Provenance of Precambrian Fe- and Al-rich Metapelites in the Yenisey Ridge and Kuznetsk Alatau, Siberia： Geochemical Signatures

Major, trace and rare earth element contents of Fe- and Al-rich metapelites from the Korda （Yenisey Ridge） and Amar （Kuznetsk Alatau） formations were determined to examine the nature, origin and evolution of their protoliths. Results indicate that these rocks are the redeposited and metamorphosed products of Precambrian kaolinitic weathering crusts, while the geochemical distinctions between the studied metapelites are determined by different weathering conditions in the source area and tectonic settings. The protolith of the Korda Formation metapelites was produced by erosion products of the post-Archean granitoid rocks, which accumulated under humid climate conditions in shallow-water basins along the continental margin. The geochemical characteristics of the deeper primary deposits of the Amar Formation suggest that volcanogenic material of mafic composition derived from an island-arc environment had a major role in supplying the erosion zone. These results agree with lithofacies data and with the geodynamic reconstruction of the evolution of the Yenisey Ridge and Kuznetsk Alatau during the Mesoproterozoic and Neoproterozoic, respectively. It was shown that REEs had limited mobility during contact metamorphism. The coherent mobility of REEs during collisional metamorphism may be attributed both to mineral reactions responsible for modal changes and to local chemical heterogeneity inherited from the initial protolith.     

斜发沸石岩的阳离子交换性能——对钾离子选择吸附的研究

斜发沸石是天然沸石中较常见和具有实际应用价值的一种。其化学分子式为:Ca（Na·K）₄Al₆Si₃₀O₇₂·24H₂O。关于斜发沸石的吸附、阳离子交换等性能,国外已有很多研究,并已将天然的斜发沸石、丝光沸石应用于从空气中富集氧、石油化工、原子能放射性废水和工业污水的处理、干燥剂,土壤改良剂、造纸充填剂等许多方面。     

Zonal Metamorphic Complex in the Tongulack Mountain Ridge, Altai, Russia, and Explanation of Its Origin with the Help of Thermal Modelling

A moderate pressure / high temperature zonal metamorphic complex in the Tongulack Mountain Ridge, Altai, Russia, is described, and the applicability of the models of magmatic intrusion and fluid flow to explanation of its origin discussed. The Precambrian complex was formed at 500-700℃ and 3.0-5.5 kbars; it is a linear, 25-30 km wide, thermal anticline with a curved axis showing symmetric metamorphic zoning. The metamorphism was isochemical by its nature, as is corroborated by the chemical compositions of the rocks. Four zones can be recognized within the metamorphic complex: chloritic (on the peripheries), cordieritic, sillimanitic and staurolite-out (in the centre). The zones are separated by successive isograds: cordierite, staurolite-in or sillimanite and staurolite-out. It is argued that the origin of the metamorphic zoning can be explained best by a combined fluid-magmatic model; conductive heat flow from the intrusion predominated considerably over the fluid flux in heat transfer: the fluid flow     

广东河台金矿糜棱岩化过程构造-流体成矿研究

为了探讨糜棱岩化过程中的成矿作用,文章对广东河台金矿进行了构造流体过程的数值模拟研究。根据力的分解、显微构造及运动学涡度分析以及与模拟结果的对比,提出108°方向的双向挤压作用可能是本区糜棱岩化带形成时的力学环境。数值模拟结果结合前人研究成果表明,体积应变增量异常带有利于糜棱岩化和流体的聚集以及糜棱岩化过程中成矿作用的...     

热处理低温钠长石的EPR和X射线衍射研究

利用电子顺磁共振(EPR)和X射线衍射方法研究了天然和热处理钠长石单晶。热处理在500—850℃水热条件下完成。在外加磁场B平行于晶体c~*轴的方向上,测量了加热前后Fe~(3+)的EPR谱和线宽△B随温度和加热时间的变化。结果显示,线宽随Al、Si无序的增大而增加。由此得出结论,在低温钠长石中,Fe~(3+)位于Al~(3+)占据的T_1(o)位置,在被研究的温度范围内,Fe~(3+)未参与四面体位置T间Al、Si交换。谱线的加宽主要是由在Fe~(3+)邻近位置上Al、Si无序的增大引起的,同时与观测到的晶胞参数变化有关。在Al、Si无序更强的晶体中,Fe~(3+)谱变得极宽。     

Paleoproterozoic,High-Metamorphic,Metasedimentary Units of Siberian Craton

Abstract: Sensitive, high-resolution ion microprobe zircon U–Pb ages of Paleoproterozoic, high-grade, metasedimentary rocks from the south-western part of the Siberian Craton are reported. Early Precambrian, high-grade complexes, including garnet–biotite, hypersthene–biotite, and cordierite-bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4–3.1 Ga indicate Archean-to-Paleoproterozoic source provinces. Zircons from gneisses show core-rim textures in cathodoluminescence (CL) image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are: ≥2.7, ~2.3, and 1.95–2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga; therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High-grade metaterrigenous sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the Aldan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga (Wan et al., 2006). All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high-grade metamorphism was related to the consolidation of the Siberian Craton.     

