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The alkali-feldspar phenocrysts in the two contrast Mesozoic granitic rockseries, binary mica-adamellite-granite series(S--type)and diorite-porphyriticgranodiorite-porphyritic granite series(I-type), of the area are very similarin many aspects. The phenocrysts are of large size, euhedral shape, and carlsbadtwin. The plagioclase and biotite inclusions in phenocrysts aligne paralleled withgrowth face of phenocrysts. Generally, the cores of phenocrysts are rich in plagi-oclase inclusions, but the quartz inclusions... The alkali-feldspar phenocrysts in the two contrast Mesozoic granitic rockseries, binary mica-adamellite-granite series(S--type)and diorite-porphyriticgranodiorite-porphyritic granite series(I-type), of the area are very similarin many aspects. The phenocrysts are of large size, euhedral shape, and carlsbadtwin. The plagioclase and biotite inclusions in phenocrysts aligne paralleled withgrowth face of phenocrysts. Generally, the cores of phenocrysts are rich in plagi-oclase inclusions, but the quartz inclusions only occurred in the rim. The Ab, An,Ba contents in phenocrysts are higher than in groudmass alkalifeldspars. Theforming temperature of the phenocrysts calculated from two-feldspar geothermo-meter of Whithey and Stormer(1977)are round 700℃, the X-rays reflectionsshow that most phenocrysts are intermediate orthoclase, the other a few areorthoclase and microcline. A1l the features above convince that the phenocrystsare crystalized from magma. Based on experimental data, the work also discu-ssed the crystalizing processes of the phenocrysts and it is considered that cry-stalized alkali-feldspar phenocrysts represent high water bontent of graniticmagma, 丹东地区两套中生代花岗岩系中许多岩体都含碱性长石斑晶。这些斑晶具有许多相似的性质,它们呈自形晶,粒度大,具卡氏双晶。其中斜长石、黑云母等包裹体平行斑晶的生长面而呈环状排列。通常核部附近的包裹物为斜长石,而石英反被包裹在斑晶的边缘。斑晶中Ab、An和钡的含量也较基质碱性长石高。由二长石温度计计算的斑晶生成温度为700℃左右。X—光衍射数据表明,斑晶主要为中间微外长石,少量为正长石和微斜长石,这些都说明了斑晶乃岩浆结晶产物。根据实验资料,还讨论了斑晶的结晶过程,并认为斑晶的晶出反映了岩浆高水压力的特点。 Two groups of feldspars——alkali feldspars and plagioclases, occur in six alkaline rockbodies of eastern China. The first group consisting of orthoclase, microcline and albite is dominant in all six rockbodies, while the second composed of andesine and oligoclase is only recognized in some of the rockbodies. There are three associations of feldspars, i. e., orthoclase-plagioclase, orthoclasemicrocline and albite-microcline making up perthite. In each of the associations feldspars exhibit some similarities in... Two groups of feldspars——alkali feldspars and plagioclases, occur in six alkaline rockbodies of eastern China. The first group consisting of orthoclase, microcline and albite is dominant in all six rockbodies, while the second composed of andesine and oligoclase is only recognized in some of the rockbodies. There are three associations of feldspars, i. e., orthoclase-plagioclase, orthoclasemicrocline and albite-microcline making up perthite. In each of the associations feldspars exhibit some similarities in composition or structure and the same compositional evolution trend of feldspars can be observed in some rockbodies. Based on the data on the structure state of feldspars and two-feldspar or feldspar-nepheline geothermometry, the forming temperatures of these rockbodies have been estimated. 我国东部六个碱性岩体的长石以碱性长石为主,包括了正长石、微斜长石和钠长石;斜长石有中长石和奥长石。它们具有三种组合,即正长石-斜长石;正长石-微斜长石;钠长石-微斜长石组成的条纹长石。各组合长石在组分或结构态方面都有某些共同之处,某些岩体还体现了长石成分演化的一致趋势。本文根据长石结构态,以及二长石和长石-霞石地质温度计的应用,对岩体形成温度作了一些探讨。 The Hercynian to Indosinian Darongshan granite belt is a typical example of peraluminous granites in South China. It is mainly composed of coarse-or intermediate-grained cordierite-biotite monzonitic granite(Darongshan body), intermediateor fine-grained porphyroid garnet-cordierite-biotite monzonitic granite (Jiuzhou body), and hypersthene granite porphyry with fine- or intermediate-grained phenocrysts (Taima body). In this paper, the relationship of magma crystallization temperatures of the three bodies is... The Hercynian to Indosinian Darongshan granite belt is a typical example of peraluminous granites in South China. It is mainly composed of coarse-or intermediate-grained cordierite-biotite monzonitic granite(Darongshan body), intermediateor fine-grained porphyroid garnet-cordierite-biotite monzonitic granite (Jiuzhou body), and hypersthene granite porphyry with fine- or intermediate-grained phenocrysts (Taima body). In this paper, the relationship of magma crystallization temperatures of the three bodies is discussed based on Al-Si order-disorder and cell parameters of feldspars, and the composition of biotites. P, T, f_(O2) and f_(H2O) for each granite body when the magma emplaced and crystallized are evaluated by means of estimating the thickness of the overlying strata, two-fieldspar geothermometer, homogenization temperaure of fluid inclusions in quartz, and biotite fugacity indicator. The results show that, for Darongshan body, the magma emplaced at a depth of 14~18.7km, crystallized at T=627~700℃, fo2 =5 10~(-16) bar and f_(H2O)=3.1kbar; for Jiuzhou body, the magma emplaced at a depth of 10~12km, crystallized at T=750-764℃, f_(O2)=10~(-14) bar and f_(H2O)=2.3kbar; for Taima body, the magma croplaced at 1.5~2.4km, crystallized at T=780~862℃, f_(O2) and f_(H2O) when biotite crystallized were 10~(-18) bar and 2.1kbar respectively. 根据钾长石与斜长石的结构状态和黑云的成分,得出岩带三个主要组成岩体岩浆结晶温度的定性变化规律。根据岩体侵入岩层的厚度、二长石地温计、熔体包裹体测温和黑云母逸度计,定量估算了岩浆定位结晶时的P、T、fO_2和fH_2O。估算结果表明,岩带岩浆定位条件差异大:P为4.86~0.4×10~8Pa,T从627至862℃,fO_2 5.01×10~(-11)~10~(-8)Pa,fH_2O2.06~3.11×10~8Pa。岩体定位条件的差异与不同岩体分别形成于钦州地槽褶皱回返的不同时期有关。
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