Characteristics of the surface sediments surounding Ly Son island and related mineral potentials

Abstract

The marine area surrounding Ly Son island, of Quang Ngai province demonstrates steep and complex sea - floor morphology due to the presence of submarine coral reefs developed above the Ly Son paleo - volcano. The data of grain - size and mineral compositon analysis show that surface sediments of the Ly Son island are subdivided into 09 different sediment groups: muddy sandy gravel, sand, gravelly sand, gravel mixed sand and gravelly muddy sand, gravelly mud mixed sand, muddy sand, silty sand, gravelly mud, whose major composition is dominated by quartz (15.0÷71.0%), shelf fragments (27.0÷81.0%), minor lithic fragments and feldspar. This indicates that surface sediments can come from multi - origins in this studied area. The distribution of those sedimentary groups is relatively complex. The northern region mainly contains coarser grained sediments (i.e., sanddy gravel, sand, etc.), while the southern region hightly apears finer grained sediments (i.e., mud and silt). The coarser grained sediments such as muddy sandy gravel and gravelly sand, which are mainly coral fragment and often concentrated in the steep terrain around the emerged islands, while finer grained sediments more like sand, silty sand, etc. mostly deposited inside the submarine incised channels and slopes. The data from heavy mineral analysis show that the main valuable placer are ilmenite, zircon, etc. but their grades are very low and hence little economic prospect (ilmenite accounts for 23.57÷23.83 g/m3; zircon accounts for 0.33÷4.53 g/m3); Minerals used as construction materials are concentrated mainly in coarse - grained sedimentary fields (sand, gravelly sand and gravel mixed sand) with economic potential to serve construction needs on Ly Son island.