Petrochemistry of a Late Precambrian garnetiferous granite, pegmatite and aplite, southern Israel

Abstract

Garnet is a widespread minor accessory mineral in the Late Proterozoic Elat-Quarry granite of southern Israel and is more abundant in the associated pegmatite and aplite. All garnets are dominated by almandine and spessartine end-members. Granite-hosted garnets are zoned with relative enrichment of Mn in the core and Fe in the rim. The chemistry of the garnet in the pegmatite and aplite are comparable to the rim compositions of garnets in the granite, but with a slight Fe-depletion at the rims. Geochemical parameters for the granite indicate fractional crystallization largely of an S-type source magma to a peraluminous composition.In the highly evolved granite magma, Fe is relatively diminished, and only small amounts of biotite can crystallize. Manganese becomes a compatible element forming Mn-rich garnet (cores), and reducing the Mn content in the magma, subsequently leading to Fe-enriched rims. The greater abundance of garnet in the pegmatite and aplite (and its larger crystal-size in the former) relate to the enhanced presence of a hydrous fluid within the magma. The tendency for garnet crystals to concentrate in bands is much more developed in the pegmatite than in the granite, and is associated with the effects of hydrofracturing (fracture-filling), and the crystallization of coarse-grained alkaline feldspars.

Radon daily signals in the Elat Granite, southern Arava, Israel

“…A prominent joint system cuts the body, striking approximately N45E. Elat Granite contains 1–3.5 ppm uranium [ Bogoch et al , 1997] and exhibits a radon level of 7.8 ± 4.3 kBq/m 3 at a depth of 0.5 m [ Shirav and Vulkan , 1997].…”

Occurrence of primary almandine-spessartine-rich garnet and zinnwaldite phenocrysts in a Neogene rhyolite on the island of Chios, Aegean Sea, Greece

“…According to Green (1977), spessartine-rich garnets in rocks of granitoid composition show evidence of formation at low P-T. In granites (Bogoch et al, 1997), the almandine-spessartine magmatic garnets are commonly zoned either with increasing Fe relative to Mn from core to rime or vice versa, depending on the nature of the granitic magma and the crystallization conditions. The composition of the almandine-spessartine garnets in pegmatites and aplites is more stable not showing any significant zoning.…”

“…It is suggested that this is associated with a rather specific tectonic setting in the broad eastern Aegean area, including Kos-Samos-Patmos-Chios and Bodrum, in a zone extending broadly in a N S orientation, that is transverse to the modern volcanic arc. Manganese-rich garnets crystallize from magmas enriched in volatile constituents (Baldwin and von Knorring, 1983;Bogoch et al, 1997). According to Green (1977), spessartine-rich garnets in rocks of granitoid composition show evidence of formation at low P-T.…”

The Pan-African high-K calc-alkaline peraluminous Elat granite from southern Israel: geology, geochemistry and petrogenesis

“…The magmatic origin of garnet in pegmatites and granites from the Wadi Shelomo pluton was justified by Bogoch et al (1997). Table 3 Microprobe analyses of muscovite from the EG and SGG (wt.%) The distinctions in chemical compositions of the minerals from magmatic and metamorphic rocks are significant.…”