安徽栏杆含金刚石基性岩中石榴子石矿物学特征
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摘要
在中国东部皖北地区分布着新元古代镁铁质岩,其中一些碱性基性岩为金刚石的赋矿岩石。为了确定安徽栏杆金刚石矿区的石榴子石种类,对矿区内不同类型的石榴子石进行系统采样,测定了62件石榴子石微区化学成分。结果显示,安徽栏杆石榴子石矿物化学式A_3~(2+)B_2~(3+)(SiO_4)_3中的A组阳离子由Mg~(2+)、Fe~(2+)和Ca~(2+)离子占位,B主要由Al~(3+)、Fe~(3+)、Mn~(3+)和Cr~(3+)离子占位,三价阳离子主要为Al~(3+),二价阳离子主要为Ca~(2+),表明研究区石榴子石主要为钙铝-钙铁-镁铝石榴子石系列。在62个样品中,发现了超硅石榴子石。经过计算其形成的压力范围为12.1～12.8GPa,深度可达300km。
The mafic rock is exposed in northern Anhui Province,and some of them are diamondiferous rocks.In order to determine the type of garnets,the authors systematically sampled the garnets in diamondiferous basite in Lan'gan area.The MgO,SiO_2,FeO,TiO_2,Al_2O_3,Cr_2O_3,CaO,MnO values of 62 single crystal garnets in this area were measured by electron microprobe spectrometer.The results show that the chemical formula of garnet group minerals is A_3~(2+)B_2~(3+)(SiO_4)_3.Group A cations are composed of Mg~(2+),Fe~(2+)and Ca~(2+).Group B cations are composed of Al~(3+),Fe~(3+),Mn~(3+)and Cr~(3+).The trivalent cation is mainly Al~(3+)while divalent cation is mainly Ca~(2+).It is inferred that grossularite-andradite-almandine group is the primary class in the Lan'gan area.The high calcium silicate iron garnet(majorite)was found in 62 samples.According to the composition of these majorities in Lan'gan area,the garnet of the diamondiferous basite has formation pressure of 12.1～12.8GPa,and the depth is up to 300km.
The mafic rock is exposed in northern Anhui Province,and some of them are diamondiferous rocks.In order to determine the type of garnets,the authors systematically sampled the garnets in diamondiferous basite in Lan'gan area.The MgO,SiO_2,FeO,TiO_2,Al_2O_3,Cr_2O_3,CaO,MnO values of 62 single crystal garnets in this area were measured by electron microprobe spectrometer.The results show that the chemical formula of garnet group minerals is A_3~(2+)B_2~(3+)(SiO_4)_3.Group A cations are composed of Mg~(2+),Fe~(2+)and Ca~(2+).Group B cations are composed of Al~(3+),Fe~(3+),Mn~(3+)and Cr~(3+).The trivalent cation is mainly Al~(3+)while divalent cation is mainly Ca~(2+).It is inferred that grossularite-andradite-almandine group is the primary class in the Lan'gan area.The high calcium silicate iron garnet(majorite)was found in 62 samples.According to the composition of these majorities in Lan'gan area,the garnet of the diamondiferous basite has formation pressure of 12.1～12.8GPa,and the depth is up to 300km.
引文
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[22]Stachel T,Brey G P,Harris J W.Inclusions in sublithospheric diamonds:glimpses of deep Earth[J].Elements,2005,1(2):73-78.
[23]Roermund V,Herman L,Drury M R.Ultra-high pressure(P>6GPa)garnet peridotites in Western Norway:exhumation of mantle rocks from>185 km depth[J].Terra Nova,1998,10:295-301.
[24]Scambelluri M,Pettke T,Van Roermund H L M.Majoritic garnets monitor deep subduction fluid flow and mantle dynamics[J].Geology,2008,36(01):59-62.
[25]Collerson K D,Hapugoda S,Kamber B S,et al.Rocks from the Mantle Transition Zone:Majorite-Bearing Xenoliths from Malaita,Southwest Pacific[J].Science,2000,288(5469):1215-1223.
