岩石中矿物的关系

岩石中矿物的关系野外产状和手标本特征是岩相学最重要的工作基础镜下工作：

(1)镜下有什么：即由哪些矿物组成？各种矿物的相对多少？以确定岩石的名称

(2)镜下矿物之间的相互关系：

同种矿物（时间关系，确定不同的世代）不同种矿物（空间关系）

(3)矿物之间复杂关系所反映的岩石演化历史：

以主期矿物作为基准，残余矿物－早期矿物内部包裹裂隙中的矿物－－后期填充出溶矿物－－早期残余或后期变化反应边外部变化后成合晶重结晶部分熔融或残余岩浆后的结晶黄尾河榴辉岩

主要由石榴子石、绿辉石、金红石组成，同时还有后期退变矿物：斜长石、角闪石、尖晶石、橄榄石、斜方辉石等。GarnetPl+AmpSp+Ol+PlOlPlSp石榴石的退变质反应（a)Garnet－－→Ol+Sp+Pl(2)

榴辉岩相麻粒岩相(b)Ol+Sp+Pl(2)－→Pl（1)＋Amp麻粒岩相角闪岩相EnstatiteOl+Silica（游离态）－→Enstatite（a)Garnet－－→En+Sp+Pl(2)

榴辉岩相麻粒岩相(b)En+Sp+Pl(2)－→Pl（1)＋Amp麻粒岩相角闪岩相三个阶段榴辉岩相：石榴石麻粒岩相:尖晶石+橄榄石+斜长石尖晶石+顽火辉石+斜长石角闪岩相:斜长石+角闪石图１黄尾河榴辉岩中的绿辉石单斜辉石中的电子探针分析及计算结果SampleNo.InclusioningarnetInclusioninapatite

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Wt％oxidesSiO255.7254.6953.9453.2752.8853.2654.5956.3356.21TiO20.090.090.090.070.090.070.090.070.07Al2O34.184.024.093.883.923.884.054.194.18Cr2O30.050.030.070.050.030.050.050.050.07FeO5.766.215.968.027.758.446.785.655.63MnO0.030.000.050.140.080.190.030.030.05MgO12.2712.9413.7113.9512.8713.7513.8512.2012.52CaO17.8617.2617.7118.1418.4117.0516.7416.5218.01Na2O4.393.794.002.813.212.634.064.354.28K2O0.010.020.020.010.010.010.010.020.01Total100.3699.0599.64100.3499.2599.33100.2599.41101.03

CationspersixoxygenatomsSi1.9991.9941.9541.9381.9451.9601.9672.0272.002Altotal0.1770.1730.1750.1660.1700.1680.1720.1780.176AlⅣ0.0010.0060.0460.0620.0550.0400.0330.0000.000AlⅥ0.1760.1670.1290.1050.1150.1280.1390.1780.176Fe2+0.1750.1910.1830.2460.2410.2610.2070.1720.169Mg0.6560.7030.7400.7560.7060.7540.7440.6540.665Ca0.6860.6740.6870.7070.7260.6720.6460.6370.687Na0.3050.2860.2810.1980.2290.1880.2840.3030.296∑cations4.0014.0064.0244.0194.0214.0124.0223.9743.998续上表CaTs0.10.64.66.25.54.03.30.00.0Jd30.528.628.119.822.918.828.430.329.6CaEs-13-12.5-19.8-15.5-16.9-10-17.8-12.5-12Aug68.466.259.558.361.659.258.063.768.7Opx7.411.616.430.016.621.218.69.47.4续上表

