Petrology, Geochemistry and Geodynamic Setting of Gabbroic Subvolcanics in the West of Shafarud, Talesh Mountains

Keshavarz Hedayati, M; Emami, M.H; Karimi Bavand Pour, A.R; Bahar Firouzi, Kh

doi:10.22071/gsj.2015.42425

Petrology, Geochemistry and Geodynamic Setting of Gabbroic Subvolcanics in the West of Shafarud, Talesh Mountains

Document Type : Original Research Paper

Authors

M Keshavarz Hedayati ¹

M.H Emami ²

A.R Karimi Bavand Pour ³

Kh Bahar Firouzi ⁴

¹ M.Sc. Student, Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran

² Associate Professor, Islamic Azad University, Islamshahr Branch; Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran

³ M.Sc., Geological Survey of Iran, Tehran, Iran

⁴ Ph.D., Geological Survey of Iran, Tehran, Iran

10.22071/gsj.2015.42425

Abstract

The microgabbroic sills and dikes have injected into the late Cretaceous limestones along Shafarud. Based on the textural and mineralogical features, they are divided into four groups: micro olivine gabbro, microgabbro, microgabbro-diorite, and diabase. The main minerals in these rocks are olivine, clinopyroxene, amphibole, and plagioclase. The spider diagrams show that the primary mafic magma is probably originated from the asthenosphere, but due to contamination with upper continental crust during eruption has been modified to calc-alkaline. As a result, depletion of Nb and enrichment in Pb, Rb, Cs, Th, and U is observed. Discrimination diagrams show that the primary alkaline microgabbros influenced by AFC process and modified to calc-alkaline rocks. The presences of pyroclastic enclaves in diabasic rocks indicate that the diabasic rocks are younger than the pyroclastic rocks.

Keywords

Microgabbroic sills and dikes

Shafarud

Asthenosphere