A great number of pumices occurs in the submarine acidic pyroclastic rocks of Sainokami and Shakanai formations which develop around the Kuroko deposits of the Shakanai Mine. These pumices are generally found showing an elongated outline, as clearly as that of welded tuff, which is approximately parallel to the bedding plane. The writers measured the ratio of the maximum length to the minimum one of the pumices. We call the ratio "degree of flattening" in this report. The flattening seems to be due to one or more of the following reasons; compaction during diagenesis, Kuroko mineralizations, post-mineralization activities, environment of the pyroclastic rocks piled up, and nature of the pumice.
The maximum/minimum ratios in the barren zone, which is several hundred meters from the ore body, varies from 2 at the upper formation, to 32 at the lower formation. We consider this is simply caused by the load pressure of rocks deposited after the individual formation. The ratio around the mineralized zone is higher than that in the barren zone, even within the same horizon. We consider this to be due to the argillization related to the mineralization and post-mineralization activities.
In some places degree of the flattening in the lower formation is smaller than that of the upper formation. In such cases, the pumice of the lower formation occurs in the pyroclastic rocks intercalated with mudstone, or in a transitional phase of the pyroclastic rocks to rhyolite. Amount of pumice and degree of the vesiculation decrease toward the xhyolite side. Therefore, we consider this phenomenon depends on place where the pyroclastic rocks piled up, and degree of the vesiculation of the pumice. But pressure of the sea water.in which sedimentation of the pumice occurred and composition of the pumice are needed to be considered in further studies.
As compared with pumices of welded tuff, the elongated pumices of the submarine pyroclastic rocks are different in retaining vesicles and having higher degree of the fattening that generally increases downwards.

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This area studied consists of two geologic elements, pre-Neogene geosynclinal sedimentary rocks, and Neogene sedimentary and igneous rocks. The older formations showing monoclinic zonal arrangement, parallel to the major Paleozoic structure in Southwest Japan, and contain many Kieslager ore deposits of small size, of which main mineral is fine-grained pyrite. In Neogene, granitic intrusion (Omine granite), sedimentation in small basins (Miyai formation) and acidic extrusive activities (Kumano acidic extrusive rocks) occured successively. At the last stage of the Neogene tectonics, numerous faults and fissures were formed allover the tectonic area. This was followed by the Kinan copper mineralization.
Ore deposits of the Kinan-type, the most important one in the area, are classified into two local types on the basis of mineral assemblages and texture of vein-forming minerals. Kitayama-type deposits, which are characterized by fine-grained pyrrhotite, represent a deeper phase of the Kinan mineralization, while the other, Kishu-type deposits, represent shallow one. Chalcopyrite-pyrite veins of the famous Kishu and Myoho mines belong to the latter group of the ore deposits.

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The writers studied fluid inclusions in minerals from the Ohtani and Kaneuchi mines, which belong to the hypothermal or pegmatitic tungsten vein-type deposit, by means of the heating stage- and cooling stage-microscope and decrepitation methods.
(1) By the heating-stage microscope, the filling temperatures of inclusions are measured as follows (Figs. 3, 4);
Ohtani mine: quartz 375°-225°C, scheelite 337°-262°C, cassiterite 345°-297°C.The maximum filling temperature of quartz is 375°C, which is exceptional as shown in Fig. 3. Most of the filling temperature of quartz are below 300°C.
Kaneuchi mine : quartz 308°-231°C, scheelite 318°-276°C, wolframite 337°-286°C.The filling temperatures of the inclusions in scheelite, cassiterite and wolframite are somewhat higher than those in quartz. This would be due to the fact that the quartz crystals studied were deposited at the later stage of mineralization. The earlier stage quartz is white and milky in colour, so it is difficult to observe the inclusions of the earlier stage quartz under the microscope.
(2) By the cooling-stage microscope, the NaCl equivalent concentrations in inclusions are determined as follows (Figs. 5, 6);
Ohtani mine : quartz 7.4-4.0 wt. %, scheelite 8.2-6.1 wt. %, cassiterite 8.7-6.1 wt. %.
Kaneuchi mine : quartz 8.2-3.7wt. %, scheelite 8.6-6.4wt. %, wolframite 8.4-8.1 wt. %. The NaCl equivalent concentrations in scheelite, cassiterite and wolframite are higher than those of quartz. This would be due to the same reason as of the filling temperatures stated above.
(3) The filling temperature increases with the increase of the NaCl equivalent concentration (Figs. 7, 8). This would be due to the dilution of the ascending ore-forming fluid by the underground water.
(4) In the Ohtani mine, the fluid inclusions in quartz from greisen and granodiorite adjacent to the greisen envelope are nearly the same as those in the vein materials. The ore-forming fluid would be concentrated in the granitic magma existed in the deeper part underneath the present country rock, i.e., granodiorite.
(5) The decrepitation temperatures of quartz samples in both deposits are as follows :
Ohtani mine 382°-280°C, Kaneuchi mine 334°-255°C.
It is inferred that the formation temperatures of the Ohtani mine are higher than those of the Kaneuchi mine.
(6) It is generally said that the decrepitation temperatures are higher than the filling temperatures because of the overshoot effect. The samples of quartz which were used in the decrepitation method of the present study belong to the early stage of mineralization than those in the heating-stage microscope method. Therefore, it is probable that the temperature differences between the heating-stage microscope method and the decrepitation method are due to both overshoot effect and difference of the stage of quartz deposition. But, it is also probable that there exist other factors which make the difference between the filling temperatures and decrepitation temperatures.

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On the basis of available thermochemical and crystallochemical data for the systems PbS-PbSO₄ and BaS-BaSO₄, it is shown that the lead content of barite (and possibly also the barium content of galena) in barite-galena assemblages can be used to define the oxygen fugacity during ore formation. A relation is derived linking the activity of PbSO₄ molecule in barite (or BaS molecule in galena) and the oxygen fugacity at given temperatures.
Fugacity diagrams for estimating the conditions of formation of various types of barite-galena ores are constructed using this relation together with thermodynamic data for other ore minerals.
As an application, the lead contents of barites from some Kuroko type deposits are used in an attempt to define the physico-chemical conditions of ore formation.

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