海南省抱倫金礦變質(zhì)基性巖成因及與金成礦作用關(guān)系
發(fā)布時間：2018-09-09 18:17
【摘要】：抱倫金礦位于海南省西南部,東西向尖峰-吊羅斷裂和九所-陵水斷裂之間,北東向白沙斷裂的西側(cè),是目前海南省規(guī)模最大的高品位金礦床。抱倫金礦是典型的石英脈型金礦,礦體受礦區(qū)豪崗嶺背斜和發(fā)育在背斜核部的NNW向斷裂破碎帶控制。在對海南省抱倫金礦進行研究的過程中,我們在礦井中發(fā)現(xiàn)大量的變質(zhì)基性巖和金礦脈在空間上緊密伴生。本文結(jié)合前人對礦床的研究,在野外地質(zhì)調(diào)查的基礎(chǔ)上,開展了巖相學和成因礦物學研究、全巖地球化學和Sm-Nd同位素組成分析、以及SHRIMP鋯石U-Pb定年,并結(jié)合全巖金豐度分析,探討了變質(zhì)基性巖的巖漿源區(qū)特征和產(chǎn)出構(gòu)造環(huán)境,以及這些基性巖與抱倫金礦的成礦作用關(guān)系,取得的主要成果和認識如下:(1)根據(jù)野外產(chǎn)狀和地球化學特征,變質(zhì)基性巖可以分為兩組。在野外產(chǎn)狀方面,第一組呈細脈狀產(chǎn)出,與地層、石英脈混雜,局部可見石英和地層透鏡體;第二組變質(zhì)基性巖脈較寬、延伸大,脈體較干凈。在地球化學特征上,第一組樣品的REEs含量較高,為球粒隕石的20~80倍,且表現(xiàn)出強烈的LREE富集和Eu的負異常(但BL-065和13BL-87有輕微正異常),相對于N-MORB富集Th、Ta、Nb和Ce,在蛛網(wǎng)圖上形成中間“隆起”,εNd(230Ma)值大多處于-6.62~-4.45之間;第二組樣品的REEs含量相對較低,為球粒隕石的14~40倍,大多表現(xiàn)出LREE虧損的稀土配分模式(13BL-44除外)和Eu的正異常(但13BL-71有輕微負異常),且相對N-MORB富集Sr、K、Rb和Ba等LIL元素和Th,LIL/HFS比值高,εNd(230Ma)值分布于0.33~5.65之間。兩組變質(zhì)基性巖的主要硅酸鹽礦物都為斜長石和角閃石,主要金屬礦物為磁鐵礦、黃鐵礦和黃銅礦。第一組變質(zhì)基性巖中有石英出現(xiàn),局部亦出現(xiàn)碳酸鹽,金屬礦物還有少量閃鋅礦;第二組變質(zhì)基性巖中局部可見殘留輝石和蝕變礦物綠泥石、綠簾石、黝簾石、絹云母、黑云母和碳酸鹽等。(2)地球化學特征表明,第一組樣品的巖漿源區(qū)盡管也是虧損地幔源區(qū),但主要受到的是富集地幔源區(qū)的混染,同時有少量地殼成分的加入,幾乎未受到過俯沖帶含水流體的影響。兩組樣品的巖漿源區(qū)均較淺,源區(qū)沒有石榴石相的殘余;而第二組樣品的巖漿源區(qū)可能是受到過俯沖帶含水流體影響的虧損地幔源區(qū),具有島弧巖漿的性質(zhì),幾乎未受到過富集巖石圈地幔的影響,可能受到過少量地殼的混染。第一組樣品形成于以分離結(jié)晶為主的巖漿演化過程,分離結(jié)晶的礦物組合是單斜輝石+斜長石±橄欖石;第二組樣品形成于以部分熔融為主的巖漿演化過程。(3)通過挑選變質(zhì)基性巖中的鋯石進行SHRIMP U-Pb定年,獲得第二組變質(zhì)基性巖的成巖年齡為231.6±2.6Ma,此年齡和尖峰巖體的成巖年齡208~249Ma、抱倫金礦的成礦年齡224.6±7.2Ma相近。而且,在地理位置上,本次研究的變質(zhì)基性巖和尖峰巖體也相鄰。結(jié)合變質(zhì)基性巖的地球化學特征和尖峰巖體構(gòu)造環(huán)境的研究成果推斷,變質(zhì)基性巖產(chǎn)出于后碰撞階段伸展的構(gòu)造環(huán)境。根據(jù)變質(zhì)基性巖的地球化學特征和年代學特征,綜合前人對華南構(gòu)造背景的研究,古特提斯洋東段在海南島閉合時,洋殼自北向南俯沖進入南部塊體之下,并于208~249Ma左右處于后碰撞階段。(4)變質(zhì)基性巖的金豐度分析結(jié)果表明,第二組變質(zhì)基性巖中部分樣品的金豐度遠遠高于地殼克拉克值,且數(shù)據(jù)離散度大,顯示出Au自變質(zhì)基性巖中被活化、遷移的跡象。地球化學特征表明,第二組變質(zhì)基性巖的巖漿是Au運移的合適載體。地質(zhì)年代學結(jié)果顯示,變質(zhì)基性巖的成巖年齡和抱倫金礦的成礦年齡在誤差范圍內(nèi)一致。因此,第二組變質(zhì)基性巖可能在成礦作用中提供了Au。(5)綜合以上分析,抱倫金礦變質(zhì)基性巖產(chǎn)出和金成礦的模型應為:后碰撞構(gòu)造環(huán)境下,兩種變質(zhì)基性巖先后依次產(chǎn)出。其中,發(fā)育較晚的一組基性巖將成礦物質(zhì)Au從深部攜帶到淺部后,其基性巖漿熱液攜帶著Au等成礦元素和尖峰巖體的酸性巖漿熱液混合,并沿著裂隙運移上升。志留系陀烈組的含碳千枚巖和從地表滲下的天水使成礦流體的化學性質(zhì)發(fā)生改變,Au富集成礦。(6)本文的研究表明,抱倫金礦成礦的時間對應著造山運動的后碰撞階段以及從擠壓向伸展轉(zhuǎn)換的應力機制。相鄰的尖峰-吊羅斷裂應為切穿大陸巖石圈的深大斷裂。結(jié)合前人研究成果,抱倫金礦應為造山型金礦。
[Abstract]:Baolun gold deposit is located in the southwest of Hainan Province, between the East-West spike-suspension fault and Jiusuo-Lingshui fault, and on the west side of the north-east Baisha fault. It is the largest high-grade gold deposit in Hainan Province at present. Control. During the study of Baolun gold deposit in Hainan Province, we found a large number of metamorphic basic rocks