Vein-type Ore Deposits Research Articles

Antimony vein deposits of China

The Chinese antimony vein-type ore deposits account for 55% of the world's reserves of antimony. About 85% of China's antimony production comes from Human Province, largely from the giant Xikuangshan deposit (the world's largest Sb deposit). China's Sb deposits occur in four belts. Most deposits are located in the Provinces of Jiangxi, Hunan, Guangdong, Guizhou, Guangxi and east Yunnan within the circum-West Pacific Sb belt which, together with Australian and Japan etc., constitutes the world's most important area for Sb. The Sb vein-deposits of northwest Hubei and Shanxi Provinces extend into “Russian” Central Asia to form the Qinling-Central Asia Sb belt, the second-most important in China. The two other Sb belts account for only 0.2% each of China's Sb reserves: the deposits in west Yunnan belong to the Mediterranean Sb belt that extends west through Yugoslavia, Italy and Spain; while the deposits in North China belong to the Jilin-Daxinganling-Tianshan-Outer Baikal belt that extends into Siberia. The major Chinese Sb deposits can be divided into three groups: (1) pure stibnite deposits, which account for about 67% of reserves and are typified by the Xikuangshan deposit, Hunan; (2) SbAuW deposits, which account for 21% of reserves and include the Woxi, Hunan, and Gongguan, Shanxi, deposits and; (3) sulphantimonates-base metal deposits, which account for 12% of reserves are typified by the Dachang deposit, Guangxi. Chinese vein-type Sb deposits are classified and described in terms of their host-rock lithologies (seven classes) and age of their enclosing strata (Devonian host-rocks predominate). Structure appears to be the primary ore-control; six orecontrolling structural features have been recognised throughout China ( abstracted by the Editor).

Réflectance et composition chimique des bravoïtes du gîte sédimentaire de Chaudfontaine et du gîte filonien de La Rochette (Province de Liège, Belgique)

This paper deals with the study of the morphological, optical and chemical features of bravoites from a sedimentary ore deposit (Chaudfontaine) and a vein-type ore deposit (La Rochette). In both cases, the reflectance and the chemical composition have been compared. Besides a zoned structure, a spotted structure has been observed in the core of some crystals. Furthermore, the correlation between reflectance and Ni-content has been confirmed only for Co-poor bravoites.

On strontium isotopic ratio of barite from Kuroko-type ore deposits, Japan.

Strontium isotopic ratios (strontium-87/strontium-86) of five barite samples from five Kuroko-type and vein-type ore deposits in Northeastern Japan and Southwestern Hokkaido were measured mass-spectrometrically. The values obtained are quite uniform, being in the narrow range between 0.7040 and 0.7044±0.0004. These values are extraordinarily low in comparison with the recent data for a number of sulfate minerals from Fukazawa and Kosaka Kuroko-type ore deposits (Farrell et al., 1978). It is suggested that the strontium isotopic level of Kuroko ore-forming solution might have in some cases lowered down almost exactly to that of Tertiary volcanic rocks depending possibly on the degree of interaction between the ore-forming solution of normal sea water origin and the volcanic rocks (Farrell et al., 1978).

The influence of pre-existing planes of weakness in rocks on the localization of vein-type ore deposits

Localization of lead-zinc deposits in the mid-Wales ore field, United Kingdom, occurred where cross-cutting mineral veins were deflected by pre-existing sets of ac joints. Such deposits are frequently attributed to the infilling of open spaces formed by the intersection of premineralization fractures. This concept is not supported by the presence of analogous open spaces in unmineralized fracture systems. It is suggested that some ore shoots in the mid-Wales lodes were formed by the opening of ac fractures under the hydraulic pressure of the ore fluids during the mineralization process. Any planar anisotropy in a rock can affect the development of a hydraulically formed mineral vein, and the suggested mechanism probably operated during the formation of deposits in other ore fields.