Paper Information

Journal:   GEOSCIENCES   SUMMER 2017 , Volume 26 , Number 104 #H0055; Page(s) 149 To 162.
 
Paper: 

PETROLOGICAL AND GEOCHEMICAL NATURE OF MESOCRATIC AND MELANOCRATIC DYKES IN LAKHSHAK GRANODIORITE, NORTHWEST OF ZAHEDAN

 
 
Author(s):  SARHADDI N.*, AHMADI A., FIROOZKOOHI Z., JAMI M.
 
* DEPARTMENT OF GEOLOGY, FACULTY OF SCIENCES, UNIVERSITY OF SISTAN AND BALUCHESTAN, ZAHEDAN, IRAN
 
Abstract: 

The Lakhshak granodiorite body with Oligo-Miocene age crops out in flysch sediments of northwest of Zahedan. This body has been intruded by dykes with variable color indices ranging from mesocratic to melanocratic, and NE-SW trend. Based on field observations, melanocratic dykes have cut mesocratic dykes in some parts.This indicates that mesocratic dykes are younger than the melanocratic types. Different thickness (2 to 12m) of dykes shows the effect of tectonic activities and magama injection into structural joints, and the formation of dykes during tectonic activity. In terms of lithology, the Lakhshak body is composed of granodiorite, dacitic mesocratic dykes and melanocratic dykes of microdioritic and andesitic types. The granodiorite body and the two types of dykes are of I type nature, and are calc-alkaline, high-K calc-alkaline and metaluminous. Based on the geochemical characteristics, dykes and granodiorite show enrichment in LILE, LREE such as Ba, Cs, Rb, Eu and Pb, and depletion in HFSE, HREE such as Nb, Ti and Ta, which are related to index characteristics of the volcanic arc setting of an active continental margin. Pb positive anomaly may demonstrate continental crust assimilation by magma associated with mantle metasomatism. Based on field observation and petrogenesis, the Lakhshak granodiorite and mesocratic-melanocratic dykes originated from magmatic activity of subducted oceanic crust (Sistan plate) beneath the continental plate (Afghan block). The parental magma of the Lakhshak granitoid was originated from melts resulted from amphibolite melting, and dykes are the late derivative of magma recrystallization granodiorite.

 
Keyword(s): GRANODIORITE, DYKE, MESOCRATIC, MELANOCRATIC, PETROGENESIS, SUBDUCTION
 
References: 
  • ندارد
 
  Persian Abstract Yearly Visit 23
 
Latest on Blog
Enter SID Blog