Low-pressure granulite facies metamorphism in the Larsemann Hills area, East Antarctica; petrology and tectonic implications for the evolution of the Prydz Bay area   总被引：4，自引：0，他引：4  

K. STÜWE  R. POWELL 《Journal of Metamorphic Geology》1989,7(4):465-483

ABSTRACT Thermobarometric studies on various granulite facies areas along the Prydz Bay coast, East Antarctica (73°-79°E, 68°-70°S), show that, at around 1100 Ma, during a late Proterozoic orogeny, the rocks of the Larsemann Hills suffered a lower pressure metamorphic peak than the surrounding areas. Along the Prydz Bay coast, the rocks affected by this event include parts of the Vestfold Hills block plus all of the Rauer Group, the Larsemann Hills and the Munro Kerr Mountains. The dykes in the south-west corner of the Vestfold Hills were recrystallized during this event with little deformation at temperatures not quite as high as in the areas further south-west (650°C, 6.5 kbar) (Collerson et al., 1983), the Rauer Group was metamorphosed at 800°C and 7.5 kbar (Harley, 1987a), the Larsemann Hills at 750°C and 4.5 kbar, and the Munro Kerr Mountains probably at around 850°C and 5 kbar. Retrograde equilibration in the different areas occurred during decompression to about 10 km depth in all areas, followed by isobaric cooling at this depth. This paper shows that the peak metamorphism in the Larsemann Hills occurred at a pressure which is too low to have been the consequence of thermal relaxation of overthickened crust with normal mantle heat flow. Although other areas in Prydz Bay were metamorphosed at sufficiently high pressures so that their decompression paths are not inconsistent with a continental collision model, the inferred pre-metamorphic peak histories and the requirement of consistency with the Larsemann Hills, make it unlikely that collision followed by erosion-driven decompression is an appropriate model. We suggest that the thermal regime of the crust in the Larsemann Hills region was controlled by a perturbation in the asthenosphere, with magma invasion of the crust. We suggest that the 500 Ma event, represented in Prydz Bay by granitic outcrops at Landing Bluff and by several K/Ar ages from the Larsemann Hills area, was responsible for the final excavation of the terrane.  相似文献   

Contrasting mineral parageneses in high-temperature calc-silicate granulites: examples from the Eastern Ghats, India   总被引：3，自引：0，他引：3  

S. DASGUPTA 《Journal of Metamorphic Geology》1993,11(2):193-202

Abstract Three types of mineral associations are described from calc-silicate granulites from the Eastern Ghats, India, where geothermobarometry in associated rocks suggests extremely high P–T conditions of metamorphism ( c . 9 ± 1 kbar, 950° C). These mineral associations are: (i) calcite + quartz + scapolite + plagioclase, (ii) calcite + scapolite + wollastonite + porphyroblastic garnet + coronal garnet and (iii) calcite + quartz + wollastonite + scapolite + porphyroblastic garnet + coronal garnet, all coexisting with K-feldspar, titanite and clinopyroxene. The first two associations evolved through nearly isobaric cooling retrograde paths, whereas the third evolved through a nearly isothermal decompression path followed by an isobaric cooling retrograde path. Textural and compositional characteristics suggest the following mineral reactions in the calc-silicate granulites: calcite + quartz = wollastonite + CO₂, calcite + plagioclase = scapolite, calcite + scapolite + wollastonite = porphyroblastic garnet ± quartz + CO₂, CaTs + wollastonite = coronal garnet (association ii) and wollastonite + scapolite = coronal garnet (association iii) + quartz + CO₂. Andradite content in garnet was buffered by the redox equilibria wollastonite + hedenbergite + O₂= andradite + quartz (association iii) and wollastonite + andradite + CaTs + scapolite = hedenbergite + calcite + grossular + O₂ (association ii). The contrasting mineral parageneses have been ascribed to interplay of variables such as X _CO2, f _O2, f _HCl in the fluid, bulk Na content and the nature of the retrograde P–T–X _CO2 paths through which the rocks evolved.  相似文献   

麻粒岩p—T—t轨迹的研究现状     

赖兴运 《地质科技情报》1993,12(4):22-26

综述了近年来麻粒岩中p-T-t轨迹的研究现状。内容涉及到麻粒岩相变质作用的温压条件及时间跨度,同时指出:结合岩石中的矿物组合、后成合晶及反应结构,利用矿物温压计是目前确定p-T-t轨迹的主要手段。  相似文献   

超高压变质作用研究现状及问题     

张立飞  崔文元 《地学前缘》1994,(Z1)

本文从超高压变质作用的矿物学、Ｐ－Ｔ－ｔ轨迹和超高压地体抬升、保存机制三个方面总结了近年来超高压变质作用研究所取得的重要进展和存在的问题。超高压变质作用的矿物学研究正在向深入发展，其Ｐ－Ｔ－ｔ轨迹具有三种成因类型。而其超高压地体的抬升、保存机制则是争论的焦点，其中增生楔模式（Ｐｌａｔｔ，１９８７）和连续俯冲─仰冲机制较好地解释了抬升过程，但也存在一些问题需进一步研究。  相似文献   