我国东部白垩纪蚀变火山岩中的斜发沸石和丝光沸石

沸石是一种含水的碱和碱土金属的骨架状铝硅酸盐。由于沸石具有分子筛的作用,在应用中通常又将沸石称为分子筛。沸石作为催化剂、干燥剂、吸附剂和离子交换剂广泛地应用于工农业各个方面。天然沸石作为一种新型的矿物资源越来越为人们所重视。     

http://www.sciencedirect.com/science/article/pii/S1674987115000663

Mantle xenocrysts from early Triassic kimberlite pipes from Kharamai,Ary-Mastakh and Kuranakh fields in the Anabar shield of Siberia revealing similar compositional trends were studied to estimate the superplume influence on the subcratonic lithosphere mantle(SCLM).Pressure-temperature(PT) reconstructions using monomineral thermobarometry for 5 phases show division of the SCLM beneath the Kharamai field into 6 units:pyroxenitic Fe-rich(1-2 GPa) and Mg-rich(2-3 GPa) layers;middle with two levels of Gar-Sp pyroxenites at ~3 and 4-5 GPa;Gar-dunite-harzburgites ~4.5-6.5 GPa subjected to Ilm-Px vein metasomatism;and a Mg-rich dunite lower part.In the Anabar shield(Ary-Mastakh,Dyuken and Kuranakh fields) mantle lithosphere is composed of three large units divided into two parts:upper part with amphiboles and phlogopite;two levels of pyroxenites and eclogites at 3 and 4 GPa,and a lower part composed of refertilized dunites.Diagrams showing P-Fe~#Gar clusters for garnets and omphacites illustrate the differences between SCLM of these localities.Differences of Triassic SCLM from Devonian SCLM are in simple layering;abundance of Na-Cr-amphiboles and metasomatism in the upper SCLM part,thick pyroxenite-eclogite layer and lower part depletion,heated from SCLM base to 5.0 GPa.Kharamai mantle clinopyroxenes represent three geochemical types:(1) harzburgitic with inclined linear REE,HFSE troughs and elevated Th,U;(2) lherzolitic or pyroxenitic with round TRE patterns and decreasing incompatible elements;(3) eclogitic with Eu troughs,Pb peak and high LILE content.Calculated parental melts for garnets with humped REE patterns suggest dissolution of former Cpx and depression means Cpx and garnets extraction.Clinopyroxenes from Ary-Mastakh fields show less inclined REE patterns with HMREE troughs and an increase of incompatible elements.Clinopyroxenes from Kuranakh field show flatter spoon-like REE patterns and peaks in Ba,U,Pb and Sr,similar to those in ophiolitic harzburgites.The PT diagrams for the mantle sections show high temperature gradients in the uppermost SCLM accompanied by an increase of P-Fe~#Ol upward and slightly reduced thickness of the mantle keel of the Siberian craton,resulting from the influence of the Permian-Triassic superplume,but with no signs of delamination.     

成矿元素的气相迁移与实验研究

越来越多的野外观测和实验数据表明,气相对成矿元素的迁移和富集具有不可忽视的作用。由高温火山气体形成的升华壳和凝结水中富集多种岩浆组分和成矿金属;中低温的地热田水蒸气中也检测到成矿元素;某些斑岩型铜-金矿床的富气体包裹体比共存的盐水包裹体更富集Cu和Au。金属呈简单氯化物或氟化物、硫化物、含氧酸及原子迁移的理论假设低估了400℃以下气体搬运成矿金属的能力,而必须考虑溶剂化作用(水合作用),有关银、金、铜、锡、钼、钨在水热气相中的溶解度实验证实了这一点,基于实验数据的热力学模拟计算表明,水热气相可运移足够的成矿金属以形成具有经济价值的浅成热液型和斑岩型矿床。此外,实验也证实砷和硼从液相分配至气相中也与水合作用有关,其气液相间的分配系数随温度和水蒸气的压力增大而增强。无疑地,成矿金属被水热气相搬运的理论对理解金属矿床的形成机理和发展诸如深穿透地球化学的地球气找矿方法具有重要意义。     

山东昌乐蓝宝石的颜色成因与优化

本文对昌乐蓝宝石进行了大量的颜色指数测量。各样品的主波长虽多落在蓝紫—蓝—蓝绿区,但其纯度均很低,以致肉眼观察十分暗淡,近乎黑色。蓝宝石的颜色主要由全铁含量和Fe~(2+)/Fe~(3+)值决定。随Fe~(2+)含量的增多,蓝宝石的颜色由黄逐渐变为蓝紫色。热处理难以改变蓝宝石中全铁的含量,但可使不同价态铁的含量发生改变。昌乐蓝宝石中全铁含量太高,通常热处理效果不很理想。