GEOCHEMICAL APPLICATION IN UNRAVELING PALEOWEATHERING, PROVENANCE AND ENVIRONMENTAL SETTING OF THE SHALE FROM CHIA GARA FORMATION, KURDISTAN REGION, IRAQ

Rezhin K Mustafa

doi:10.46717/igj.53.1a.r7.2020.01.28

Abstract

The geochemical characteristics of the shale of the Chia Gara Formation (Middle Tithonian-Berriasian) from the Imbricated Zone (Barsarin section) and High Folded Zone (Banik section) Kurdistan Region, Iraq, was carried out to constrain their paleoweathering, provenance, and depositional environment. There are no clear differences in the major and trace elements of the Chia Gara Formation between the two studied sections. The chemical index of alteration (CIA) is significantly higher in the Barsarin than the Banik shales, suggesting more intense weathering of the Barsarin than the Banik shales. The samples of the Banik and some of Barsarin are clustered near the A-K line in A-CN-K plot suggests intense chemical weathering (high CIA) without any clear-cut evidence of K-metasomatism. The other samples of Barsarin have a weathering trend parallel to the A-CN line, indicating relatively steady state weathering conditions. The geochemical parameters of the shale (Al2O3/TiO2, Th/Sc, La/Th, La/Sc, La/Co, Th/Co, Cr/Th, (La/Lu)cn and Eu/Eu*cn), and the diagrams (Th/Sc-Zr/Sc and La/Th-Hf) indicate that they were derived from felsic (from the Rutba Uplift and/or Mosul High) and intermediate (from volcanic material during the spreading of Southern Neo-Tethys Ocean) components. The chondrite-normalized REE patterns are similar to those of Post Archean Australian Shale (PAAS), with the light rare earth element (REE) enrichment, a negative Eu anomaly, and almost flat heavy REE pattern. The geochemical parameters such as authigenic uranium, U/Th, V/Cr, Ni/Co, and V/Sc ratios, and Al2O3-V and Al2O3-P2O5 diagrams indicate that these shales were deposited under deep marine suboxic to anoxic environment and shale of Banik section was deposited slightly under deeper environment than shale of Barsarin section.

Highlights

The geochemistry of clastic sedimentary rocks is used as an effective tool in the study of source area composition (Cullers, 2000, 2002; Osae et al, 2006; Armstrong-Altrin, 2009; Saha et al, 2010), intensity of chemical weathering in the source region (Selvaraj and Chen, 2006; Roy et al, 2008; Gallala et al, 2009; Gupta et al, 2012; Raza et al, 2012), paleoclimatic conditions (Nesbitt and Young, 1982; Bhatia, 1983; Taylor and McLennan, 1985; Absar et al, 2009; Raza et al, 2010), provenance (Cullers, 2000, 2002; Armstrong-Altrin, 2009; Bakkiaraj et al, 2010) and tectonic setting of the sedimentary basins (Cullers, 2000; Armstrong-Altrin and Verma, 2005; Joo et al, 2005; Sabaou et al, 2009; Fatima and Khan, 2012)
Determination of the provenance utilizing the elemental geochemistry in identifying source rocks for sedimentary rocks is based on the relative immobility of certain elements like La and Th that have high value in felsic rocks relative to basic rocks and Co, Cr, Sc and Ni have high values in basic rocks relative to felsic rocks within surficial environments in order that the elemental concentration or ratio reflects the composition of source rock much better than weathering and transportation
The Chia Gara Formation is composed of organic matter-rich limestone and shale, it considered as an important petroleum source rocks (Odisho and Othman,1992; Al-Beyati,1998; Al-Ameri and Al-Obaidi, 2004)

Summary

Introduction

The geochemistry of clastic sedimentary rocks is used as an effective tool in the study of source area composition (Cullers, 2000, 2002; Osae et al, 2006; Armstrong-Altrin, 2009; Saha et al, 2010), intensity of chemical weathering in the source region (Selvaraj and Chen, 2006; Roy et al, 2008; Gallala et al, 2009; Gupta et al, 2012; Raza et al, 2012), paleoclimatic conditions (Nesbitt and Young, 1982; Bhatia, 1983; Taylor and McLennan, 1985; Absar et al, 2009; Raza et al, 2010), provenance (Cullers, 2000, 2002; Armstrong-Altrin, 2009; Bakkiaraj et al, 2010) and tectonic setting of the sedimentary basins (Cullers, 2000; Armstrong-Altrin and Verma, 2005; Joo et al, 2005; Sabaou et al, 2009; Fatima and Khan, 2012). Determination of the provenance utilizing the elemental geochemistry in identifying source rocks for sedimentary rocks is based on the relative immobility of certain elements like La and Th that have high value in felsic rocks relative to basic rocks and Co, Cr, Sc and Ni have high values in basic rocks relative to felsic rocks within surficial environments in order that the elemental concentration or ratio reflects the composition of source rock much better than weathering and transportation. The main purpose of this study is to determine the provenance, chemical weathering and the redox conditions for the shale of the Chia Gara Formation

Objectives

Results

Discussion

Conclusion