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A.M.R. Neiva 《Chemical Geology》1974,13(4):295-308
Greisenization of a muscovite-biotite albite granite of Alijó-Sanfins, northern Portugal, is studied for both major and trace elements. The principal tin-tungsten mineralization of the region is connected with this granite and the greisenization is accompanied by an increase in Cl, F, W, Nb, Sn, Pb and Rb. Cassiterite is the main carrier of Sn. Muscovite is the concentrator of Cl and F. The muscovite of the greisenized granite contains more Cl, F, W and Nb than the muscovite of the parental granite, but the former contains less Sn. Sn content of the muscovite of the greisenized granite is higher than that of the biotite of the parental granite; W content is similar or higher.When the greisenization is accompanied by albitization, the oxides and trace elements behave in a similar way to that found only with greisenization, except that there is a decrease of Ni and Rb. Li, Zr, Sr, Ba and Rb decrease as albitization increases. 相似文献
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The Rio Espinharas pluton, northeastern Brazil, belongs to the shoshonitic series and consists mainly of syenogranite, quartz–monzonite and porphyritic quartz–monzonite, but diorite, quartz–monzodiorite, quartz–syenite and microsyenogranite also occur containing microgranular enclaves, except for the diorite. Most variation diagrams of rocks, amphiboles, biotites and allanites show linear trends, but K, Zr, Sr and Ba of rocks display curved scattered trends. The rocks ranging from diorite to syenogranite define a pseudo-errorchron and have similar REE patterns. Syenogranite and microsyenogranite are derived from two distinct pulses of granite magma with initial 87Sr/86Sr ratio of 0.7083±0.0003 and 0.7104±0.0007, respectively. Modelling of major and trace elements shows that the syenogranite evolved by fractional crystallization of plagioclase, microcline, edenite, biotite and titanite, whereas quartz–monzonite, porphyritic quartz–monzonite, quartz–monzodiorite and quartz–syenite resulted from simple mixing between an upper mantle-derived dioritic magma and the upper crust-derived syenogranite magma. Dioritic enclaves are globules of a mafic magma from the upper mantle. 相似文献
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Paula C.S. Carvalho Ana M.R. Neiva Maria M.V.G. Silva Eduardo A. Ferreira da Silva 《Chemie der Erde / Geochemistry》2014
Waters from abandoned Sb-Au mining areas have higher Sb (up to 2138 μg L−1), As (up to 1252 μg L−1) and lower Al, Zn, Li, Ni and Co concentrations than those of waters from the As-Au mining area of Banjas, which only contain up to 64 μg L−1 As. In general, Sb occurs mainly as SbO3− and As H2AsO4−. In general, waters from old Sb-Au mining areas are contaminated in Sb, As, Al, Fe, Cd, Mn, Ni and NO2−, whereas those from the abandoned As-Au mining area are contaminated in Al, Fe, Mn, Ni, Cd and rarely in NO2−. Waters from the latter area, immediately downstream of mine dumps are also contaminated in As. In stream sediments from Sb-Au and As-Au mining areas, Sb (up to 5488 mg kg−1) and As (up to 235 mg kg−1) show a similar behaviour and are mainly associated with the residual fraction. In most stream sediments, the As and Sb are not associated with the oxidizable fraction, while Fe is associated with organic matter, indicating that sulphides (mainly arsenopyrite and pyrite) and sulphosalts containing those metalloids and metal are weathered. Arsenic and Sb are mainly associated with clay minerals (chlorite and mica; vermiculite in stream sediments from old Sb-Au mining areas) and probably also with insoluble Sb phases of stream sediments. In the most contaminated stream sediments, metalloids are also associated with Fe phases (hematite and goethite, and also lepidocrocite in stream sediments from Banjas). Moreover, the most contaminated stream sediments correspond to the most contaminated waters, reflecting the limited capacity of stream sediments to retain metals and metalloids. 相似文献