CationspersixoxygenatomsSi1.9981.9931.9761.9781.9921.9721.9811.9791.9181.891Altotal0.1960.2120.2100.1990.2030.2020.2050.2110.1950.193AlⅣ0.0020.0070.0240.0220.0080.0280.0190.0210.0820.109AlⅥ0.1940.2040.1860.1770.1950.1740.1860.1910.1140.084Fe2+0.1780.1750.1810.1790.1760.1850.1880.1850.2670.311Mg0.6730.6880.6980.7010.6870.7040.7050.6910.8060.838Ca0.7370.7190.7240.7370.7230.7320.7230.7240.7420.718Na0.2160.2090.2150.2070.2110.2050.1980.2080.0840.053CaTs0.20.72.42.20.82.81.92.18.210.9Jd21.620.921.520.721.120.519.820.88.45.3CaEs-2.4-1.2-5.3-5.2-2.4-5.9-3.1-3.8-5.3-7.8Aug73.771.972.473.772.373.272.372.457.861.8Opx5.77.27.87.27.07.98.57.624.821.6绿辉石的边缘：后成合晶绿辉石的退变质反应：

－－边缘的后成合晶(a)Omphacite－→Pl(1)＋{Amp}

榴辉岩相角闪岩相(b){Amp}－→Ens+Sp

角闪岩相麻粒岩相Omphacite→Pl(1)＋{Amp}→Pl(1)+Ens+Sp榴辉岩相

角闪岩相麻粒岩相绿辉石中出溶包裹体的化学组成NoSiO2TiO2Al2O3Cr2O3FeOMnOMgOCaONa2OK2OTotMin198.560.030.040.000.180.000.320.420.210.0099.76Quar-tz298.930.010.020.000.100.000.210.240.170.0099.68368.240.0618.720.000.520.000.381.3410.420.0099.68Feld-spar467.460.0013.760.031.500.003.056.237.750.0099.78564.850.0016.640.080.750.001.612.687.174.1497.84669.940.0710.750.001.430.003.065.723.180.0094.23重新计算的长石包裹体的化学组成

NO.SiO2Al2O3FeOCaONa2OK2O

Mol％QzOrAbAn368.9219.220.360.8110.690.0018.850.0077.903.25471.7116.800.092.109.300.0039.230.0054.036.74563.6021.480.000.319.065.549.8525.5363.431.19681.1413.840.001.523.490.0087.260.0010.272.47具有出溶包裹体的单斜辉石组成MantleAnalysedwithbroadbeam

Analysedwithsmallbeam(～μm)Core-------------Mantle------------------RimSampleNo.12345678910

wt％oxidesSiO254.6254.7354.4854.4054.8254.1854.4854.2051.5250.79TiO20.100.060.050.090.110.210.070.070.140.05Al2O34.544.934.904.644.754.704.784.914.454.39Cr2O30.050.080.020.040.160.010.030.020.020.03FeO5.805.755.955.875.786.066.176.068.579.93MnO0.000.040.060.050.040.000.000.110.160.16MgO12.3512.6812.9112.9412.6912.9813.0112.6914.5215.10CaO18.8118.4418.6218.9118.5818.7718.5618.4918.5918.01Na2O3.052.963.052.933.002.902.812.941.160.73K2O0.000.000.000.020.000.010.000.000.000.00Total99.3299.69100.0499.8999.9399.8299.8699.4999.1399.19绿辉石的退变质反应

－－残留的绿辉石的出溶绿辉石（次）透辉石+石英+富钠长石麻粒岩相分解反应:绿辉石透辉石+石英+长石严格来说是分解反应，关键在于绿辉石中六配位的Al由于温度的升高而变成四配位的Al，从而在T位取代Si，因此有游离的石英析出。这应该是麻粒岩相时的高温反应。绿辉石的退变质反应(a)Garnet－－→Plagioclase（1)＋Amp

榴辉岩相角闪岩相(b)Pl(1)＋Amp－→Ol+Sp+Pl(2)

角闪岩相麻粒岩相

Ol+Silica－→Enstatite（a)Garnet－－→Ol+Sp+Pl(2)

榴辉岩相麻粒岩相(b)Ol+Sp+Pl(2)－→Pl（1)＋Amp麻粒岩相角闪岩相Route2Route1结论三个阶段榴辉岩相

:石榴石+绿辉石角闪岩相:斜长石+角闪石麻粒岩相:尖晶石+橄榄石+斜长石尖晶石+顽火辉石+斜长石透辉石+石英+富钠长石北大别榴辉岩退变质过程北大别榴辉岩岩相学特征表明榴辉岩在折返