贵州镇远马坪金伯利岩及其捕虏晶对金刚石成矿条件的指示意义
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摘要
贵州镇远是中国金刚石原生矿找矿的重点区域之一。镇远地区马坪D1号岩体是1965年中国首次发现的含原生金刚石金伯利岩。该岩体岩石具典型的金伯利岩结构和组成特征,其中的锆石捕虏晶U–Pb年代学和Hf同位素分析结果表明,该地区存在未暴露的太古宙基底物质残余。基于壳幔耦合性规律,可能对应有古老的岩石圈地幔,这种古老的克拉通属性是金刚石形成的有利因素。但另一方面,马坪金伯利岩普遍含有伴生矿物含铬镁铝榴石,其CaO含量较高,多数属于G9(二辉橄榄岩)类型,不是全球富含金刚石的方辉橄榄岩原岩类型(G10),暗示当时的岩石圈发生了部分改造而可能不利于高品质金刚石的形成。需要注意的是,在金刚石找矿过程中,应该以详细的野外工作与岩石学对比研究为基础,同时依赖于金伯利岩及其相关的岩浆活动所携带的捕虏体/捕虏晶的研究,配合以岩浆成分来反演地幔源区特征,才能较全面地揭示古老大陆岩石圈的形成年龄与演化历史、物质组成与精细结构,以及大陆岩石圈根的厚度、热状态、氧逸度、流体作用等,进而为寻找金刚石提供重要的依据。
Zhenyuan area of Guizhou Province is one of the key areas for diamond primary ore prospecting in China. In the Maping D1 rock mass of Zhenyuan area, the kimberlite occurrence with containing primary diamonds was discovered for the first time in1965. The rocks have structural and componential characteristics of typical kimberlites, the U-Pb geochronology and Hf isotope analyses of zircon xenocrysts entrained in the Maping D1 diamondiferous kimberlites indicate the existence of unexposed Archean basement remnants beneath the study area. Based on the regularity of crust-mantle coupling, with corresponding to the old lithospheric mantle, this nature of ancient craton is a favorable factor for diamond formation. On the other hand, the Maping kimberlites commonly contain associated minerals of Cr-pyrope with high CaO content, most of which belong to the G9(lherzolite)type rather than the global diamond-rich harzburgite protolith type(G10), suggesting that the state of lithosphere had been partly modified at that time and may not be conducive to the formation of high-quality diamonds. Note that in the processes of diamondprospecting, it should be based on the detailed field work and comparative petrological study, and rely on the investigation of diverse xenoliths/xenocrysts carried by kimberlites and the other associated magma activities, in combination with inversing the characteristics of mantle source by the composition of magmas. Therefore, it is possible to comprehensively reveal the ancient subcontinental lithosphere about the formation age and evolution history, material composition and fine structure, as well as the thickness, thermal state, oxygen fugacity, fluid activity and some other aspects of the subcontinental lithospheric root, thus providing important evidence for diamond prospecting.
Zhenyuan area of Guizhou Province is one of the key areas for diamond primary ore prospecting in China. In the Maping D1 rock mass of Zhenyuan area, the kimberlite occurrence with containing primary diamonds was discovered for the first time in1965. The rocks have structural and componential characteristics of typical kimberlites, the U-Pb geochronology and Hf isotope analyses of zircon xenocrysts entrained in the Maping D1 diamondiferous kimberlites indicate the existence of unexposed Archean basement remnants beneath the study area. Based on the regularity of crust-mantle coupling, with corresponding to the old lithospheric mantle, this nature of ancient craton is a favorable factor for diamond formation. On the other hand, the Maping kimberlites commonly contain associated minerals of Cr-pyrope with high CaO content, most of which belong to the G9(lherzolite)type rather than the global diamond-rich harzburgite protolith type(G10), suggesting that the state of lithosphere had been partly modified at that time and may not be conducive to the formation of high-quality diamonds. Note that in the processes of diamondprospecting, it should be based on the detailed field work and comparative petrological study, and rely on the investigation of diverse xenoliths/xenocrysts carried by kimberlites and the other associated magma activities, in combination with inversing the characteristics of mantle source by the composition of magmas. Therefore, it is possible to comprehensively reveal the ancient subcontinental lithosphere about the formation age and evolution history, material composition and fine structure, as well as the thickness, thermal state, oxygen fugacity, fluid activity and some other aspects of the subcontinental lithospheric root, thus providing important evidence for diamond prospecting.
