Most Tertiary ore deposits in the southern Rocky Mountains are associated with eroded volcanoes or shallow underlying plutons. Distributions and compositions of the igneous rocks vary complexly with time, apparently reflecting evolving boundaries between the American, Farallon, and Pacific plates nearly 1, 000 km to the west. Loci of igneous rocks and associated ores also were influenced by structural zones of Precambrian ancestry, especially the mineral belt of Colorado and the Jemez zone in New Mexico.
In earliest Tertiary time, the southern Rocky Mountains were the site of Laramide compressional tectonics, limited igneous activity, and associated mineralization, all of which appear related to low-angle subduction extending the width of the cordillera. Igneous activity (calc-alkaline, dominantly intermediate compositions) and associated ore deposits (mainly base-and precious-metal veins) were largely confined to the Colorado mineral belt.
After an early Tertiary lull, volcanism, intrusive activity, and mineralization renewed on a large scale about 40 m.y. ago. A composite volcanic field extended across much of the southern Rocky Mountains; associated intrusive rocks range from isolated plutons to composite batholiths that underlie much of the presently high terrain. Compositions of the igneous rocks and associated ores differed little from those of Laramide activity. Some metals were probably derived from the magmas, but others-notably Pb, which is amenable to isotopic tracing-include major components from old upper crustal rocks. The largest erosional remnants of the volcanic terrane lie to the south, notably the San Juan, Thirtynine-Mile, and Latir volcanic fields; to the north, deeper erosion has exposed large mid-Tertiary intrusive complexes in the Sawatch Range and to the northeast along the mineral belt.
This igneous activity constitutes only a small sector of a regional sweep south and west across the cordillera, perhaps related to foundering of the descending Farallon plate as its size, thickness and rate of convergence decreased. About 25-30 m.y. ago, as intermediate-composition activity peaked, compositions became increasingly silicic, and northwest-trending extensional faulting marked inception of the Rio Grande rift. Especially rich ores are associated with such silicic subvolcanic intrusions; some-notably Mo deposits-are clearly derived from the magmas. This association of faulting and silicic magmatism, as exemplified by the Latir volcanic field and the Questa caldera, seemingly represents local expression of widespread inter-and back-arc extension as the subduction zone steepened and migrated westward: significant are coherent patterns of southward migration of silicic igneous activity and of northwest-trending normal faults across much of the western United States.
The volcano-tectonic association of the southern Rocky Mountains changed further after about 20 m.y. ago. Volcanism became dominantly basaltic or bimodal basaltic-rhyolitic, and dominant trends of normal faults shifted to nearly north-south, the trend of the modern Rio Grande rift, by about 5-10 m.y. ago. This association now characterizes much of the western United States, reflecting increasing interaction between Pacific and American plates along the San Andreas transform. Thus, igneous and structural patterns in the southern Rocky Mountains are local expressions of trends and sequences that affect the entire cordillera, a relation that supports platetectonic interpretations of the evolution of the southern Rocky Mountains despite great distance from the plate margin.

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Kuroko-type massive sulfide deposits exhibit similarities to certain epigenetic polymetallic Cordilleran deposits in base metal ratios, paragenesis and time-space association with felsic magmatism. In addition, the transport and deposition of Kuroko-type ores occurs within seawater-dominated convective systems.
Consideration of empirical data from the Taupo Volcanic Zone, New Zealand indicates strong similarities to the general setting of Kuroko ore deposition, and implies large volumes of intrusive magma to provide the necessary heatflux.
The metal content of certain postmagmatic fluids and δD constraints on Kuroko-type ore fluids suggest a model for Kuroko-type ore genesis in which host-rock leaching is not the major source of the metals involved. The preferred model envisages a magmatic source for the bulk of the metals in Kuroko-type ores, with the overlying convective systems acting as focussing mechanisms for ore fluid discharge and as contributors of reduced sulfur for metal sulfide deposition.

