Title: Mineralogical studies of Cretaceous phosphatic nodules of Nambakuruchi block of Tiruchirappalli District, Tamil Nadu, India

Authors: Ajhar Hussain; Kr. Farahim Khan; Firoz Ahmad

Addresses: Department of Geology, Aligarh Muslim University, Aligarh, 202002, India ' Department of Geology, Aligarh Muslim University, Aligarh, 202002, India ' Department of Statistics and Operations Research, Aligarh Muslim University, Aligarh, 202002, India

Abstract: The Cretaceous phosphatic nodules of study area are found in different sizes and shapes. Elliptical, cylindrical, globular, conical and irregular, with veins containing calcite, gypsum and celestite and minor amount of the montetrisaite are the common shapes. The thin section, X-ray diffraction and scanning electron microscope (SEM) studies show that the carbonate fluorapatite (CFA) is the main phosphate mineral of apatite family. Minerals like calcite, quartz, feldspar, kaolinite, chlorite, montimorlinite are the minor constituents. The crystal of the phosphate is brown to grey colour with bryozoan fragments. The fine phosphatic grains of nodules with silt size are embedded in fine matrix. Fragments of the fossils and others small carbonate particles show light to dark lamination. Coated grains, peloids, and fine detrital grains are found in these nodules. The shape of the peloids is rounded and having no well-defined structure which indicates fluctuating/or high energy environmental conditions. Micro cracks with microbial mat are also common with algal structure. Presence of organic matter, calcite, quartz and feldspar minerals is strongly supporting oxic to suboxic environmental conditions.

Keywords: phosphatic nodules; Cretaceous; Nambakuruchi; carbonate fluorapatite; CFA; mineralogy; India.

DOI: 10.1504/IJMME.2023.131608

International Journal of Mining and Mineral Engineering, 2023 Vol.14 No.1, pp.41 - 54

Received: 10 Apr 2022
Accepted: 08 Sep 2022
Published online: 20 Jun 2023 *