Distribution of some ore metals around the Mau Due stibnite deposits, northernmost Vietnam

Abstract

Soil and stream sediments were studied geochemically around the Mau Due ore deposits of the northernmost Vietnam. The ore deposits are fracture-filling type occurring in Devonian sediments composed mainly of impure calcareous sediments. The chemical elements brought up by the mineralizations are mainly S and Sb, and small amount of As and base metal. The analyzed surface samples were collected in the wet season (May to September) and the dry season (October to April).Sb contents of surface materials are sporadically high in the soil samples, and have smaller variation in the stream sediments than in the soil samples. Sb contents of the soil of the wet season, 932 ppm Sb in the average, are higher than the average of 342 ppm Sb of the dry season. The Sb contents are much higher in the stream sediments, averaged as 2,536 ppm in the wet season and 2,504 ppm in the dry season.Generally speaking, As contents of the soil are positively correlated with Sb contents, but the amounts are much lower than the Sb contents, averaged as 29 and 26 ppm in soil of the wet and dry seasons, respectively, but higher as 68 and 67 ppm in the stream sediments. These abundance data of Sb and As are best explained by both elements are present finest grained sulfides in the soil and river sediments. The Devonian host rocks may be originally high in the Sb contents, as compared with the Japanese eugeosynclinal sediments.

Antimony leaching from soils and mine waste from the Mau Due antimony mine, North-Vietnam

“…It is composed of sandstones, black shale and sericitic shale and has a thickness of about 300 m (Xuan, 2011). The Mau Due Sb deposit is a small fracture filling-type Sb deposit (Ishihara and Xuan, 2013). Three ore bodies extend discontinuously in the North East -South West direction.…”

“…These orebodies are mostly composed of quartz (20-70 %) and small amounts of calcite (CaCO3). The ore minerals are stibnite, and very small amounts of pyrite (FeS2), arsenopyrite (FeAsS), sphalerite ((Zn, Fe)S), and berthierite (FeSb2S4) (Ishihara and Xuan, 2013). The average Sb content in the ore ranges from 3.13 to 12.03% (Xuan, 2011).…”

“…The average Sb content in the ore ranges from 3.13 to 12.03% (Xuan, 2011). Besides the primary ore mineral stibnite, secondary Sb-containing minerals are found, which were formed by the weathering of stibnite (Sb2S3): valentinite and lewisite (CaSb2O5(OH)2) (Ishihara and Xuan, 2013). In 1993, exploitation of the ore body was initiated by open-pit mining.…”

“…A refinery was installed in 2002. Since 2002, the annual Sb production of the mine amounts to 100 tons (Ishihara and Xuan, 2013), which is a substantial part of the total Sb production in Vietnam, which reached approximately 576 tons in 2017 (Doan, 2020). The climate in this region is subtropical, with cool winters.…”

“…Again, this will not allow for mapping of the Sb contamination in the area, but gives a preliminary indication of Sb concentrations in soils close to the slag heap. The geochemistry of soil and stream sediments around the Mau Due stibnite deposit has already been investigated (Ishuara and Xuan, 2013), but not the soils nearby the Sb refinery.…”