Contrasting sapphirine parageneses from Wilson Lake, Labrador and their tectonic implications   总被引：7，自引：0，他引：7  

K.L. CURRIE  J. GITTINS 《Journal of Metamorphic Geology》1988,6(5):603-622

Abstract Regionally distributed pelitic granulites in the Wilson Lake region contain the assemblage sapphirine + hypersthene + sillimanite + quartz. Geochronology and geobarometry suggest it developed in early Proterozoic rocks at temperatures approaching 900°C and pressures above 10 kbar. Vein-like metasomatized rocks around a suite of mafic to ultramafic intrusions, emplaced near the peak of metamorphism about 1700 Ma ago, contain sapphirine, but these assemblages developed at temperatures near 750°C and pressures of 4.5 kbar. Both types of assemblage occur as relics in amphibolite-grade (biotite–sillimanite) migmatites.
P–T determinations indicate rapid isothermal uplift of 20 km accompanied by mafic intrusion and hydration. The metamorphic history and tectonic setting suggest exposure of deep continental crust by thrusting during continental collision, followed by essentially isothermal decompression.  相似文献   

利用石英375℃热释光峰研究其受热历史的模拟实验     

龚革联  蔡观强  刘顺生  夏斌 《地球化学》2007,36(6):633-637

岩石中的石英矿物由于本身晶体缺陷以及微量杂质的存在而具有热释光现象.石英的热释光现象取决于该矿物晶体内陷阱所捕获电子的热逸出并与复合中心复合而发光的效率,这些陷阱电子严格受到地质环境中随时间、空间条件而变化的环境温度场和辐射场的制约,即陷阱中所捕获的电子数是辐射充填过程和受热逸出过程这两种作用平衡后的结果.虽然地质条件下的温度场和辐射场随时间、空间变化的复杂性,使得完全获得地质体的温度变化历史几乎不可能,但是在实验室条件下,采用模拟试验的方法研究石英矿物的热释光信号在不同温度-时间激活条件下的衰退规律,并由此近似推断矿物经历的温度变化历史,却是可行的方法之一.利用石英矿物的375℃热释光峰的等温衰退特性,探讨其应用于石英矿物受热历史的实验研究,就是这样一种尝试.研究认为,采用实验室内等温热激活(isothermal activation)的方法,研究石英矿物375℃热释光峰的等温衰退变化规律,有可能定量或者半定量获得石英矿物宿主岩石的受热历史信息.  相似文献   

Petrology and isotopic evolution of granulites from central Madurai Block (southern India): reference to Ediacaran crustal evolution     

S. Tewari  M. K. Yadav  R. Yadav 《International Geology Review》2018,60(15):1792-1815

The Madurai Block, constituting part of the southern granulite terrain in southern India, has contributed significantly towards understanding the UHT (ultrahigh-temperature) granulites that serve as a window into the mid-lower continental crust. The dominant rock types are charnockites, sapphirine-bearing granulites, garnet cordierite gneisses, and quartzites. Significant textural relations reveal multiphase reactions responsible for the formation of diverse mineral parageneses during prolonged metamorphic history of the area. Prograde reaction is evident from the textural relationship where biotite/sillimanite relics are seen as inclusion in garnet/orthopyroxene, suggesting dehydration reactions. The symplectitic assemblages that formed during isothermal decompression involve a series of cordierite-forming reactions, followed by retrogression and cooling. Variety of mineral assemblages present in the rocks of this area offer a wide spectrum of P–T sensors that provide details on the physical conditions of metamorphism. For the rigorous interpretation of the P–T path in the Perumalmalai area, quantitative phase diagrams (P–T pseudosections) have been constructed and contoured for the compositional as well as modal isopleths of involved mineral phases. The rocks of Perumalmalai area document a clockwise decompression P–T trajectory, consistent with crustal thickening followed by extensional collapse. SHRIMP U–Pb ages from zircon associated with sapphirine-bearing granulite facies rocks of Perumalmalai area suggest a widespread Ediacaran tectonothermal event. The occurrence of Ediacaran UHT metamorphism followed by isothermal decompression in the Madurai Block is consistent with the timing and physical conditions associated with the formation of East African Orogen during the amalgamation of Gondwana.  相似文献   

