A.R Shaker Ardakani; S Dargahi; H Amirpour
Abstract
The Ghaleh-Ganj dioritic- quartzdioritic massifs, Post early Eocene in age, located on the west side of the Makran Accretionary Prism and the Jazmurian Depression and the east side of the Jiroft fault, are part of the intrusives in the Ganj Complex, which itself is a part of the Jazmurian Ophiolitic ...
Read More
The Ghaleh-Ganj dioritic- quartzdioritic massifs, Post early Eocene in age, located on the west side of the Makran Accretionary Prism and the Jazmurian Depression and the east side of the Jiroft fault, are part of the intrusives in the Ganj Complex, which itself is a part of the Jazmurian Ophiolitic Belt or the Inner Makran. The diorite- quartzdiorites are intruded into the Lower- Middle Eocene Bidak sedimentary units, which show spheroidal weathering and onion- skin erosion. The presence of feldspar, biotite and secondary minerals (such as clay minerals, secondary biotite and Fe oxides) in the study massifs played an important role in the occurrence of these features. Mineralogically the intrusives consist of plagioclase, clinopyroxene, amphibole, Biotite and opaques. Based on mineral chemistry studies, the plagioclases, oligoclase to labradorite in composition, show evidences of disequilibrium textures (e.g. sieve texture and oscillatory zoning). The clinopyroxenes are augite in composition and belonging to a tholeiitic magmatic series. Referring to linear relation between Ti and AlIV in clinopyroxenes, they seem to be formed in a pressure less than 5 kbs at a depth of less than 15 kilometers. Amphiboles are magnesiohornblende with tendency to actinolite in composition. Based on Zr/TiO2 versus Nb/Y and SiO2 versus Nb/Y diagrams, the intrusives plot in the fields of diorite- quartzdiorite and sub-alkaline, respectively. Their low Nb/Y ratio (0.14-0.16) also point out to their sub-alkaline (tholeiitic) nature. The intrusives are metaluminous and I-type, which referring to HFS and REE element contents, they belong to one group. The absence of a distinct Eu anomaly suggests the insignificance of plagioclase fractionation or oxidation state of the magma. The trace element discrimination diagrams together with chondrite-normalized rare earth element patterns show that the Ghaleh Ganj diorite- quartzdiorites formed in the Maturity Stage of a supra-subduction zone.