and gold veins closely associated in space. Based on the previous study of the deposit and on the basis of field geological survey, this paper carried out lithofacies and genetic mineralogy, whole rock geochemistry and Sm-Nd isotope composition. Based on the analysis and SHRIMP zircon U-Pb dating, and combined with the analysis of the whole rock gold abundance, the magmatic source area characteristics and occurrence tectonic setting of metamorphic basic rocks, and the relationship between these basic rocks and the mineralization of the Baolun gold deposit are discussed. The main achievements and understandings are as follows: (1) According to the field occurrence and geochemical characteristics, metamorphic basic rocks can be divided into metamorphic basic rocks. In the field occurrence, the first group occurs as fine veins, intermingled with strata, quartz veins, locally visible quartz and stratigraphic lenses; the second group metamorphic basic dikes are wider, larger, and more clean. In geochemical characteristics, the REEs content of the first group is 20-80 times higher than that of chondrites, and shows strong LREE enrichment. Negative anomalies with Eu (but slightly positive anomalies with BL-065 and 13BL-87), compared with N-MORB enrichment of Th, Ta, Nb and Ce, formed an intermediate "uplift" on the cobweb, and the values of epsilon Nd (230Ma) were mostly between - 6.62 and - 4.45; the second group of samples had relatively low REEs content, 14-40 times that of chondrites, mostly showing LREE depletion patterns (13BL-44). Except for positive anomalies (but slightly negative anomalies in 13BL-71) and Eu, the LIL elements such as Sr, K, Rb and Ba are enriched and the ratio of LIL to HFS is high relative to N-MORB, and the value of epsilon Nd (230 Ma) is distributed between 0.33 and 5.65. The main silicate minerals of the two groups of metamorphic basic rocks are plagioclase and amphibole, and the main metal minerals are magnetite, pyrite and chalcopyrite. Quartz appears in the metamorphic basic rocks, carbonate occurs locally, metallic minerals and a small amount of sphalerite. Residual pyroxene and altered minerals such as chlorite, epidote, epidote, sericite, biotite and carbonate can be found locally in the metamorphic basic rocks of the second group. (2) Geochemical characteristics show that although the magma source area of the first group is also deficient. The source area of the two groups of samples is shallow, and there is no residual garnet facies in the source area. The source area of the second group of samples may be affected by the water-bearing fluid in the subduction zone. The