三七炮弹的碘化银成核率检测          下载免费PDF全文

党娟  苏正军  房文  方春刚 《应用气象学报》2016,27(2):140-147

三七炮弹是进行人工增雨和防雹作业所需碘化银催化剂的主要载体之一,炮弹中碘化银催化剂的成核率数据是人工影响天气作业设计和指挥中进行催化剂作业剂量测算的重要参考,因此,对人工影响天气业务中使用的三七炮弹的碘化银成核率进行检测非常重要。2013年11—12月中国气象局人工影响天气中心利用新建的1200 L等温云室和钢板式20 m3专用爆炸室等设备,对目前人工影响天气业务中使用的两个厂家三七炮弹 (样品1、样品2) 的碘化银成核率进行国内首次统一检测。检测结果表明:两厂家炮弹成核率检测结果的拟合值量级均为109~1012/(g·AgI)(检测温度-6℃至-20℃),样品2成核率明显高于样品1。将本次检测结果与国内历次三七炮弹检测结果相比发现,两样品在负温高温段的成核率值均高于以往检测结果,其中,在具有指示意义的-10℃下的成核率,两样品均比以往检测结果要高2~3个量级。不同检测实验中成核率检测结果存在较大差异的现状说明,采用同一平台开展成核率统一检测十分必要。  相似文献   

内地核物质的状态参数及其量子效应的研究   总被引：1，自引：0，他引：1       下载免费PDF全文

刘植凤  李艳 《地球物理学进展》2008,23(2):438-442

采用与现有地震学数据一致的地核物质状态方程,计算了300K时压强-不可压缩系数的关系图,并与地核环境下PREM、PEM模型的数据加以比较;给出了内地核环境下温度-摩尔体积、温度-热压等参数的关系曲线,研究了地核物质的热学参数;应用计算所得到的热压值,借助量子统计物理的方法,列表给出了与内地核物质量子效应有关的各项参数.量子计算表明:巨大的地球自引力压强只是破坏了Fe原子的最外层和极少一部分Fe原子的次外层结构,并没有像白矮星一样使所有的核外电子发生全部的公有化.  相似文献   

煤储层条件下水分——平衡水分测定方法研究   总被引：3，自引：0，他引：3  

张庆玲 《煤田地质与勘探》1999,27(4):25-28

通过温度、粒度、时间等对平衡水分的影响实验,分析了各因素对平衡水分影响的原因,并在大量样品测试研究基础上,修改完善了平衡水分测定方法的技术参数,确定了实验的最佳条件,为等温吸附实验提供了准确、可靠的保证,并提出了相应的试验参数及误差范围。   相似文献   

利用巴克斯—吉尔伯特反演理论计算二维磁性体下界面     

刘天佑  宣霖康 《现代地质》1989,3(4):454

利用巴克斯—吉尔伯特反演理论实现了二度磁异常的下界面反演,针对重磁异常问题,讨论了获得稳定解的两种途径:奇异值截断法和加阻尼因子法,并以模型加以证实。  相似文献   

The hematite–goethite enhancement model of loess and an ‘irregular’ case from Paks,Hungary     