[26]Neal C R,Haggerty S E,Sautter V."Majorite"and"silicate perovskite"mineral compositions in xenoliths from Malaita[J].Science,2001,292(5519):1015.
[27]Ye K,Cong B,Ye D.The possible subduction of continental material to depths greater than 200km[J].Nature,2000,407:734-736.
[28]Song S,Zhang L,Niu Y.Ultra-deep origin of garnet peridotite from the North Qaidam ultrahigh-pressure belt,Northern Tibetan Plateau,NW China[J].American Mineralogist,2015,89(8/9):1330-1336.
[29]刘良,陈丹玲,张安达.阿尔金超高压(>7GPa)片麻状(含)钾长石榴辉石岩--石榴子石出溶单斜辉石的证据[J].中国科学(D辑),2005,35(02):105-114.
[30]牛贺才,张海祥,单强,等.扎河坝石榴辉石岩中超硅-超钛石榴子石的发现及其地质意义[J].科学通报,2007,(18):2169-2174.
[31]陆琦,刘惠芳,肖平,等.中国辽宁金刚石中高硅钙铁榴石(Majorite)等超高压矿物包裹体的发现及地质意义[J].地质科技情报,2012,31(5):1-7.
[32]Van Roermund H L M,Drury M R,Barnhoorn A,et al.Supersilicic garnet microstructures from an orogenic garnet peridotite,evidence for an ultra-deep(>6GPa)origin[J].Journal of Metamorphic Geology,2000,18(2):135-147.
[33]Joswig W,Stachel T,Harris J W,et al.New Ca-silicate inclusions in diamonds-tracers from the lower mantle[J].Earth and Planetary Science Letters,1999,173:1-6.
[34]Brenker F E,Vincze L,Vekemans B,et al.Detection of a Ca-rich lithology in the Earth's deep(>300km)convecting mantle[J].Earth and Planetary Science Letters,2005,236:579-587.
[2]黄先觉.金刚石原生矿床类型及安徽省金刚石找矿前景分析[J].安徽地质,2012,22(2):103-105.
[3]蔡逸涛,陈国光,张洁,等.安徽栏杆地区橄榄辉长岩地球化学特征及其与金刚石成矿的关系[J].资源调查与环境,2014,35(4):245-253.
[4]蔡逸涛,张洁.安徽栏杆含金刚石母岩岩石学研究[J].矿床地质2014,33(supp.):363-365.
[5]张岳桥,董树文.郯庐断裂带中生代构造演化史:进展与新认识[J].地质通报,2008,27(9):1371-1390.
[6]侯明金,王永敏,Mercier J,等.郯庐断裂带(安徽部分)动力学演化及其构造意义[J].地质通报,2003,22(2):36-43.
[7]姚仲伯.安徽省区域地质概要[J].中国区域地质,1986,(4):309-312.
[8]张洁,蔡逸涛,董钟斗,等.安徽栏杆金刚石矿物特征及其寄主母岩地球化学特征研究[J].宝石和宝石学杂志,2015,17(5):1-11.
[9]蔡逸涛,杨献忠,康丛轩.国内外金刚石成因认识现状[J].华东地质,2017,38(Supp.):95-102.
[10]Dawson J B,Stephens W E.Statistical Classification of Garnets from Kimberlite and Associated Xenoliths[J].The Journal of Geology,1975,83(5):589-607.
[11]Jamtvert B,Ragnarsdottir K,Wood B.On the origin of zoned grossular-andradite garnets in hydrothermal systems[J].European Journal of Mineralogy,1995,7(6):1399-1410.
[12]Jamtvert B,Wogelius R,Fraser D.Zonation patterns of skarn garnets-records of hydrothermal system evolution[J].Geology,1993,21(2):113-116.
[13]张安棣,谢锡林,郭立鹤.金刚石找矿指示矿物研究及数据库[M].北京:科学技术出版社,1991.
[14]Akaogi M,Akimoto S.Pyroxene-garnet solid-solution equilibria in the systems Mg4Si4O12-Mg3Al2Si3O12and Fe4Si4O12-Fe3Al2Si3O12at high pressures and temperatures[J].Physics of the Earth and Planetary Interiors,1977,15(1):90-106.
