PETROGRAPHY AND GEOCHEMISTRY OF SHAYKHAB SUBVOLCANIC ROCKS, CENTRAL ALBORZ ZONE, NORTHERN IRAN

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 1, 207-212 pp

ABSTRACT

The studied area is situated about 70 Km in west of Damghan, and from the structural
point of view, the area is part of south of central Alborz zone. Granitoid bodies intruded
into late Eocene volcanic and volcanoclastic, mainly composed of monzonite and
granite composition. Mineralogically, these rocks contain quartz, plagioclase, alkalifeldspare,
amphibole, clinopyroxene, biotite, zircon, apatite, and opaque minerals.
Textures of rocks are microgranular and field and textural evidences show that the
plutones are hypabyssal. In variation geochemical diagrams show two distinct fields and
is categorized as monzonite (metalminous) and granite (peraluminous). Geochemical
studies indicate that the nature of magma from these rocks located in calc-alkaline field
and belongs to I-type granitoids of continental volcanic arcs. Iron mineralization with
mainly composition of hematite occurred at the contact of masses and host pyroclastic
and limestones rocks, along faults and fractures zones.

Keywords: Geochemistry, Granitoid, Shaykhab, North Iran