Hidaka Belt Research Articles

Carbon contents of the magnetite-series and ilmenite-series granitoids in Japan.

Representative magnetite-series (n=75) and ilmenite-series (n=143) granitoids, and metamorphic rocks (n=11) from the Ryoke Belt, Sanyo Belt, Sanin Belt, Hidaka Belt, Outer Zone of Southwest Japan and Green Tuff Belt, were analyzed for total and noncarbonate carbon contents by combustion and infrared absorption photometry. Noncarbonate carbon contents of the ilmenite-series granitoids (58 and 61 ppm in the average for granodiorite and monzogranite, respectively) are slightly higher than those of the magnetite-series granitoids (39 and 35 ppm), especially of the sodic type (13 ppm for tonalite). Some ilmenite-series granitoids have noncarbonate carbon contents as high as 200-300 ppm at few places. In the carbonate vs noncarbonate carbon contents diagram, common ilmenite-series granitoids have values between those of the sodic granitoids and metamorphic rocks indicating that the ilmenite-series granitoids were formed by mixing of both the igneous and sedimentary source materials. A rather ambiguous separation of the magnetite series from the ilmenite series in these contents may also be due to remobilization of carbon after the granitoids solidified.

Metamorphic evolution of the southern part of the Hidaka belt, Hokkaido, Japan

Abstract The Hidaka metamorphic terrane in the Meguro‐Shoya area, Hokkaido, Japan is divided into four progressive metamorphic zones: A—biotite zone; B—cordierite zone; C—cordierite–K‐feldspar zone; and, D—sillimanite–K‐feldspar zone of the andalusite–sillimanite facies series type of metamorphism. The metamorphic grade ranges from the higher temperature part of the greenschist facies (zone A) through the amphibolite facies (zones B and C) to the lower temperature part of the granulite facies (zone D). The zone boundaries intersect the bedding planes at high angles. P–T conditions estimated are 450–550°C and 2 kbar for zone A, 550–600°C and 2–2.5 kbar for zone B, 600–650°C and 2.5–3 kbar for zone C and 650–750°C and 3–4 kbar for zone D. The metapelites of zone D were partially melted.At the later stage of the regional metamorphism which is early Oligocene to early Miocene in age, cordierite tonalite and biotite tonalite intrusives associated with segments of the highest grade rocks (zone D) were emplaced into the lower temperature part of the regional metamorphic rocks, giving rise to a contact metamorphic aureole. The thermally metamorphosed terrain (zone C') belongs to the amphibolite facies and its P–T conditions are estimated to have been 550–700°C and 2 kbar.The P–T–t paths of the Hidaka metamorphism show a thickening–heating–uplifting process. The metamorphism is inferred to have taken place beneath an active island arc accompanied by partial melting of the crust.

Deformation structure of the "Uenshiri Horst" in the Hidaka Belt, central Hokkaido

Deformation structure of the "Uenshiri Horst" in the Hidaka Belt, central Hokkaido

The Neogene tectonics of the Shikaribetsu district in the Hidaka Belt, Hokkaido, Japan

The Neogene tectonics of the Shikaribetsu district in the Hidaka Belt, Hokkaido, Japan

The Hidaka Shear Zone (Hokkaido, Japan): Genesis during a right‐lateral strike‐slip movement

The Mesozoic structure of Hokkaido, which is characterized by a wide spread ophiolite sequence unconformably overlain by a Cretaceous flysch sequence, is cut by a north‐south trending metamorphic belt, the Hidaka Belt. This contribution aims to demonstrate that the Hidaka Belt is a wide right‐lateral strike‐slip shear zone. The movement is contemporaneous with the metamorphism and the magmatism of Oligo‐Miocene time.