[15]Smith J V,Mason B.Pyroxene-Garnet Transformation in Coorara Meteorite[J].Science,1970,168(3933):832-833.
[16]Tappert R,Stachel T,Harris J W,et al.Subducting oceanic crust:The source of deep diamonds[J].Geology,2005,33(7):565-568.
[17]Ringwood A E,Major A,Ringwood A E,et al.High pressure transformations in pyroxenes[J].Earth Planet Science Letters,19661:351.
[18]Ringwood A E,Major A.Synthesis of majorite and other high pressure garnet and perovskites[J].Earth Planet Science Letters,1971,12:411-418.
[19]Ben H,Cayzer N.Decompression and unmixing of crystals included in diamonds from the mantle transition zone[J].Physics and Chemistry of Minerals,2007,34(9):647-656.
[20]Tappert R,Foden J,Stachel T,et al.Deep mantle diamonds from South Australia:A record of Pacific subduction at the Gondwanan margin[J].Geology,2009,37(1):43-46.
[21]Tappert R,Stachel T,Harris J W,et al.Mineral inclusions in diamonds from the Panda kimberlite,Slave Province,Canada[J].European Journal of Mineralogy,2005,17(3):423-440.
[22]Stachel T,Brey G P,Harris J W.Inclusions in sublithospheric diamonds:glimpses of deep Earth[J].Elements,2005,1(2):73-78.
[23]Roermund V,Herman L,Drury M R.Ultra-high pressure(P>6GPa)garnet peridotites in Western Norway:exhumation of mantle rocks from>185 km depth[J].Terra Nova,1998,10:295-301.
[24]Scambelluri M,Pettke T,Van Roermund H L M.Majoritic garnets monitor deep subduction fluid flow and mantle dynamics[J].Geology,2008,36(01):59-62.
[25]Collerson K D,Hapugoda S,Kamber B S,et al.Rocks from the Mantle Transition Zone:Majorite-Bearing Xenoliths from Malaita,Southwest Pacific[J].Science,2000,288(5469):1215-1223.
[26]Neal C R,Haggerty S E,Sautter V."Majorite"and"silicate perovskite"mineral compositions in xenoliths from Malaita[J].Science,2001,292(5519):1015.
[27]Ye K,Cong B,Ye D.The possible subduction of continental material to depths greater than 200km[J].Nature,2000,407:734-736.
[28]Song S,Zhang L,Niu Y.Ultra-deep origin of garnet peridotite from the North Qaidam ultrahigh-pressure belt,Northern Tibetan Plateau,NW China[J].American Mineralogist,2015,89(8/9):1330-1336.
[29]刘良,陈丹玲,张安达.阿尔金超高压(>7GPa)片麻状(含)钾长石榴辉石岩--石榴子石出溶单斜辉石的证据[J].中国科学(D辑),2005,35(02):105-114.
[30]牛贺才,张海祥,单强,等.扎河坝石榴辉石岩中超硅-超钛石榴子石的发现及其地质意义[J].科学通报,2007,(18):2169-2174.
[31]陆琦,刘惠芳,肖平,等.中国辽宁金刚石中高硅钙铁榴石(Majorite)等超高压矿物包裹体的发现及地质意义[J].地质科技情报,2012,31(5):1-7.
[32]Van Roermund H L M,Drury M R,Barnhoorn A,et al.Supersilicic garnet microstructures from an orogenic garnet peridotite,evidence for an ultra-deep(>6GPa)origin[J].Journal of Metamorphic Geology,2000,18(2):135-147.
[33]Joswig W,Stachel T,Harris J W,et al.New Ca-silicate inclusions in diamonds-tracers from the lower mantle[J].Earth and Planetary Science Letters,1999,173:1-6.
[34]Brenker F E,Vincze L,Vekemans B,et al.Detection of a Ca-rich lithology in the Earth's deep(>300km)convecting mantle[J].Earth and Planetary Science Letters,2005,236:579-587.