Prospecting for Impregnated Metasomatic Sulphur Deposits in Japan

Prospecting for New Deposits

Abstract

(1) The average size of the workable, impregnated, metasomatic sulphur deposits in Japan is 256m in diameter (321m×192m) and 29m thick.
(2) The ore deposits are generally found in irregular konides, and never in regular konides.
(3) The dip of the ore deposits depends upon the bedding of the country rock ; consequently, it, is slightly under 15°, which is nearly the same as the slope of the skirt of the konide.
(4) From the nature of volcanic structures, it can be expected that fumaroles, steam vents, ore deposits, volcanic bed-rock and hot-springs will be distributed in zones of decreasing altitude according to the order given here, however the relative altitudes of these zones will not vary greatly from each other.
(5) It follows from (4) that the ore deposits are to be found between the steam-vent and hotspring zones. Because of topography, it is clear that ground water is better developed in the hot spring zone than in the steam vent zone.
(6) It follows from (5) that one is most likely to find ore deposits in the zone of the break in slope between the breast and skirt of the konide.
(7) The dissection of a volcano begins at the top of the konide and ends on its skirt. Therefore, the location of the ore deposit is not liable to be affected easily by dissection because of the time lag involved and also because of the following probabilities.
(8) The interval between adjacent radial valleys of a volcano averages about 1km whereas the diameter of the ore deposits, as mentioned above, are on the order of about 256m, the ratio being roughly one to four. Therefore the probability of an ore deposit being dissected by a radial valley is rather small.
(9) Further, the ore deposits are considered generally to lie at depths of from 150m to 200m, whereas the depth of the radial valleys measures at most only 50m. Therefore the probability of an ore deposit cropping out is expected to be small.
(10) When the size of the sulphur deposits in Japan is considered, it is found that the size of the Matsuo deposit exceeds by far that of other deposits such as Abuta and Zao. Deposits still smaller than those of Abuta and Zao are abundant. These facts indicate the probable existence of hitherto undiscovered ore deposits, the size of which lie between those of Matsuo and Abuta-Zao.
(11) From (7), (8), (9) and (10), we can presume a high probability for future discovery of many more ore deposits in Japan, provided we prospect untiringly.
(12) In view of the aforementioned small probability that the ore deposit will crop out, the use of geophysical and geochemical prospecting methods are recommended.