引文
[1]池际尚,路凤香,刘永顺,等.中国原生金刚石成矿地质条件研究[M].武汉:中国地质大学出版社,1996:1-144.
[2]郑建平,路凤香,赵磊,等.华北地台古生代金伯利岩(包括金刚石)中流体及其在地幔演化中的作用[J].大地构造与成矿学1996,20(2):105-118.
[3]郑建平,路凤香.古地幔流体及其在大陆克拉通地幔演化中的意义--以华北地台为例[J].地学前缘,1996,3(3/4):187-194.
[4]郑建平,路凤香.华北地台东部金伯利岩源区反演及其不均一性探讨[J].长春地质学院学报,1997,27(2):135-140.
[5]Tappe S,Smart K,Torsvik T,et al.Geodynamics of kimberlites on a cooling earth:Clues to plate tectonic evolution and deep volatile cycles[J].Earth and Planetary Science Letters,2018,484:1-14.
[6]Tappe S,Kjarsgaard B A,Kurszlaukis S,et al..Petrology and NdHf isotope geochemistry of the Neoproterozoic Amon kimberlite sills,Baffin Island(Canada):Evidence for deep mantle magmatic activity linked to supercontinent cycles[J].Journal of Petrology,2014,55(10):2003-2042.
[7]Foley S F.A reappraisal of redox melting in the earth's mantle as a function of tectonic setting and time[J].Journal of Petrology,201152(7/8):1363-1391.
[8]Stern R J,Leybourne M I,Tsujimori T.Kimberlites and the start of plate tectonics[J].Geology,2016,44:799-802.
[9]Mitchell R H(喻学惠,胡海燕,薛君治,译).金伯利岩[M].武汉中国地质大学出版社,1991:1-285.
[10]王砚耕.贵州构造基本格架及其特征[C]//贵州区域构造矿田构造学术讨论论文集.贵阳:贵州科技出版社,1992:12-16.
[11]王砚耕.贵州主要地质事件与区域地质特征[J].贵州地质,199613(2):99-104.
[12]戴传固,胡明扬,陈建书,等.贵州重要地质事件及其地质意义[J].贵州地质,2015,32:1-9.
[13]马大铨,赵子杰,徐涛,等.贵州马坪云母金伯利岩及伴生偏碱性超基性岩的岩石特征[J].中国地质科学院宜昌地质矿产研究所所刊,1983,7:65-75.
[14]罗会文,杨光树,盛学庸.我国的第一批含金刚石金云火山岩--为贵州已知的含金刚石岩石正名[J].贵州地质,1994,11(1):8-26.
[15]郑建平,路凤香,叶德隆.金伯利岩中金刚石多源性标志[J].地质科技情报,1991,10(增刊):63-69.
[16]路凤香,郑建平,陈美华.有关金刚石形成条件的讨论[J].地学前缘,1998,5(3):125-131.
[17]路凤香,赵磊,邓晋福,等.华北地台金伯利岩岩浆活动时代讨论[J].岩石学报,1995,11(4):365-374.
[18]路凤香.地幔的窗口:金刚石[J].自然杂志,2010,33(3):161-165.
[19]郑建平,路凤香,郭晖,等.金刚石中流体包裹体的研究[J].科学通报,1994,39(3):253-256.
[20]郑建平,余淳梅,路凤香,等.不连续生长的金刚石与克拉通地块内部增生过程中的地幔流体作用[J].地学前缘,2001,8(3):103-109.
[21]郑建平,路凤香.华北地台深部地幔流体的组成--来自金刚石不纯净组分的报道[J].地质科学,1998,33(1):51-60.