十勝平野の構造発達史 帯広盆地と幕別台地の分化

The purpose of this paper is to report the stratigraphy, age and tectonic movement of the Pliocene-Late Pleistocene deposits on the Makubetsu Plateau in the central region of the Tokachi plain on the basis of the geological relations of these deposits and K-Ar age data of the pyroclastic materials and obsidian pebbles collected from 8 horizons in these deposits.1. The Tokachi Super Group, Pliocene-Early Pleistocene, distributed in this Plateau, is divided into the Ikeda and the Osarushinai Formations in ascending order. According to the molluscan and foraminiferal fauna, paleomagnetic stratigraphy and K-Ar age data, the age of the Ikeda Formation is correlative to the latest Pliocene, and the Osarushinai Formation to Early Pleistocene. The Osarushinai Formation, composed of clastic and pyroclastic materials, was accumulated in shallow sea and terrestrial basin formed subsequently by the westerly shifting of the center of the Ikeda depositional basin.2. The Makubetsu Plateau was transformed into an upheaving area after the deposition of Osarushinai Formation, while the Obihiro Basin remained as a relatively subsiding area. Along the western margin of the Makubetsu Plateau runs an active tectonic line called Oribe Fault.3. It is noticeable that the thick fanglomeratic deposits, the Kochien Gravel Bed, prevail throughout this Plateau. The lithofacies of this Gravel Bed suggest that the western hinterland, Hidaka Belt, was eroded away vigorousely in Middle Pleistocene. Some younger gravels and pyroclastic deposits cover the dissected Kochien Gravel Bed. Those younger gravel deposits are fan-surface deposits formed by erosion and resedimentation of the older thick gravel bed.4. The areal changes in the altitudes of both the upper surface and the basal level of the Kochien Gravel Bed in and around this area have been critically analyzed to detect the Late Pliocene to Holocene tectonic movements which displaced and deformed this gravel bed. It has been disclosed as a result of this study that the activity of the Oribe Fault has a right-lateral strike-slip component and shows a vertical component decreasing gradually since Early Pleistocene. Moreover, it is worth notice that the Oribe active fault appears to have originated along the boundary between the Hidaka and Tokoro belts.

Petrological significance of granitic inclusions from Pliocene-early Pleistocene pyroclastic flow deposits in central Hokkaido, Japan.

Mineral and chemical compositions of granitic inclusions in the Pliocene-early Pleistocene rhyolitic pyroclastic flow deposits of central Hokkaido are very similar to those of the host rhyolitic pyroclastic flow deposits, but different from those of the basement Tertiary granites. The Sr isotope ratios of both of the pyroclastic flow deposits and the granitic inclusions range from 0.7032 to 0.7040, which are notably lower than those of the Tertiary granites (0.7050-0.7054) and the metamorphic rocks (0.7044-0.7071) of the Hidaka Belt. Such evidence indicates that the granitic inclusions are not derived from the basement rocks, but are co-magmatic with the rhyolitic pyroclastic flows. The water vapor pressure and temperature of the magma which produced both the rhyolitic pyroclastic flows and the granitic inclusions are estimated to be 1 kb and 600°-750°C. Hence, it may be interpreted that the rhyolitic pyroclastic flows are eruptive equivalents of a shallow granitic pluton. The low Sr ratios suggest that the source material of the volcano-plutonic association may not be ascribed to the older upper crust, but to a certain kind of lower crust or upper mantle material.

The Miocene upheaval of the Kitami-Takinoue region, northern part of the Hidaka Belt, Hokkaido, Japan

The Miocene upheaval of the Kitami-Takinoue region, northern part of the Hidaka Belt, Hokkaido, Japan

西南日本外帯と北海道日高帯の花こう岩類の主成分化学組成による比較

About 320 Tertiary granitoids from the Outer Zone of southwest Japan and the Hidaka Belt of central Hokkaido are statistically compared on major element chemistry. These granitoids occur along the tectonic zones facing fore-arc basin, and have similarities in geological age and opaque mineralogy (il-series). The main conclusions are as follows: (1) The granitoids from the Hidaka Belt are similar to those from the Outer Zone of southwest Japan, being rich in K2O and FeO but poor in CaO and Fe2O3 compared with the average of Japanese granitoids (Aramaki et al., 1972). (2) A considerable difference, however, is noted in Na2O content between granitoids of both regions. The granitoids of the Hidaka Belt have higher Na20 content than those of the Outer Zone of southwest Japan. The sodic character of granitoids in the Hidaka Belt may be ascribed to the sodic nature of the source material which is the sedimentary and metamorphic rocks of the Hidaka supergroup that contained originally abundant volcanic materials. The granitoids of the Outer Zone of southwest Japan may have interacted with both the gneissic basement and the Shimanto supergroup having low Na2O and high K2O contents. (3) TiO2 content of granitoids from both zones are higher than the average of Japanese granitoids. (4) Al2O3 content of the granitoids of the two zones is similar to that of the Japanese average, but their excess Al2O3 calculated as normative corundum (corundum index) is higher than the average. (5) In the Hidaka Belt, occurrence of S-type granitoid besides I-type one is suggested from the major element chemistry, which is consistent with recent finding of cordieritebearing granitic rocks from this belt.

