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３つのプレート境界において，沈み込み帯が最も重要な役割を果たしている。日本の地質学者は，2010年までは沈み込み帯での付加作用に注目してきた。沈み込み帯では，付加作用と構造侵食作用の両方が起こっているが，付加体が25％，構造侵食が75％の比率となっている。近年，構造侵食作用の重要性が認識されてきた。本論文では，沈み込み帯における付加作用と構造浸食作用の地質学的意義をまとめた。, A plate boundary of subduction zone plays the most important role among 3 type boundaries. Japanese geologists had been concerned to reveal an accretionary mechanism at the subduction zone until 2010. Even though both functions of accretion and tectonic erosion occur, they are 25 % and 75 % respectively of all subduction area. Recently, it has been recognized that tectonic erosion is more important function than accretion. In this paper, the geological characteristics of accretion and geological significances of tectonic erosion at a subduction zone was reviewed., 論文, Article

四国西部、幡多半島東岸地域の後期漸新世～前期中新世の清水層・在岬層の混在相は、火山礫岩や火山性砂岩、含火山岩礫泥岩などの火砕岩を含む。火砕岩は、中期始新世の石灰岩を伴うことがある。火砕岩の多くは、土石流や乱泥流などの堆積物重力流に由来する。火砕岩中の火山岩は、アルカリ岩系の火山岩であり、アルカリ玄武岩、粗面安山岩、粗面岩およびコメンダイトからなる。アルカリ玄武岩や粗面安山岩には緑泥石や方解石で充填された発泡痕を有する。アルカリ玄武岩にはカンラン石仮像が含まれる。火山岩類はかなりの程度の変質作用を被っており、ほとんどの苦鉄質鉱物は、緑泥石などの粘土鉱物やFe-Ti酸化鉱物で置換されている。変質過程での移動が少ないと考えられる元素を使ったいくつかの判別図から、火山岩は海洋島起源のプレート内アルカリ岩と推定される。後期漸新世～前期中新世のある時期に四国西部の収束域で海山の衝突があったと考えられる。

Jurassic subduction complexes of the eastern part of the MinoTerrane, central Japan have been divided into six complexes on the basis of lithology and structure. Among them, the Misogawa Complex is the youngest in age of accretion in the eastern part of the terrane and is situated in the structurally lowest part of the subduction complexes. The Misogawa Complex in the Otaki area is mainly composed of sandstone, mudstone and chert and accompanied by siliceous mudstone and claystone. Although sedimentary structures are well preserved in some cases, the rocks are generally deformed to various degrees. Sheared and chaotic pebbly mudstone with clasts of chert and sandstone is common in the complex. Radiolarian fossils indicate that the pelagic environment of deposition continued to middle Middle Jurassic time at least and that the final depositional age of the complex was late Late Jurassic time. The complex is subdivided into five tectonic units in fault contact with each other. The trend of upward-coarsening from pelagic chert to detrital sediments in each unit is cnsistent with the lithological change in the chert-elastics sequence that chracterizes less deformed subduction complexes within the Mino Terrane. The Misogawa Complex in the study area forms a paired synform and antiform plunging to the northwest. The asymmetry of the folds and the age of intrusives after the folding, indicate that the complex has undergone sinistral shear in late Early to early Late Cretaceous time., Article, 信州大学理学部紀要 34(1): 25-50(1999)

Volcanic rocks were found at Eurasian side slope of Suruga Trough convergent plate boundary by dive 708 of the "Shinkai 2000". These volcanic rocks crop out at the eastern lower slope of the Senoumi North Bank at a water depth of 1,500 m. Two types of phyric andesite rocks, hypersthene-augite-andesite and hornblende-augite-andesite, were noticed, both containing distinctly large phenocrysts. These volcanic rocks overlie the conglomerate layers that date from 0.91 to 0.82 Ma within nanno fossil biostratigraphic horizon CN 14 a, so the age of igneous activity may be a little yonger than the nanno fossil age. The volcanic rocks have strong similarities with regard to the rock types, geological situation, and stratigraphic relations to the rocks of the "Iwabuchi pyroclastic rocks and Iwabuchi volcanoes group". These rocks cover Kambara Conglomerates at Kambara Hills 45 km to the north of this site. Nanno fossil age obtained from a muddy layer intercalated in "Iwabuchi pyroclastic rocks" is 0.92-0.46Ma, and the "Iwabuchi pyroclastic rocks" indicate paleomagnetic reversed polarity. So the volcanoes in the Suruga Trough area would be active in the later part of the Matuyama reversed magnetic polarity chronozone and also be younger than the Jaramillo sub chronozone of 0.92 Ma. The rock samples of hornblende-augite-andesite are conspicuously reddish-purple due to hematite micro crystals scattered through the groundmass and also replacing the phenocrysts, and hornblende phenocrysts are severely opacitized oxyhornblende. These facts suggest that the volcanic activity happened under an oxidizing environment, so the eruption might be aerial or in very shallow sea. The tectonic situation and geological environment would be very different from the persent, and more than one thousand and several hundred meters depression has occurred since then. Further research about convergent boundary volcanic activity is necessary not only for local geological interest but also for solving fundamentally important problems of tectonic history of the whole Suruga-Nankai Trough region and tectono-magmatic phenomena.