[22]郑建平,路凤香,成中梅,等.金刚石的不纯净组分与地幔流体的研究[J].地质科技情报,1995,14(2):52-56.
[23]黄远成,李志翔,丘志力,等.贵州镇远钾镁煌斑岩原生及砂矿金刚石矿物学特征及其找矿意义[J].中山大学学报,2016,55(5):108-118.
[24]刘观亮,汪雄武.Ⅱ型金刚石形成的地质条件探讨[J].中国地质科学院宜昌地质矿产研究所所刊,1989,14:41-81.
[25]梅厚钧,唐春景,李荪蓉,等.中国的钾镁煌斑岩和金伯利岩与金刚石矿床生成[J].中国科学(D辑),1998,28(增刊):71-77.
[26]孙士军,杨松平.贵州金刚石成矿条件初探[J].贵州地质,1998,15:1-8.
[27]路凤香.金伯利岩与金刚石[J].自然杂志,2008,30(2):63-66.
[28]张舟,张宏福.金刚石与深部碳循环[J].地学前缘,2011,18(3):268-283.
[29]郑建平.辽东金伯利岩成因研究的某些进展[J].地质科技情报,1989,8(2):8-14.
[30]徐涛.贵州马坪和湖北彭家塝金伯利岩中的锆石[J].中国地质科学院宜昌地质矿产研究所所刊,1982,5:28-39.
[31]Zheng J P,Griffin W L,O’Reilly S Y,et al..Widespread Archean basement beneath the Yangtze Craton[J].Geology,2006,34(6):417-420.
[32]郑建平.不同时空背景幔源物质对比与华北深部岩石圈破坏和增生置换过程[J].科学通报,2009,54(14):1990-2007.
[33]戴传固,郑启钤,陈建书,等.贵州雪峰-加里东构造旋回期成矿地质背景研究[J].地学前缘,2013,20:219-225.
[34]马大铨.中国东部金伯利岩体中镁铝榴石的对比研究及其形成条件的讨论[J].中国地质科学院宜昌地质矿产研究所所刊,1980,1:26-38.
[35]郑建平,路凤香,O’Reilly S Y,等.华北地台东部古生代与新生代岩石圈地幔特征及其演化[J].地质学报,1999,73(1):47-56.
[2]郑建平,路凤香,赵磊,等.华北地台古生代金伯利岩(包括金刚石)中流体及其在地幔演化中的作用[J].大地构造与成矿学1996,20(2):105-118.
[3]郑建平,路凤香.古地幔流体及其在大陆克拉通地幔演化中的意义--以华北地台为例[J].地学前缘,1996,3(3/4):187-194.
[4]郑建平,路凤香.华北地台东部金伯利岩源区反演及其不均一性探讨[J].长春地质学院学报,1997,27(2):135-140.
[5]Tappe S,Smart K,Torsvik T,et al.Geodynamics of kimberlites on a cooling earth:Clues to plate tectonic evolution and deep volatile cycles[J].Earth and Planetary Science Letters,2018,484:1-14.
[6]Tappe S,Kjarsgaard B A,Kurszlaukis S,et al..Petrology and NdHf isotope geochemistry of the Neoproterozoic Amon kimberlite sills,Baffin Island(Canada):Evidence for deep mantle magmatic activity linked to supercontinent cycles[J].Journal of Petrology,2014,55(10):2003-2042.
[7]Foley S F.A reappraisal of redox melting in the earth's mantle as a function of tectonic setting and time[J].Journal of Petrology,201152(7/8):1363-1391.
[8]Stern R J,Leybourne M I,Tsujimori T.Kimberlites and the start of plate tectonics[J].Geology,2016,44:799-802.
[9]Mitchell R H(喻学惠,胡海燕,薛君治,译).金伯利岩[M].武汉中国地质大学出版社,1991:1-285.
[10]王砚耕.贵州构造基本格架及其特征[C]//贵州区域构造矿田构造学术讨论论文集.贵阳:贵州科技出版社,1992:12-16.