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The 31 samples were taken from footwall dacite around Fukazawa kuroko deposits to be analyzed 13 elements. DATE and TANIMURA (1973) estimated the amount of mobile components as AL₂O ₃ were supposed to be inmobile. As correlation coefficients between immobile components should be very high (FONTEILLES, 1976; IIYAMA et al, 1980), the ratio of each mobile components to sum of immobile components can be compared with that of calc alkali Quaternary volcanic rocks in this area to estimate quantitatively mobile components.
After checking correlation coefficients among 13 components, 3 components (AL₂O ₃, TiO₂ and total Fe) were chosen as the immobile components. And the result of comparison with Quaternary volcanic rocks is as follows; in the neighboring area of kuroko deposits, addition of MgO and Fe₂O₃, depletion of FeO and Na₂O, and little change of total Fe are observed, on the other hand addition of Na₂O and SiO₂ can be seen in the area far away from kuroko deposits.

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Vein systems of the Akenobe Cu-Pb-Zn-W-Sn deposit, Hyogo Prefecture, are devided into two types, i.e., B-type and D-type based on their fracture patterns (Fig. 3) and modes of emplacement (Fig. 4). The system of B-type consists of veins whose strikes are N10-20°W, N40-50°W and N70-80°W, and the boundary between a vein and a country rock is clear. Most of veins in the Sekiei area, and Shirogane veins in the Kanagidani area belong to this type. On the contrary, the system of D-type is not characterized by the distinguishable strikes, and is accompanied with disseminated ores along a vein. Chiemon veins in the Daiju area, and Ginsei veins in the Kanagidani area belong to this type. Rock mechanics suggests that the veins of B-type were formed by the brittle failure of country rocks, and that those of D-type by the ductile deformation. This implies that we must take into account the ductile behavior of rocks as well as brittle one for discussion on the formation mechanism of fracture systems.

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The Kishu copper mine is located in the northern part of the Kumano coalfield in the outer zone of Southwest Japan. Veins of xenothermal type occur in the Miocene sediments, which contain coals and fine particles of dispersed carbonaceous matter. The coals were formerly worked at the Yakushi, Miyai and Shiko coal mines near the Kishu mine. The samples studied were collected from the underground of the Kishu mine, old mine dumps and cores of two boreholes.
The Miocene sediments were intruded by the Kumano Acidic Rocks and the related igneous rocks in the middle Miocene time. Vitrinite near the contact with the intrusive bodies was converted to natural coke with mosaic, flow and spherical structures. The structures of coked vitrinite indicate that vitrinite was of bituminous rank at the time of intrusion. It is apparent from the general pattern of the isoreflectivity lines in the area that the hydrothermal mineralization followed the intrusion and altered bituminous rank of vitrinite to anthracite which ranges in maximum reflectivity from 3 to 6.5 percent.

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The cupriferous massive sulphide deposits of Shimokawa occur in the Hidaka Series consisting of basaltic pillow lava, diabase, gabbro and serpentinite with intercalations of slate and sandstone of Pre-Cretaceous age. The structure of the Hidaka Series strikes generally NNW and dips to ENE at 50°-70°. The cross lamina and graded bedding in the sedimentary rocks and the downward protrusion of the pillow lavas indicate always that the strata are overturned.
The mafic and ultramafic rock series in this area might be regarded as an overturned ophiolite complex, although it intercalates slate and sandstone.

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Cretaceous granitoids distributed around the Akenobe mine area have received pervasive propylitic alteration at many places. Unaltered granites of the Wadayama and Hikihara plutons, which belong to the ilmenite-series and are considered to be the related granite to the Cu-Sn stage mineralization of the Akenobe tinpolymetallic vein deposits, contain an average of 6.0 ppm Sn: whereas the altered granites have only 1.7 ppm Sn in the average. This result supports the model that the meteoric-water mixing leached out tin from the granitic rocks, and the then-formed ore solution was brought up to the site of the Akenobe ore deposits (ISHIHARA et al., 1981). The magnetite-series granitoids (the Shiso granitic complex) distributed to the southwest of the Akenobe mine are always low in tin. This tendency is observed elsewhere in the magnetite-series granitic terrains in Japan (ISHIHARA and TERASHIMA, 1977). These granitoids should not be considered related to the tin mineralization.

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