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Pillow lavas in Bompoka island of the Andaman–Nicobar islands, forming a part of Sunda–Burmese forearc, are composed of plagioclase and clinopyroxene microphenocrysts in a fine-grained ferruginous groundmass along with glass. They are also characterized by several quench plagioclase and clinopyroxene morphologies. Zr/TiO2 versus Nb/Y relationship of these pillow lavas show that these are tholeiitic basalts in composition. These basalts have low MgO (5.19–6.12 wt%), Ni (84–118 ppm), and Cr (144–175 ppm) abundance and high FeO(T)/MgO (1.71–1.92) ratios, reflecting their fractionated nature. In Th/Yb versus Nb/Yb and Ti/Yb versus Nb/Yb binary diagrams, they show N-MORB affinity. However, La/Nb–Y and Ce/Nb–Th/Nb relationships along with a slight LREE depleted (LaN/YbN = 0.75–0.82) pattern and high Ba/Zr (0.28–0.40) ratios and LILE (K, Rb, Ba, Sr and Th) enrichment relative to N-MORB, suggest their back-arc basin basalt affinity. It is inferred that these pillow basalts have been derived from a metasomatised N-MORB-like mantle source in a trench-distal (wider) back-arc basin, probably near the leading edge of the Eurasian continent during Early to Late Cretaceous times, prior to the currently active Andaman–Java subduction system. 相似文献
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O. S. Yakovleva I. V. Pekov L. Horváth I. A. Bryzgalov V. O. Yapaskurt E. V. Guseva 《Geology of Ore Deposits》2010,52(8):725-735
High-alumina fenites in the Mont Saint-Hilaire alkaline complex, Québec, Canada, form bodies at the contact of peralkaline
nepheline syenite. Fenites are subdivided into four types: corundum-spessartine-biotite-feldspar, muscovite-corundum-hercynite-biotite-feldspar,
carbonated muscovite-biotite-hercynite-feldspar, and spessartine-hercynite-feldspar. Accessory minerals of the ilmenite-pyrophanite
series, columbites, zircon, thorite, pyrrhotite, Fe, Mn, Mg, Ca, Ba, and REE carbonates, uedaite-(Ce), etc. are identified.
Three stages are suggested in the formation of these rocks. In mineralogy and geochemistry, the Mont Saint-Hilaire high-alumina
fenites are similar to Al-rich fenites replacing xenoliths in the Khibiny alkaline complex, Russia. In both cases, fenites
are related to peralkaline rocks and replace high-alumina protoliths: granite at Mont Saint-Hilaire and metapelites in the
Khibiny Mountains. These fenites are regarded as a specific type of fenites with rock-forming Mg-depleted hercynite. 相似文献
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The Tongfeng mercury zone is an important producer of mercury in China.The underlying Lower Cambrian black rock series is strongly depleted in mercury and is thought to be the major source bed for mercury mineralization .The Catian deposit ,as the representative of the zone, was formed at low temperature,which is characterized by a meteoric chlorine-rich and sulfur-poor ore-forming solution of high salinity.A geochemical genetic model of buried hydrothermal explosion is proposed. 相似文献
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The Khoshk River passes through Shiraz City, southwest Iran. It passes through the populated urban area of Shiraz and receives and carries different kinds of industrial and urban solid and liquid wastes produced by industries and domestic sewage. The obje… 相似文献