Laya Roozbahani; Mohsen Arvin
Volume 1, Issue 2 , September 2010, , Pages 1-16
Abstract
The Upper Eocene sub-volcanic rhyolitic rocks of Nasir-Abad area, in south-west of Rayen, (placed in Kerman province -Iran) are under the pyroxene-andesite rocks of Lower Eocene volcano-sedimentary ...
Read More
The Upper Eocene sub-volcanic rhyolitic rocks of Nasir-Abad area, in south-west of Rayen, (placed in Kerman province -Iran) are under the pyroxene-andesite rocks of Lower Eocene volcano-sedimentary complex of Razak formation, which is a part of Uromieh-Dokhtar Volcanic Belt. One of the main characteristics of these sub-volcanic rhyolitic rocks, is their columnar joints structure, in which most parts are vertical and occasionally with a 50-degree to 70-degree tilting to the east. The general shape of the these joints, are often 5 to 6 sided volumes, but rarely 3, 4 and 7 sided volumes are also visible. These structures have been formed during the chilling process of the magma mass. The sub-volcanic rhyolitic rocks have microporphyry texture, but according to some thin sections, glomeroporphyry and felsophyric textures have been observed. It is worthnoting that, alkali feldspar, plagioclase, quartz, biotite and hornblende are the main mineral constituents. The pyroxene-andesitic rocks consist of porphyritic textures with plagioclase, amphibole and pyroxene as the main mineral constituents. Secondary minerals such as chlorite, calcite, sericite and epidote exist in both types of rocks. Investigation of the results of geochemical data, and tectonic discrimination diagram indicates that: the sub-volcanic rhyolitic rocks have characteristics of metaluminous, calk-alkaline, I-type granitic rocks and that the andesitic rocks derived from a rich mantle. Moreover, they were formed in a volcanic arc setting in an active continental margin environment.
