Protrozoic & Palaeozoic magmatism in Bafq Sheet & ItsRelation With Iron Ore Genesis

Category Petrology
Group GSI.IR
Location 21th symposium on geosciences
Holding Date 21 May 2008

      The area is located in the range coordinate of 55? , 00? ? 55? , 30? east longitude and 31? , 30? ? 32? , 00? north latitude in Yazd province. The oldest rock unit consists of metamorphic rocks of andalusite schist, staurolite garnet schist, amphibolite schist, gneiss, meta sandstone and crystallized limestone that outcrops at the northeast of Bafq sheet. This unit is named Boneh Shuru complex. Protolith of these rocks are graywacke, tuff, lava, sandstone and pellite (Razavi, M. H., 1993). Boneh Shuru metamorphic rocks are cut by intrusive rocks of alkali granite, mylonitic quartz ? feldespat rocks and diabasic dikes. Tectonized rhyolite, andesitic lava flows and acidic tuff of Risu series lie on Boneh Shuru metamorphic complex. Monzo-diorite, syenite
   intrusive rocks cut volcanic rocks of Risu series
   Pink alkali-granite outcrops at the northeast of Bafq area and cut by dark green diabase, micro-gabbro?micro diorite. Construction of metamorphic and granitic rocks are occurred in the conditions of compression pressures related to the Pan African phases (pre-Lower Cambrian), after it at Lower Ordovician basic magmatism occurred in tensional pressure conditions (Hooshmandzadeh, 1988).
   Generation of iron masses are accompaniment with syenitization of intrusive rocks, alkalic metasomatism and tremolite ? actinolitization of mafic minerals like pyroxene. In iron mines we can see tremolite ? actinolite, albite, hematite, quartz, serisite, argill, chlorite that are products of alteration. In mantle diapirs sodic pyroxenes of jadeite and acmite concentrate at 15 to 20 kilometers depth and then divide into immisible rhyolitic magma and iron solutions. In that process release free oxygen that makes magma thiner and lighter and helps that for ascension (Forster, 1981). In the Bafq area magnetite and hematite minerals with quartz?feldespatic magma are seen as two immiscible phases.

tags: YAZD