first group of samples were formed during the magmatic evolution process dominated by separation crystallization, and the mineral assemblage of separation crystallization was clinopyroxene + plagioclase + olivine. (3) By selecting zircons from metamorphic basic rocks for SHRIMP U-Pb dating, the diagenetic age of the second group of metamorphic basic rocks is 231.6+2.6 Ma, which is similar to the diagenetic age of the Jianfeng pluton from 208 to 249 Ma, and the metallogenic age of the Baolun gold deposit from 224.6+7.2 Ma. According to the geochemical characteristics of metamorphic basic rocks and the tectonic setting of the spikes, it is inferred that the metamorphic basic rocks occurred in the extensional tectonic environment during the post-collision stage. When the eastern segment of the Paleo-Tethys Ocean closed in Hainan Island, the oceanic crust subducted from north to South and entered the southern block, and was in the post-collision stage around 208-249 Ma. (4) The gold abundance analysis of metamorphic basic rocks shows that the gold abundance of some samples in the second group of metamorphic basic rocks is much higher than that of the crustal Clark value, and the data dispersion is large. Geochemical characteristics show that the magma of the second group of metamorphic basic rocks is an appropriate carrier for Au migration. Geochronological results show that the diagenetic age of metamorphic basic rocks is consistent with the metallogenic age of the Baolun gold deposit within the error range. Au. (5) Based on the above analysis, the model of occurrence of metamorphic basic rocks and gold mineralization in Baolun gold deposit should be that two metamorphic basic rocks occur successively under post-collision tectonic environment. Among them, a group of late-developed basic rocks carry Au from deep to shallow, and their basic magmatic hydrothermal fluid carries Au and other metallogenic elements and Au. The acidic magmatic hydrothermal mixtures of the Jianfeng intrusion migrate and rise along the fissures. The chemical properties of the ore-forming fluids are changed by the carbonaceous phyllite of the Silurian Tuoli Formation and the Tianshui percolated from the earth's surface. Au enrichment and mineralization occur. (6) This study shows that the metallogenic time of the Baolun gold deposit corresponds to the post-collisional stage of orogeny and the compressional direction. The adjacent peak-slip faults should be deep and large faults cutting through the continental lithosphere, and the Baolun gold deposit should be an orogenic gold deposit in combination with previous research results.
