REE Characteristics and REE Mixing Modeling of the Proterozoic Quartzites and Sandstones

H Wani

doi:10.4236/ijg.2017.81002

Abstract

Rare earth elements (REE) in sedimentary rocks are most suitable for source rock characterization. Rare earth element data of the sandstones of the unmetamorphosed Meso-Neoproterozoic Chhattisgarh and Indravati basins and the metamorphosed Paleoproterozoic Sakoli and Saucer basins of the Bastar craton have been studied for source rock characterization. The quartzites have higher ∑R EE mean value (145 ppm) compared to the sandstones (34 ppm). The REE patterns of all the three formations of the Chandarpur Group of the Chhattisgarh basin and the Tiratgarh Formation of the Indravati basin are uniform and there are no systematic differences in REE patterns among different formations of the Chandarpur Group and the Tiratgarh Formation. The REE patterns of the quartzites are similar to the REE patterns of the sandstones. Chondrite-normalized REE patterns with LREE enrichment and a strong negative Eu anomaly of the sandstones and quartzites gives a broad hint about felsic source rocks. The source rocks are identified as Archean granite and gneiss of the Bastar craton. The REE mixing modeling of the sandstones and quartzites suggest that the exposed the Proterozoic upper crust of the Bastar craton during the sedimentation of the Paleoproterozoic Sakoli and saucerand the Meso-Neoproterozoic Chhattisgarh and Indravati basins of the Bastar craton was largely consisted of gneissic rocks (70%), with a little contribution (20%) from Late Archean (2.5 Ga) granites. The present study does not suggest any significant change in the upper crustal composition during Proterozoic in the Bastar craton.

Highlights

The Rare earth elements (REE) mixing modeling of the sandstones and quartzites suggest that the exposed the Proterozoic upper crust of the Bastar craton during the sedimentation of the Paleoproterozoic Sakoli and saucerand the Meso-Neoproterozoic Chhattisgarh and Indravati basins of the Bastar craton was largely consisted of gneissic rocks (70%), with a little contribution (20%) from Late Archean (2.5 Ga) granites
The REE data indicates source rocks for the Meso-Neoproterozoic sandstones, and the Paleoproterozoic quartzites were felsic in nature and the source rocks are identified to be granite and gneiss of the Bastar craton
The sandstones of the Chhattisgarh basin and the Indravati basin show REE similarities, indicate homogeneity in the source rock composition during the Meso-Neoproterozoic time and indicate that the sediments for the MesoNeoproterozoic Chhattisgarh and Indravati basins have been derived from similar sources i.e. granite and gneiss of the Bastar craton

Summary

Introduction

Several trace elements like Y, Th, Zr, Hf, Nb, Sc and rare earth elements (REE) are most suitable for discriminations of provenance and tectonic setting because of their relatively low mobility during sedimentary processes and their short residence times in seawater [2]. These elements probably are transferred quantitatively into clastic sediments during weathering and transportation, reflecting the signature of the parent materials and are expected to be more useful in discriminating tectonic environments and source rock compositions [1] [3] [4]. We have used the rare earth element (REE) data of the sandstones of the unmetamorphosed Meso-Neoproterozoic Chhattisgarh and Indravati basins and the metamorphosed Paleoproterozoic Sakoli and Saucer basins of the Bastar craton for source rock characterization and to know the Proterozoic crustal composition

Geological Setting

Sampling and Methodology

Results

Discussion

Conclusions

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