Resource Evaluation and Some Genetic Aspects of Indium in the Japanese Ore Deposits

Abstract

There have been two primary sources for industrial indium; one from massive sulfides, while the other is dissemination-veins and skarns, related to felsic igneous rocks. The latter group of the In-bearing deposits is abundant in the Japanese Islands. Indium occurs as In-minerals such as sakuraiite, roquesite, laforetite and many unidentified minerals, but the majority is contained as an impurity in sphalerite, and tin and copper sulfides. Average grades of the ores from which indium has been extracted vary from a few ppm (e.g., Kosaka mine) to more than 300 ppm (Toyoha mine). The amount of indium in all the major basemetal deposits is estimated by analyzing representative samples. The main indium deposits are subvolcanic and tin-polymetallic vein types. The largest one is Toyoha mine (4,700 tons In) and the Ashio mine (ca. 1,200 tons In) was found to be the second largest. Many small occurrences, were recognized in the Miocene magnetite-series belt, besides the classic occurrences in the ilmenite-series granitic terrains of SW Japan, including the Ikuno and Akenobe tin(-tungsten) polymetallic veins, located in the northern margin of the late Cretaceous Sanyo ilmenite-series province. Magnetite-series magmas with deep source are necessary to concentrate sulfur in the magma chamber but sedimentary source rocks and their reducing agents are needed to collect and to precipitate indium. The Japanese islands are essentially accretionary terrains intruded by various deep oxidized magmas; thus forming magnetite/ilmenite-series paired belts, which are sometimes mixed. This unique geologic setting may be the most fundamental reason why indium is rich in vein-type deposits of the Japanese Island arcs.

Mineralogical Distribution of Germanium, Gallium and Indium at the Mt Carlton High-Sulfidation Epithermal Deposit, NE Australia, and Comparison with Similar Deposits Worldwide

“…Indium also has a slight tendency to be enriched in reduced, carbonaceous sedimentary rocks [124]. In the Japanese island arc, assimilation of basement pelitic rocks is believed to have played an important role in supplying In and reducing agents to the oxidized magmas that formed Toyoha and other In-Sn-bearing polymetallic vein deposits [11,16,121]. The HS deposits from which samples showed high enrichment in critical elements in this study (Mt Carlton, La Mejicana, Chelopech, Cerro Quema) are all hosted in stratigraphic sequences that locally contain carbonaceous sedimentary rocks ( Table 2, and references therein; [30]).…”

“…Due to their chalcophile properties, enrichment of these elements has been linked to sulfur-rich and oxidized magmatism [1, 9,11,16,121], typical of a porphyry-epithermal environment [23,122]. Additionally, Ge, Ga and In may be mobilized into magmas and hydrothermal fluids from sedimentary country rocks, in particular those rich in organic matter.…”

“…The most prominent example is the world-class Toyoha IS deposit in Japan. Toyoha was the world's largest In producer in the 1990s-early 2000s, containing 33,700 kt of ore with an average In grade of 138 ppm [11]. Similar to Mt Carlton, the main carriers of In at Toyoha are In-bearing sphalerite (up to 7 wt % In, 3.6 wt % Cu and 273 ppm Ga; [15,69]) and the "Zn-In mineral" [43].…”

Indium Mineralization in a Sn-Poor Skarn Deposit: A Case Study of the Qibaoshan Deposit, South China

“…Indium is hosted by many deposit types [1], and industrial In resources are generally associated with massive sulfide, granite-related vein, skarn, and disseminated deposits [2,4]. Although In occurs mainly in an isomorphic form in sphalerite, important resources are hosted in Sn-rich deposits.…”

“…With indium (In) being widely used in high-technology applications, it is important for geologists to understand the development of In deposits [1][2][3]. Indium is hosted by many deposit types [1], and industrial In resources are generally associated with massive sulfide, granite-related vein, skarn, and disseminated deposits [2,4].…”