南极长城站至莫斯科和伊尔库茨克路径上时延的测量与传播路径研究          下载免费PDF全文

孙宪儒  王聚杰  杜军虎  杨维富 《极地研究》1994,6(1):61-65

本文介绍了利用在南极长城站接收来自ＲＷＭ（莫斯科）和ＲＩＤ（伊尔库茨克）台的授时信号的无线电波时延的测量方法，并依据１９９１年４月至１９９１年９月所测量的传播时延数据分析了电波传播路径。说明了沿长、短大圆路径的传播时段。判定存在着非大圆路径传播并阐明了关于非大圆路径传播的一些变化规律。对非大圆路径发生的条件进行了探讨  相似文献   

GPS工程控制网最优化设计的研究     

于来法  郑国宁 《测绘学院学报》1993,(4)

本文讨论了GPS工程控制网的最优化设计问题;通过对GPS工程控制网的精度和可靠性分析,建立了应用点位精度矩阵相关性优化GPS网的数学模型;针对解算中存在的问题,提出了最短路径法寻找整数变量线性规划问题的最优解。  相似文献   

应用地震资料设计水平井轨迹     

刘福贵  刘传虎 《地球物理学进展》1993,8(3):122-131

应用三维地震资料设计水平井的轨迹,用人工合成记录标定层位和岩性并进行精细的构造解释和储层横向预测,对测区速度场进行研究,利用Geoquest 人机联作解释系统编绘层拉平图、转弯测线剖面图,不整合面构造图,各套油层顶面构造图,沿地层倾向设计水平井的轨迹.经两口井钻探,钻遇不整合面的误差0.19%—0.39%,一口井平均钻遇油层204m,相当9口直井的效益.用地震资料设计巷道水平井的关键是油层标定、深度标定和确定油层走向,用人机联作系统绘制水平切片图、反射波振幅图、油层顶构造图,设计了在油层内钻探的巷道井.经钻探,钻遇不整合面的误差0.07%,在真厚度8.23m 的油层内钻进563m.  相似文献   

Metamorphism and granite genesis in the Hidaka Metamorphic Belt, Hokkaido, Japan   总被引：3，自引：0，他引：3  

Y. OSANAI  M. KOMATSU  M. OWADA 《Journal of Metamorphic Geology》1991,9(2):111-124

The Main Zone of the Hidaka Metamorphic Belt is an uplifted crustal section of island-arc type. The crust was formed during early Tertiary time, as a result of collision between two arc–trench systems of Cretaceous age. The crustal metamorphic sequence is divided into four metamorphic zones (I–IV), in which zone IV is in the granulite facies. A detailed study of the evolution of the Hidaka Belt, based on a revised P–T–t analysis of the metamorphic rocks, notably a newly found staurolite-bearing granulite, confirms a prograde isobaric heating path, after a supposed event of tectonic thickening of accretionary sedimentary and oceanic crustal rocks. During the peak metamorphic event (c. 53 Ma), the regional geothermal gradient attained 33–40° C km^?1, and the highest P–T condition obtained from the lowest part of the granulite unit is 830° C, 7 kbar. In this part, X_H2O of Gt–Opx–Cd gneiss is about 0.15 and that of Gt–Cd–Bt gneiss is 0.4. The P–T–X_H2O condition of the granulite unit is well within a field where fluid-present partial melting of pelitic and greywacke metamorphic rocks takes place. This is in harmony with the restitic nature of the Gt–Opx–Cd gneiss in the lowest part of the granulite unit. The possibility that partial melting took place in the Main Zone is significant for the genesis of the peraluminous (S-type) granitic rocks within it. The S-type granitic rocks in this zone are Opx–Gt–Bt tonalite in the granulite zone, Gt–Cd–Bt tonalite in the amphibolite zone, and Cd–Bt–Mus tonalite in the Bt–Mus gneiss zone. The mineralogical and chemical nature of these strongly peraluminous tonalitic rocks permit them to be regarded as having been derived from S-type granitic magma generated by crustal anatexis of pelitic metamorphic rocks in deeper crust.  相似文献   

多功能雾化室在ICP—AES中的应用研究     

吴联源  傅国民 《岩矿测试》1991,10(4):274-278

本文研究了一种多功能雾化室装置,以探索ICP-AES技术中溶液进样的新方式;并对雾化系统的主要参数进行测试,取得最佳的匹配条件。该雾化室装置包括旋流雾化、循环雾化和氢化-雾化等系统,可在同一操作条件下进行工作,适应多种分析的需要。并可任意选择合适的雾化射程来增强元素谱线强度的信背比和雾化的稳定性,以达到改善分析的精密度和检出限。  相似文献   

线性连续变化非弹性介质中地震波射线轨迹与走时研究     

赵国敏  白云  张中杰  滕吉文  孟补在  黄玉国 《华北地震科学》1994,(2)

地球内部非弹性介质广泛存在,垂向线性连续变化非弹性介质模型具有重要理论与实际意义,本文利用复速度概念推导得到了复速度随深度线性连续变化的非弹性介质中地震波射线轨迹与等时线方程.理论结果表明:在线性连续变化非弹性介质中,射线轨迹呈圆形,等时面的形状为椭圆.最后对射线轨迹与等时线方程的适用性条件进行了讨论.  相似文献