B. Bradk  Y. Seto  D. Csonka  T. Vgh  J. Szebernyi 《第四纪科学杂志》2019,34(4-5):299-308

On the basis of a key model of the appearance of hematite and goethite in some Chinese and European loess successions, paleosols generally contain higher proportions of hematite formed by pedogenic processes during warm and humid interglacials, while loess contains sedimentary goethite deposited during colder, glacial periods. Rock magnetic measurements were conducted on samples from Paks (Hungary) loess, revealing an anomalous case. Sediments were found to contain higher amounts of hematite and/or goethite, while the well‐developed paleosols were found to be lacking in hematite but had significant amounts of magnetite and maghemite. This observation demonstrates that the character of pedogenic magnetic mineral alteration and neoformation differs from the hematite/goethite model; the model is therefore not applicable to the Paks succession, possibly due to differences in the regional paleoclimate and pedogenic environment. The results indicate the existence of a further model, in which hematite formation is not significant in the course of pedogenesis.  相似文献   

北印度洋障碍层厚度气候态和季节变化特征及其成因初步分析     

刘颖  严幼芳  凌征 《热带海洋学报》2020,39(5):98-108

基于2004—2018年Argo (Array for Real-Time Geostrophic Oceanography)浮标观测的温度、盐度数据, 利用经验正交函数(EOF)分析和小波分析等方法对北印度洋(40°—105°E, 5°S—25°N)障碍层时空分布特征进行分析。结果显示: 北印度洋的东部常年存在障碍层, 而西部障碍层出现的概率相对较低; 较厚的障碍层出现在阿拉伯海东南部(67°—75°E, 3°—12°N)、孟加拉湾(82°—93°E, 11°—20°N)和赤道东印度洋(81°—102°E, 4°S—3°N)。阿拉伯海东南部和孟加拉湾障碍层厚度以年变化为主, 且呈同位相变化, 均为冬季最大, 夏季最小。赤道东印度洋区域则主要呈现半年周期变化, 在夏季和冬季各出现一次峰值。进一步分析表明, 孟加拉湾和赤道东印度洋障碍层厚度主要受等温层深度变化影响, 混合层深度变化对障碍层厚度变化的影响相对较小; 阿拉伯海障碍层厚度同时受等温层深度变化和混合层深度变化影响, 其中等温层深度变化对其影响更大。  相似文献   

Evaporites: Relative humidity control of primary mineral facies revisited     

Ibrahim M. Oroud 《水文研究》2019,33(3):395-404

It is widely accepted that the deposition of mineral facies of evaporite basins is controlled by the average annual relative humidity of the contiguous atmosphere, which dictates the equilibrium activity of the evaporating brine. This concept has far reaching implications in salt works and for the investigation of paleoenvironmental settings affecting depositional sequences within evaporite basins. The above concept, which dominated the scientific thought of evaporite basin investigations, suffers from two serious flaws: (a) the assumption of a static decoupled atmosphere and (b) the total neglect of energy input and thermodynamic feedbacks resulting from evaporation suppression. The present investigation will resolve the underlying mechanisms controlling the equilibrium activity of hypersaline solutions using a theoretical framework that combines energy and mass transport across the surface–atmosphere boundary. Calculations of the equilibrium activity of hypersaline solutions under isothermal conditions, as implied in the original concept, are not in line with the basic physical principles defining heat and mass exchange across the brine–atmosphere boundary and lead to substantial overestimation of actual evaporation and the activity itself. It is demonstrated that in addition to atmospheric relative humidity, the activity of hypersaline solutions is determined by numerous meteorological forcings along with hydrological, geochemical, and thermodynamic feedback mechanisms. Evaporation suppression resulting from a drop in brine activity causes substantial increase in brine temperature, which enhances vapour pressure differential across the interface, leading to more evaporation. This negative feedback shifts the brine activity downward for equilibrium to be attained. It is also demonstrated that evaporation from a brine surface usually proceeds when the relative humidity of the contiguous atmosphere is similar or even higher than that of the brine due to energy input and the strong negative feedback caused by evaporation suppression. The present investigation re‐establishes a new paradigm concerning the processes controlling evaporite basin sedimentation and palaeoclimate reconstruction as deduced from evaporite/hypersaline basin deposits. Findings have operational ramifications in the industrial applications of dissolved salt mineral extraction.  相似文献