The tsavorite (gem quality green vanadium grossular) minerogenetic system in East Africa: a case of metamorphic partial
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CAJG 2018: TOPIC 10
The tsavorite (gem quality green vanadium grossular) minerogenetic system in East Africa: a case of metamorphic partial melting and lateral secretion Walter Leopold Pohl 1 Received: 24 May 2019 / Accepted: 27 August 2019 # Saudi Society for Geosciences 2019
Abstract When supercontinent Rodinia began to break up at ~ 800 Ma, wide rifts formed evolving into a passive margin of the Mozambique Ocean. At one stage, organic-rich pelites with gypsum/anhydrite (the later host rock of tsavorites) were interbedded with siliciclastics, carbonates, and bimodal volcanic rocks. Later, ocean closure, subduction, collision, and welding of various microcontinents and volcanic arcs formed the Mozambique Belt and at ~ 550 Ma, ended with the assembly of supercontinent Gondwana. In East Africa, deformation and metamorphism climaxed at 615–600 Ma. At peak metamorphic conditions, anatexis of siliciclastic metasediments produced abundant metamorphic mobilizates such as pegmatites and quartz veins. In the graphite schist hosting tsavorites, however, partial melting only produced small fractions of a supercritical hydrous liquid, the peculiar corrosive nature of which was due to the reduction of Ca-sulfate by reaction with organic C. Most of this melt/fluid phase remained within the host but migrated over short distances into structural traps of different origin; turbid green grossular crystallized from the melt and transparent tsavorite from residual fluids. Keywords Mozambique Belt . Metasediments . Anhydrite . Graphite . Anatexis . Minerogeny
Introduction Modern metallogenetic and minerogenetic research aims at understanding the whole source–transport–trap system. Source rocks are rarely accessible and identification mostly rests on geochemical models. Here, we describe the case of garnet gemstone districts in the Mozambique Belt of East Africa (Fritz et al. 2013) where partial melt secreted from high-grade metamorphic rocks. Remaining within the source lithology, it migrated short distances into low-pressure structural traps where gemstones formed. The aim of this paper is to establish the minerogenetic system for tsavorite (gem
This paper was selected from the 1st Conference of the Arabian Journal of Geosciences (CAJG), Tunisia 2018 Responsible Editor: François Roure * Walter Leopold Pohl [email protected] 1
Austrian Academy of Sciences, Dr. Ignaz Seipel-Platz 2, 1010 Vienna, Austria
quality green vanadium grossular) deposits to be applied in exploration and mining.
Methods We modify the template of the metallogenetic or mineral system analysis (MSA), which is a holistic genetic investigation identifying all factors and processes that contribute to the origin of a mineral deposit, similar to petroleum systems (Hagemann et al. 2016). In practice, mineral system analysis can be conceived as the modern high-technology application of metallogeny updated by current analytical technologies (Pohl 2019). By employing GIS and probability science in exploration, target models are based on the underlying mineraliza
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