ABSTRACT
Zircon is a very common accessory mineral in intermediate to felsic igneous rocks
and one of the most resistant mineral to metamorphic, hydrothermal and weathering
processes. It´s high chemical stability, associated with the presence of characteristic
trace elements in their internal structure, such as Hf, Y, Nb, Th, and U, may be useful
in identifying the nature of its original magma and in the characterization of magmatic
fractionation processes. Zircon crystals of tin-granites have low Zr/Hf ratios, and are
enriched in Y, Th and U towards the more evolved facies. When compared to zircons
of no tin-mineralized granitic rocks suggest an effective participation of magmatic
differentiation or hydrothermal alteration of their host rocks by F-rich fluids in their
genesis. The geochemical signature found in zircon crystals of tin-specialized
granites from different provinces of the Amazonian Craton shows that zircon
composition can be used as a prospective guide for such type of mineralization. This
work identified and characterized zircon crystals and accessory phases (mineral
inclusions) found in different facies of the Madeira Granite, Pitinga Province, using
backscattered electron (BSE) and cathodoluminescence images, and semiquantitative
chemical analysis using a scanning electron microscope (SEM) coupled
with an EDS (Energy Dispersive Spectrometry), and X-ray diffractometry (XRD). The
morphological characteristics, the amount and type of mineral inclusions, and the
chemical composition of zircon crystals belonging to the wallrock rocks differ
significantly from those characteristics found in zircon crystals from the mineralized
facies of the albite granite, indicating that although semi-quantitative, the used
methodology can be a useful tool for the preliminary assessment of the potential of
tin-granites.
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