Lead isotopic data of high precision on some epigenetic hydrothermal deposits-recently shown to be in terrains containing Proterozoic cobbles-confirm previous studies that much of Japan is primarily a continental feature. Further, the low values of ²⁰⁶Pb/ ²⁰⁴Pb accompanying high values of ²⁰⁸Pb/ ²⁰⁴Pb in Tertiary (kuroko) deposits of the submarine volcanic exhalative type and epigenetic hydrothermal deposits of Japan are pointing towards the presence of a rejuvenated craton, perhaps as old as 1000 m.y. or greater in age. In contrast, previously published lead isotope evidence on pre-Cenozoic stratiform sulfide deposits of Japan (so-called Besshitype deposits) tend to show a more oceanic mantle character for a part of Japan. Japan, therefore, appears to have a full spectrum of plumbotectonic environments.

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In earlier papers the author has reported that porphyry copper deposits in the southwest Pacific island arcs strongly favour a compressional stress environment, such as plate collision zones, while kuroko and related volcanogenic massive sulphide deposits favour extensional horizontal stress environment. In this paper he attempts to show how the physical and chemical effects of tectonic stress are implicated to metallogenesis.
The following series of hypotheses has already been put forward as a result of the recent accumulation of more accurate in-situ stress measurements in some deep mines, drill holes and other suitable locations, together with theoretical investigations based on these observations (Fig.1). Some of them are taken up here as;
(1) The orientation of one of the principal stresses can generally be assumed to be vertical or its close proxmity, and has the value of ρgH (load exerted by the overlying rock formation), as an approximate average (Fig.1, Table1).
(2) In the intensively compressional horizontal stress regime, both maximum and minimum horizontal stress, σHmax and σHmln, have a greater value than virtical stress, σ_v_??_ρgH and the stress gradient by depth is also greater than that of ρgH. In the extensional deviatoric horizontal stress regime, on the other hand, the value of the two principal horizontal stresses and their gradient by depth are smaller than ρgH (Fig. 1, Table 1).
(3) At shallow depth of the crust, i.e. 5 to 6 km, where actual in-situ stress measurements are only available, Heim's rule of the lithostatic pressure of ρgH for all three pricipal stress directions has not been observed. Instead, the difference of the values of three principal stresses increases with depth. Thus it is thought that the lithostatic state represent the non-deviatoric normal stresses and the departure from this state indicates the deviatoric stress available to drive geologic deformational processes such as folding and faulting.
Stress acting upon and arbitrary point in the crust (Fig. 2) can be expressed as a matrix formula
which can be resolved to non-deviatoric and deviatoric stress components as follows;
Non-deviatoric Deviatoric
Deviatoric stress will cause ductile deformation in an orogenic region to certain extent depending upon the amount of shear stress (σ ₁₁-σ ₃₃/2 in Fig. 3-A). In the case of a shallow intrusion of a small magma mass this deformation is well represented by several examples in Figure 5. The direction of the maximum horizontal stress is also noted. By the slow ductile deformation in geologic time such as illustrated above, stress will reach to certain equilibrium when P in the matrix above, which is the normal stress acting equally on 3 principal stress axes, reaches to the mean normal stress σ ₁₁+σ ₂₂σ ₃₃/3. This P is assumed as a hydrostatical confining pressure acting on the intruded magma mass instead of pgH, Heim's lithostatic pressure (Table 2). A confining pressure closely regulates inner pressure of an intrusive body of hydrous magma. The author dare to assume, for practical purpose, that the confining pressure can be approximated to the value of magma pressure, at least in the case of the solidification of a hypabyssal intrusive stock of felsic magma (Fig. 4) in an orogenic region.
These two assumptions may often introduce nearly 1 Kbar of pressure difference onto the magma body at the same depth but under different deviatoric stress conditions. In the case of solidification of hydrous magma notable effects caused by the pressure can be anticipated especially in an area of second boiling. How this would control the metallogenesis particularly in the case of porphyry copper was investigated and described in the latter half of the paper.

