solomon Ahmadi Bonakdar; SEYED MOHSEN TABATABAEI MANESH; Akramosadat Mirlohi
Abstract
The occurrence of tourmaline is observed in two areas in the north of Golpayegan. In the first area, on the west side of Ochestan farm, tourmaline occurs inside the crystallised mass ...
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The occurrence of tourmaline is observed in two areas in the north of Golpayegan. In the first area, on the west side of Ochestan farm, tourmaline occurs inside the crystallised mass as subhedral (Gt), at contact with amphibole schist as automorph (At), and at contact with micaschist as a spongy (Mt). On the second area, lies tourmaline in the north of Esfajard village inside marbles (Ct). Gt-type tourmalines of schorl composition have Fe# > 0.93 and are of a magmatic origin and are compatible with granitoids poor in Li. Both types of Mt-type and At-type tourmalines of dravite and schorl-dravite compositions, possess hydrothermal origin and are compatible with Ca-poor meta-psammite and metapelite rocks. Ct-type tourmalines are of dravite composition and with Fe# <0.6, are compatible with Ca-poor meta-psammites and metapelites and coexist with an Al-saturated phase. The presence of Ct-type tourmaline next to biotites of corrosion traces and the presence of secondary minerals in the rock, as well as the difference in thermometry, all demonstrate the formation of tourmaline at a lower temperature due to the reaction of boron-containing fluids with biotite. In the creation of these tourmalines, fluids from the progressive metamorphism of micaschists andpostmagmatic/ residual - hydrothermal fluids related with alkali syenite magma have played a role.