【學位授予單位】：中國科學院研究生院(廣州地球化學研究所)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P618.51
本文編號：2233187
[Abstract]:Baolun gold deposit is located in the southwest of Hainan Province, between the East-West spike-suspension fault and Jiusuo-Lingshui fault, and on the west side of the north-east Baisha fault. It is the largest high-grade gold deposit in Hainan Province at present. Control. During the study of Baolun gold deposit in Hainan Province, we found a large number of metamorphic basic rocks and gold veins closely associated in space. Based on the previous study of the deposit and on the basis of field geological survey, this paper carried out lithofacies and genetic mineralogy, whole rock geochemistry and Sm-Nd isotope composition. Based on the analysis and SHRIMP zircon U-Pb dating, and combined with the analysis of the whole rock gold abundance, the magmatic source area characteristics and occurrence tectonic setting of metamorphic basic rocks, and the relationship between these basic rocks and the mineralization of the Baolun gold deposit are discussed. The main achievements and understandings are as follows: (1) According to the field occurrence and geochemical characteristics, metamorphic basic rocks can be divided into metamorphic basic rocks. In the field occurrence, the first group occurs as fine veins, intermingled with strata, quartz veins, locally visible quartz and stratigraphic lenses; the second group metamorphic basic dikes are wider, larger, and more clean. In geochemical characteristics, the REEs content of the first group is 20-80 times higher than that of chondrites, and shows strong LREE enrichment. Negative anomalies with Eu (but slightly positive anomalies with BL-065 and 13BL-87), compared with N-MORB enrichment of Th, Ta, Nb and Ce, formed an intermediate "uplift" on the cobweb, and the values of epsilon Nd (230Ma) were mostly between - 6.62 and - 4.45; the second group of samples had relatively low REEs content, 14-40 times that of chondrites, mostly showing LREE depletion patterns (13BL-44). Except for positive anomalies (but slightly negative anomalies in 13BL-71) and Eu, the LIL elements such as Sr, K, Rb and Ba are enriched and the ratio of LIL to HFS is high relative to N-MORB, and the value of epsilon Nd (230 Ma) is distributed between 0.33 and 5.65. The main silicate minerals of the two groups of metamorphic basic rocks are plagioclase and amphibole, and the main metal minerals are magnetite, pyrite and chalcopyrite. Quartz appears in the metamorphic basic rocks, carbonate occurs locally, metallic minerals and a small amount of sphalerite. Residual pyroxene and altered minerals such as chlorite, epidote, epidote, sericite, biotite and carbonate can be found locally in the metamorphic basic rocks of the second group. (2) Geochemical characteristics show that although the magma source area of the first group is also deficient. The source area of the two groups of samples is shallow, and there is no residual garnet facies in the source area. The source area of the second group of samples may be affected by the water-bearing fluid in the subduction zone. The first group of samples were formed during the magmatic evolution process dominated by separation crystallization, and the mineral assemblage of separation crystallization was clinopyroxene + plagioclase + olivine. (3) By selecting zircons from metamorphic basic rocks for SHRIMP U-Pb dating, the diagenetic age of the second group of metamorphic basic rocks is 231.6+2.6 Ma, which is similar to the diagenetic age of the Jianfeng pluton from 208 to 249 Ma, and the metallogenic age of the Baolun gold deposit from 224.6+7.2 Ma. According to the geochemical characteristics of metamorphic basic rocks and the tectonic setting of the spikes, it is inferred that the metamorphic basic rocks occurred in the extensional tectonic environment during the post-collision stage. When the eastern segment of the Paleo-Tethys Ocean closed in Hainan Island, the oceanic crust subducted from north to South and entered the southern block, and was in the post-collision stage around 208-249 Ma. (4) The gold abundance analysis of metamorphic basic rocks shows that the gold abundance of some samples in the second group of metamorphic basic rocks is much higher than that of the crustal Clark value, and the data dispersion is large. Geochemical characteristics show that the magma of the second group of metamorphic basic rocks is an appropriate carrier for Au migration. Geochronological results show that the diagenetic age of metamorphic basic rocks is consistent with the metallogenic age of the Baolun gold deposit within the error range. Au. (5) Based on the above analysis, the model of occurrence of metamorphic basic rocks and gold mineralization in Baolun gold deposit should be that two metamorphic basic rocks occur successively under post-collision tectonic environment. Among them, a group of late-developed basic rocks carry Au from deep to shallow, and their basic magmatic hydrothermal fluid carries Au and other metallogenic elements and Au. The acidic magmatic hydrothermal mixtures of the Jianfeng intrusion migrate and rise along the fissures. The chemical properties of the ore-forming fluids are changed by the carbonaceous phyllite of the Silurian Tuoli Formation and the Tianshui percolated from the earth's surface. Au enrichment and mineralization occur. (6) This study shows that the metallogenic time of the Baolun gold deposit corresponds to the post-collisional stage of orogeny and the compressional direction. The adjacent peak-slip faults should be deep and large faults cutting through the continental lithosphere, and the Baolun gold deposit should be an orogenic gold deposit in combination with previous research results.
【學位授予單位】：中國科學院研究生院(廣州地球化學研究所)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P618.51
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，本文編號：2233187
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