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Geology and mineralogy of the Linares area, a new gold mineralization in the Navelgas Gold Belt, western Asturias, Spain.
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
A. Martin-Izard, S. Combrink, L. Rodriguez-Terente, J. García-Nieto, H. Barrio-Alonso, L. Rodriguez-Pevida
In the studied area (Fig. 1) four small intrusions of biotite granites are located. The biggest one (1000 by 700 m) is porphyritic in character and outcrops to the south of Arganzua village. The granite is dated (Geochron lab) by the K/Ar method using primary fresh biotites from the drill cores, giving an age of 290±6 Ma. At the northern side of this granite outcrops a small equigranular granite. The age obtained by the K/Ar method using biotites from the drill cores is 276±6 Ma. The other two granite stocks are porphyritic in character as is the porphyritic granite from Arganzua. Both granites are monzogranites, but the porphyritic granite is close to the granodiorite field and the equigranular to the syenogranite field. Both are slightly peraluminous with high potassium content.
A unifying model for tin mineralisation in granites–pegmatites–greisens and veins: an African perspective
Published in Applied Earth Science, 2019
Tin-bearing magmas generally have monzo- to syenogranite compositions. Primary cassiterite-hosting deposits require a combination of factors: (i) the generation of magma, (ii) ascent of the magma through structurally-controlled passageways, (iii) crystallisation of the magma with or without fluid separation, (iv) generation of a hydrothermal fluid phase, and (v) escape of a hydrothermal fluid. The style of tin deposits can be grouped into different categories based on whether, and when, a fluid phase separated from the magma: Zoned and unzoned pegmatites generated as small melt fractions without a parent granite at depth. Magmatic cassiterite may have crystallised at the pegmatitic stage or/and from later hydrothermal alteration of the pegmatite, including the formation of a greisen (Fuchsloch 2018).Disseminated mineralisation in granite cupolas where fluid was retained.Irregular greisenised or tourmalinised zones of a granite cupola where hydrothermal fluids separated from the magma before the ductile–brittle transition.Pipes, stockworks, sheeted veins and greisens within a granite cupola after the ductile–brittle transition.Exogranitic greisens and sheeted veins within the country rock with associated alteration of the country rock and localised occurrence of skarns.Later endo- or exogranitic quartz-rich cassiterite-wolframite bearing veins representing the last stage in fluid evolution.Metamorphic re-distribution of cassiterite into zones of altered host rock.Alluvial and eluvial deposits derived from any of the above cassiterite-bearing deposits.