Petrography, geochemistry, and provenance of the Chalki rocks in Kurdistan region, North Iraq
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ORIGINAL PAPER
Petrography, geochemistry, and provenance of the Chalki rocks in Kurdistan region, North Iraq Sarmad Asi Ali 1,2 & Muhamed Fakhri Omer 3 & Ahmed Mohammed Aqrawi 3
Received: 24 November 2015 / Accepted: 3 June 2016 # Saudi Society for Geosciences 2016
Abstract Outcrops of the Paleozoic Chalki volcanic rocks are restricted to part of the northern Thrust Zone of Iraq close to Iraqi-Turkish border. Petrographically, the volcanic rocks from the Chalki area are mainly layered, appearing fresh in the field and exhibiting some basaltic lava flows. Porphyritic, amygdaloidal, and microlite-porphyric are the main observed textures. Phenocrysts of primary phases (i.e., olivine, iron oxides) are in a groundmass of feldspars and clinopyroxene. Chalki Formation is intercalated with Pirispiki Formation which consists of thin to medium bedded, greenish gray marl, red mudstone, and veins of calcite. The Chalki rocks are mafic of theolitic basalt type. Geochemically, they have high chromium and nickel concentrations in most samples. Rare earth element (REE) patterns illustrate parallel to sub-parallel, moderately fractionated REE patterns. The low heavy REE (HREE) contents in the studied samples appear to be due to partial melting of metamorphosed oceanic crust leaving HREE-rich accessory minerals (i.e., garnet) as a residual phase in the source. No Eu anomalies were observed in the Chalki samples which may indicate a back-arc basin pattern. The non-subduction signature of the Chalki rocks is confirmed by the Nb/Yb versus Th/Yb diagram, which shows that
* Muhamed Fakhri Omer [email protected]
1
Department of Applied Geology, College of Science, Kirkuk University, Kirkuk, Iraq
2
GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW 2522, Australia
3
Department of Geology, College of Science, Salahaddin University, Erbil, Iraq
most of the studied rocks fall in the compositional field of non-arc-related rocks—well within the field of the midocean ridge basalt (MORB)-ocean island basalt (OIB) mantle array. Keywords Chalki formation . Petrographic . Geochemistry . Basaltic rocks . Provenance . Northern Iraq
Introduction The Zagros orogenic belt extends from eastern Turkey through NE Iraq and along SW Iran to Oman (Fig. 1). It marks the collision between the Arabian and Iranian plates in the northeast and the Arabian and Turkish plates in the north (Searle et al. 1980; Abbotts 1981; Hall 1982; Babaie et al. 2001; Omrani et al. 2008; Aswad et al. 2011; Ali 2012; Ali et al. 2012, 2013). Access to this part of Iraq during the past four decades has been limited due to ongoing war and landmine threats making some areas virtually inaccessible to study. However, some previous works (e.g., Bellen et al. 1959; Buday 1980; Buday and Jassim 1987) suggest that volcanic rocks exist in the northern Thrust Zone of Iraq close to Iraqi-Turkish border. The nature of this group and the structures along which it was thrusted or not is still poorly understood. Part of th
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