that the mantle source composition has a lower Nd isotope composition relative to the source component of the crust, and this is with the mantle derived basalts recently discovered in Southern China. The rock has consistent isotopic characteristics. Wuyi - Yunkai orogeny resulted in the partial melting of the lower crust of the early Paleozoic Cathaysian plate. Its extensive early Palaeozoic granitic magmatism and the accompanying mantle derived magma showed the tectonic setting of the western Southern China plate in the post collision extension. The upwelling and basaltic of the asthenosphere. The undergression of the magma may lead to a large amount of felsic magmatism in the western part of the Southern China plate. The mantle derived melts provided energy and substance in this process. In this study we also studied three types of Late Mesozoic granites related to mineralization in the Laojun Mountain area, including mesogranitic granite, medium fine granites and granite porphyry. Fine geological chronology, main trace elements, mineral chemistry and Nd-Hf isotopes. The zircon U-Pb dating results of these three types of granites are 90.1 + 0.7 Ma, 89.7 + 0.8 Ma and 86 + 0.5 Ma, showing emplacement at the same time. All samples show strong peraluminous, alkali rich characteristics, and the elements are characterized by high P, Li, Rb, Cs, Ta, Sn, W and U, low Ti, Mg, Co, Ni, Sr, Ba, Zr, Hf, Th and rare earth elements. The magma has obvious differentiation and evolution during the migration process, in which the crystallization differentiation of plagioclase and potassium feldspar mainly controls Rb, Sr, and concentration in magma, while the crystallization of apatite and monazite influences the content of rare earth elements. Geochemistry The characteristics show that the late Mesozoic granites in the Laojun Mountain area are mainly high fractionated S type granites. The total rock epsilon Nd (T) value is -12.2 to -10.8, the zircon epsilon Hf (T) value is -15.5 to -2.5, and the two stage model age of Nd and Hf isotopes are both middle and Paleoproterozoic. The Sn content of the three types of Late Mesozoic granites in the Laojun Mountain area is far higher than the average value of the continental upper crust and lower crust, and it belongs to the tin bearing granite. This study also made a detailed stannite LA-MC-ICP-MS U-Pb dating for the major metallogenic mineral deposits in the Laojun Mountain Region - Du long super large tin deposit, and obtained 206Pb/207Pb-23 The 8U/207Pb isochronous line age is 86.6 ~ 90.6Ma, indicating that the tin mineralization in the Ditong mining area mainly occurred in the late Cretaceous period, which is in accordance with the age of diagenesis of the late Mesozoic tin bearing granite in the Laojun Mountain area. The close time and spatial relationship showed that the late Mesozoic magmatic hydrothermal activity in the Laojun Mountain area was the tin in the Dulong mining area The electron probe study of the main rock forming minerals in the tin bearing granite further supports the origin of the Laojun Mountain containing F (C1) rich in the high maturity of the crust source. The biotite electron probe composition shows that the oxygen fugacity of the tin bearing granite is lower than the Ni-NiO (NNO) system, indicating that its magma is magma The crystallization process is in a relative reduction environment. Under the condition of low oxygen fugacity, Sn exists mainly in the two valence form of the magma and has a larger ionic radius. Therefore, Sn2+ is not easy to enter the lattice of the diagenetic mineral, but tends to be enriched in the residual melt and flow body in the late crystallization differentiation. Therefore, the late Mesozoic magma in the Laojun Mountain area In the process of evolution, the high degree of differentiation crystallization is beneficial to the initial enrichment of Sn in the granitic magma, and the condition of late magma reducibility (fO_2NNO) makes Sn more inclined to enter the hydrothermal fluid in the process of migration, which leads to the re enrichment of tin, and eventually precipitates in the favorable tectonic site to form tin mineralization. The tin polymetallic deposit is located in the southwest of Laojun Mountain area. It is the third largest cassiterite sulfide deposit in China. Its tin reserves are about 300 thousand tons. There are also the first largest tin deposits in the adjacent areas, the old super large tin polymetallic deposit. As two world-class tin polymetallic ore deposits in southeastern Yunnan, the Laojun Mountain and the old are of the old. Unanimous late white X
In the age of diagenesis and mineralization, the comprehensive comparison of the two regions of the same period of magmatism helps to better understand the whole region's magmatic evolution history and metallogenic tectonic setting in this period. Compared with the granite in the same old mining area, the granite in the Laojun Mountain area has high Rb, Rb/Sr, initial 87Sr/86Sr and zircon epsilon Hf (T) values. TFe_2O_3, Al_2O_3, MgO, TiO_2, P_2O_5 and rare earth elements. The geochemical results show that the strong peraluminous Laojun Mountain granite is likely to represent the felsic end tuple, which originated from the partial melting of the argillaceous components in the Mesoproterozoic metamorphic sedimentary rocks of the pure crustal source, and the old granite may be derived from the crust source magma (such as the old gentleman. The mixture of mantle derived granitic magma and mantle derived basic magma (the old gabbro - fine mafic inclusion MME). The magmatism in Laojun Mountain and the old area may reflect the extensional tectonic environment of the western Southern China plate in the late Cretaceous. The upwelling of the asthenosphere mantle and the basaltic magma from the bottom of the basaltic magma caused the metamorphism in the overlying continental crust. The partial melting of sedimentary rocks formed S granitic magma (such as the Laojun Mountain granite), and the mantle derived basic magma injected into the shallow crust and mixed with the crust source felsic magma to form an old (granite -MME- gabbro) complex. The difference of this magmatism is also reasonably reflected in the subtle mineralization in the two regions. Generally, the relatively high content of Cu occurs in the mantle, while the relatively high content of Sn exists in the crust. The Laojun Mountain area, which originated from the pure crust source magma, mainly formed the Dulong tin polymetallic deposit, mainly with Sn-Zn mineralization, and the old area, which has experienced a wide range of crust and mantle interaction, formed an old tin polymetallic deposit dominated by Sn-Cu mineralization. Deposit.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：P588.11;P611

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