Spatial distribution, geochemistry and provenance of heavy minerals in Miri beach sediments, NW Borneo, Malaysia

Abstract

In this study, the spatial distribution of heavy minerals (HMs) in Miri beach sediments was assessed to quantify the abundance and determine the provenance. Surface sediment samples were collected in Miri beaches during low tide with respect to longitudinal, lateral and depth samplings. The collected samples were processed for grain size analysis by using sieving method. Then the HMs separation at different grain size fractions was carried out by using gravity and magnetic separation methods. Polarising Microscope was used to identify various HMs present in the sediment samples. In addition, selected sediment samples were analysed by using X-ray Fluorescence (XRF) to determine the elemental composition and major oxides for the geochemistry and provenance. From the results, HMs found in Miri beach sediments were zircon, magnetite, tourmaline, and rutile. Magnetite was abundant in 600–250 μm size fraction, zircon in 125–63 μm size fraction, tourmaline in 125–63 μm size fraction, and rutile in 250–125 μm size fraction. Longitudinally, magnetite was found to have higher abundance towards the southern part of the coastline. However, the abundance of rutile and tourmaline was found in the northern part of the coastline. Zircon was more abundant in the middle and southern parts of the coastline. Laterally, the concentration of HMs was higher towards the landward side. In terms of depth, the distribution of HMs varies and abundant in the surface sample. Geochemically, the beach sediments were found to be highly weathered in the north beaches (CIA = 78.9), moderately weathered in the middle (CIA = 63.8 to 66.5) and poorly weathered in the southern beaches (CIA = 40.4–49.6). The high content of quartz in the sediments are derived from the quartzose sedimentary origin, which undergone recycling process. Environmental indices such as contamination factor (CF), geoaccumulation index (Igeo), and enrichment factor (EF) indicate that the Miri beach sediments were highly concentrated with Cr, Ni, and Ta.