Geological evolution of Hokkaido, Japan: an example of collision orogenesis

In the Cretaceous, the Yezo arc-trench system was developed along the eastern margin of the Siberian continent, in a forearc basin and inner trench slope to trench environments. The earlier-formed Kamuikotan metamorphic rocks constituted a part of the trench-slope-break of the Yezo forearc. The Sorachi Group (late Permian to early Cretaceous), made up of oceanic pillow lavas, basic tuff, diabase and chert occupied the eastern margin of the Yezo System: it was covered by the Yezo turbidites which were supplied from the west. Across the Sorachi ocean, the Okhotsk continent to the east supplied clasts westwards to form the Hidaka Supergroup. The oceanic part of the Hidaka Supergroup is equivalent to the Sorachi Group. In the latest Cretaceous, the Yezo forearc basin was filled up and coal-bearing Palaeogene deposits were developed there. The Okhotsk continental block moved westward and rotated clockwise, finally colliding with the Yezo arc-trench system in the Miocene, causing the Hidaka orogenesis. The collision took place first at the northern margin and then gradually further southwards, because conglomerates (supplied from the Hidaka uplifts generated by the collision) appeared first in the north and later in the south. In front of the collision suture, enormous amounts of gravity-flow deposits were developed, which are represented by the Miocene Kotanbetsu Formation in the northern part of Hokkaido and the Kawabata Formation in the south. This collision was followed by the development of the proto-Kurile Trench, which is related to the 36-30 Ma and later magmatism in the Hidaka Belt and Oshima Peninsula.

Slump beds in the Hidaka Super Group, northeastern Hidaka belt, Hokkaido

Slump beds in the Hidaka Super Group, northeastern Hidaka belt, Hokkaido

Neogene Tertiary System in the northern part of the Hidaka Belt, Hokkaido, Japan

Neogene Tertiary System in the northern part of the Hidaka Belt, Hokkaido, Japan

Petrological study of the sandstones in the Pre-Cretaceous Yubetsu Group, northeastern Hidaka Belt, Hokkaido, Japan

Petrological study of the sandstones in the Pre-Cretaceous Yubetsu Group, northeastern Hidaka Belt, Hokkaido, Japan

RIVER TERRACES AND ROCK FLOORS ALONG THE UPPER STREAM OF THE YÛBETSU, HOKKAIDO

Having made a reconnaisance in this area, the writer classified it into several geomorpholoical surfaces, concerning about the nature and the time of the formation of each surface. (1) Those surfaces are termed, from the lower to the upper, A to G, and mountains; and B is subdivided into Ba and Bb. The relative height of A to G is about 250 meters. (2) A•B•C•D are river terraces, while E has characters of the rock bench or the partial pediment (by Ben A. Tator, 1952-1953). F may be the same with E, and a part of D resembles E. Above identification depends on the structures of the superficial layers underlying those surfaces and on the forms of those surfaces. G is the surface of the inselberg-like isolated hill, relating to E and F. (3) The rocks forming mountains are ancient ones of Hidaka Belt, and the rock underlying G is liparite, while the rest on which the large part of each surface-A-F-lie is loose tuffaceous sandstone. (4) Among the materials (gravels or finer materials) underlying Bb and C, various paleolithic. stone implements have been discovered by Shoichi Yoshizaki, archaeologist. (5) The writer takes a view that such stone implements must be embedded in the material underlying Ba. The reason is that Ba and Bb are supporsed to be the protected terraces, owing to the presence of the gorge of the hard rock of Hidaka Belt downstream, and the time of those formation supposed to have been in the same cycle. But an alternative interpretation would be possible, that is, the time of the formation of the graded reach emerged as Ba later belongs to the alluvial epock, but the time of the accident by which Ba was formed belongs to the dilluvial epock. (6) Geologist Kiyoshi Hasegawa has studied the area and, from the gravels underlying each surface, concluded that the time of the formation of the volcano Tengudake corresponds to the time of the formation of C, and that of the present peak of the volcano is later than that of B and earlier than A. The lava flows of the volcano might affect the drainage systems of this area, and they might also affect the agencies to form those surfaces. (7) In addition to the facts above mentioned, there exist another characteristics, that is, each surface has different pedological character. So, the writer supposes that such surfaces could be classified corresponding to the geological age, from the view point of geomorphology, geology, archaeology and pedology. And the conditions, especially climatic ones, under which each surface was formed could be estimated.