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Unconsolidated sediments change into sedimentary rocks through their burial diagenetic processes, during which their physical and chemical properties being significantly modified or evolved. For realizing the initial nature of a given sedimentary geologic body, therefore, it is fundamentally required to date back and reconstruct its diagenetic modification or evolution history. In studies of kuroko ore genesis, however, little attention seems to have been paid to this aspect. Our careful observations and re-examinations on the mode of occurrence of the Shakanai kuroko deposits are disclosing some distinct diagenetic phenomena fosslized in them. In the present paper are described some of the results obtained, their genetic significance being discussed in the forthcoming, paired paper. Some of the important facts described here are enumerated as follows:
(1) The Shakanai deposits are composed essentially of a number of massive "ore-lumps" with various dimensions and of relatively low-grade matrices cementing them. The deposits, as a whole, constitute a bedded form to be emplaced within a single stratigraphic horizon.
(2) The ore-lumps are in most cases oval or lenticular and sometimes breccia-like in shape, the breccialike ones being restricted in occurrence to some clayey sheared zones in which "slicken-side" are well developed.
(3) Alternation of thinly bedded ores and mudstones rather commonly occurs in places, and a number of small ore-lumps are also sometimes arranged in layer conformably within mudstone beds. So-called "load-cast" structures are usually developed between the unit beds of ores or mudstone.
(4) In ores of the deposits are rather extensively developed some "water-escape" structures, which are very similar in appearance to what have been reported from normal elastic sediments by LOWE (1975).
(5) Thin ore-veinlets with rather irregular geometric patterns are commonly found not only within the massive deposits but also in both hangingwall and footwall rocks. They are generally discontinuous in occurrence and are essentially similar in mineralogical characteristics to the ores surrounding them. In the ore-lumps are also often developed some sort of small pores or openings with irregular shapes, in which idiomorphic crystals of sulfide and/or gangue minerals are sometimes observed.
(6) Ore microscopically, so-called "colloform textures" are found to exist extensively throughout the deposits, from the lower pyritic ore zone to the upper black-ore zone. The most characteristic of them is of pyrite, showing a series of textures evolving from very minute globular particles of about 1 micron or less in size, via framboidal aggregates of the minute particles, to coarser crystal aggregates including those relatively more primitive textures.

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The present study is an attempt to work out the geology and geological structure, especially the stratigraphy and historical geology of the Tertiary of the marine region situated between the Sakito-Matsushima and Takashima Coalfields located in the sea west of the Nishisonogi Peninsula, Nagasaki Prefecture.
No geological information on this area has been available up to the present, but geophysical prospecting and drilling investigations (Figs. 3 and 4) have shown the existence of a coal einbeded Paleogene Systems having sediments correlated to the Tertiary in the Sakito-Matsushima and Takashima Coalfields (Figs. 1 and 2) considered to be submarine coalfields. Accordingly, all these coalfields have been collectively designated as the Nishisonogi Coalfield by the author. The study on the history of its formation and development are presented in summary as follows:
(1) Based on the main features of basements such as Nomo Peninsula, Barriers of Mitsuse, Miezaki and Terashimaoki, the sedimentary basin of this area may be divided into a number of depressions where the formation of the Nishisonogi Coalfield began in the late Mesozoic Era by local sedimentation action of the Mitsuse Formation and reddish purple beds and coaly shale. (Figs. 6, 7-1 and 7-2). This was followed by the Paleogene sedimentation period during which repeated unification and separation of the depression took place accompanied by movement of each barrier. However, it is concluded that the sedimentation gradually extended from the south to the north.
(2) During the Terashima Age (Fig. 7-3) in the Paleogene sedimentation period, the central coalfield was an uplift belt, and the south side area of the coalfield was environment preferable to the formation of coal seam. In the succeeding Matsushima Age (Fig. 7-4), the uplift belt caved in and the south side of the coalfield became a marine environment and the conditions became favorable for extensive coal sedimentation on the north side between the Sakito-Matsushima and Ikeshima terrains.
(3) In the Nishisonogi Age (Fig. 7-5), the area of the sedimentary basin of this coalfield markedly increased, and extended to the sea region. Not only did the formation of the coalfield cease on the north of the uplift belt in the central coalfield, but also brine water intruded to some extent into the Nishisonogi Peninsula where the Nishisonogi Group had deposited. The northern boundary of this Nishisonogi Sea extended to the Sasebo Coalfield.
(4) The northeast boundary of the Nishisonogi Coalfield is cut by a basement fault (Yobuko-no-Seto Fault) whose continuous activity before and after the Tertiary sedimentation has played an important role in the coalfield formation. The normal and reverse faults, and folding in the Tertiary period also aided the basement in forming a buried hill, thus causing the barriers to become extinct. This greatly influenced the formation of the coalfield.
(5) This coalfield is of moderate scale compared with other coalfields in North Kyushu. Nevertheless, it has existed over a long period of time from the Mitsuse Age in the late Mesozoic to the sedimentation of Nishisonogi Group, whose formation history itself may be considered to be a representation of the historical geology of the coalfields in North Kyushu.

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Tungsten replacement deposits fall into two general types: W-Mo-Cu types occur in oxidized (Fe ³⁺/Fe ²⁺ generally>1.0) skarns whereas W-Sn-F types occur in reduced (Fe ³⁺/Fe ²⁺ generally<1.0) skarns. These are related to the oxidized "I-type" granitoids and the reduced "A-type" granitoids respectively. In W-Mo-Cu skarns, interaction of ore solutions with low fo2 wall rock and/or later hydrous alteration overprints may result in lower Fe ³⁺/Fe ²⁺ but the main metallogenic characteristics of the skarn persist. Most of the world's largest tungsten deposits are W-Mo-Cu type skarns whereas the W-Sn-F skarns are usually of limited extent and commonly related to other styles of W-Sn-F mineralization such as quartz veins and greisens.

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