[11]王砚耕.贵州主要地质事件与区域地质特征[J].贵州地质,199613(2):99-104.
[12]戴传固,胡明扬,陈建书,等.贵州重要地质事件及其地质意义[J].贵州地质,2015,32:1-9.
[13]马大铨,赵子杰,徐涛,等.贵州马坪云母金伯利岩及伴生偏碱性超基性岩的岩石特征[J].中国地质科学院宜昌地质矿产研究所所刊,1983,7:65-75.
[14]罗会文,杨光树,盛学庸.我国的第一批含金刚石金云火山岩--为贵州已知的含金刚石岩石正名[J].贵州地质,1994,11(1):8-26.
[15]郑建平,路凤香,叶德隆.金伯利岩中金刚石多源性标志[J].地质科技情报,1991,10(增刊):63-69.
[16]路凤香,郑建平,陈美华.有关金刚石形成条件的讨论[J].地学前缘,1998,5(3):125-131.
[17]路凤香,赵磊,邓晋福,等.华北地台金伯利岩岩浆活动时代讨论[J].岩石学报,1995,11(4):365-374.
[18]路凤香.地幔的窗口:金刚石[J].自然杂志,2010,33(3):161-165.
[19]郑建平,路凤香,郭晖,等.金刚石中流体包裹体的研究[J].科学通报,1994,39(3):253-256.
[20]郑建平,余淳梅,路凤香,等.不连续生长的金刚石与克拉通地块内部增生过程中的地幔流体作用[J].地学前缘,2001,8(3):103-109.
[21]郑建平,路凤香.华北地台深部地幔流体的组成--来自金刚石不纯净组分的报道[J].地质科学,1998,33(1):51-60.
[22]郑建平,路凤香,成中梅,等.金刚石的不纯净组分与地幔流体的研究[J].地质科技情报,1995,14(2):52-56.
[23]黄远成,李志翔,丘志力,等.贵州镇远钾镁煌斑岩原生及砂矿金刚石矿物学特征及其找矿意义[J].中山大学学报,2016,55(5):108-118.
[24]刘观亮,汪雄武.Ⅱ型金刚石形成的地质条件探讨[J].中国地质科学院宜昌地质矿产研究所所刊,1989,14:41-81.
[25]梅厚钧,唐春景,李荪蓉,等.中国的钾镁煌斑岩和金伯利岩与金刚石矿床生成[J].中国科学(D辑),1998,28(增刊):71-77.
[26]孙士军,杨松平.贵州金刚石成矿条件初探[J].贵州地质,1998,15:1-8.
[27]路凤香.金伯利岩与金刚石[J].自然杂志,2008,30(2):63-66.
[28]张舟,张宏福.金刚石与深部碳循环[J].地学前缘,2011,18(3):268-283.
[29]郑建平.辽东金伯利岩成因研究的某些进展[J].地质科技情报,1989,8(2):8-14.
[30]徐涛.贵州马坪和湖北彭家塝金伯利岩中的锆石[J].中国地质科学院宜昌地质矿产研究所所刊,1982,5:28-39.
[31]Zheng J P,Griffin W L,O’Reilly S Y,et al..Widespread Archean basement beneath the Yangtze Craton[J].Geology,2006,34(6):417-420.
[32]郑建平.不同时空背景幔源物质对比与华北深部岩石圈破坏和增生置换过程[J].科学通报,2009,54(14):1990-2007.
[33]戴传固,郑启钤,陈建书,等.贵州雪峰-加里东构造旋回期成矿地质背景研究[J].地学前缘,2013,20:219-225.
[34]马大铨.中国东部金伯利岩体中镁铝榴石的对比研究及其形成条件的讨论[J].中国地质科学院宜昌地质矿产研究所所刊,1980,1:26-38.
[35]郑建平,路凤香,O’Reilly S Y,等.华北地台东部古生代与新生代岩石圈地幔特征及其演化[J].地质学报,1999,73(1):47-56.