DETERMINATION OF MAGMA COMPOSITION USING COMPOSITIONAL VARIATIONS OF OLIVINE IN SERPENTINITES, KEMPERSAI MASSIF, KAZAKHSTAN

Abstract

Serpentinites are widely recognized as important hosts for understanding mantle processes and magmatic evolution. This study focuses on the compositional variations of olivine in serpentinites collected from the Aktobe region within the Kempirsai Massif in the Southern Ural Mountains of Kazakhstan. The objective of this research is to investigate the applicability of olivine chemistry as a tool for interpreting the composition of the parent magma and the associated tectonic setting. Samples were collected from the Kempersai Massif, an area known for its complex geological history and the presence of serpentinites. Three samples, referred to as AK-3, AK-4, and AK-6, were taken from thin sections obtained from serpentinite rock formations in the research area. These particular samples were selected for their high concentration of olivine. The samples were then examined using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to analyze the major cation elements present in the olivine crystals. Notably, efforts were made to select large olivine crystals of approximately 200 microns to ensure their magmatic origin and minimize the influence of secondary processes. Initial results show some small differences in the composition of olivine in the samples that were studied. The differences seen in the chemistry of olivine give clues about the range of magma sources and processes at work in the Kempersai Massif. These variations could indicate the process by which magma is formed, such as different levels of partial melting. It is noteworthy that the high Forsterite (Fo) content (≥ .88-.92) shows that the olivine grains in these samples are magmatic and preserve the original magmatic composition. Understanding the petrogenetic processes preserved in olivine compositions is crucial for reconstructing the magmatic evolution of the Kempirsai Massif and the Southern Ural Mountains region. By decrypting the origins and changes of magmas, this study enhances our comprehension of the geological dynamics in the area and its impact on mineral exploration and resource assessment in comparable geological settings.