The Hisatsu volcanic province is a northward curved belt of about 100 km in length from northwest to southeast and 25 km wide in the northern part of Southern Kyushu. In this province, the volcanic rocks (Hisatsu volcanic rocks) are continuously distributed throughout most areas with an average thickness of more than 400 m. The volcanic activity in this province occurred in the period from late Miocene to middle Pleistocene. It is divided into three stages based on stratigraphy, lithology, age and mode of occurrence of rocks. In the first stage, the Hisatsu volcanotectonic depression was formed and a large amount of andesitic tuff breccias and some lavas erupted in the depression from 7.6 Ma to 2.5 Ma. In the second stage, andesite lavas formed vast plateaus (flood andesite) during the late Pliocene (2.5 Ma to 2 Ma), and in the third stage from 2 Ma to 0.4 Ma, there were continuous eruptions of the flood andesites. The volcanic rocks of these stages were distributed in all areas of the Hisatsu volcanic province.
     The Hisatsu volcanic rocks are divided into low-potassium (low-K) and high-potassium (high-K) andesites based on chemistry and mode of occurrence. In the first stage, the low-K andesites occurred in the west side of the province and the high-K andesites in the east side. In the second stage, the high-K andesites widely erupted throughout the area. In the third stage, the low-K andesites erupted in the west side again, and the high-K andesites in the east side. In this stage, the low-K andesites also occurred at the easternmost area of the Hisatsu volcanic province. It is thus deduced that the centers of volcanism of the low-K andesites and the high-K andesites existed at west and east, respectively. The volumes of ejecta in the first, the second and the third stages were estimated at about 390, 110 and 60 km³, respectively. The gross volumes of low-K andesite and high-K andesite over the three stages were estimated at about 336 and 224 km³, respectively. Three kinds of parental magmas (high-K high-magnesian andesite, low-K high-magnesian andesite and tholeiite magmas) and four trends of fractional crystallization are recognized in the Hisatsu volcanic rocks. The Hisatsu volcanic activities have some characteristics differing from those of subduction zone magmatism, so it is assumed that the Hisatsu volcanic rocks originated from an ascending heterogeneous mantle. The Hisatsu volcanism represents a main part of the activity involving the upwelling of a 100 km diameter mantle in Southern Kyushu.

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福岡県南部に位置する星野金鉱床西部地域には後期新生代の火山岩類が分布し，これらに含金銀石英脈が胚胎している。最近，大規模なシリカシンター群が発見され，新たな金鉱床の存在が期待されている。本地域の地質や火山層序については不明な点が多く，さらに火山岩や鉱脈の生成時代はほとんど分かっていない。本研究では当地域の地質の再検討を行うとともに，各火山岩類のジルコンを用いたフィッション·トラック年代測定を行った。
   当地域の火山活動の開始時期は中新世と考えられていたが，基盤岩類を直接覆う火山層序最下位の星野安山岩は4.3 Maを示した。この値は誤差が大きいものの年代試料への熱水変質の影響は見られない。したがって当地域の火山活動の開始時期は鮮新世初期と考えられる。その上位の鉱脈の母岩となる池の山礫岩と釈迦岳安山岩の年代は得られなかったが，さらに上位の霊岩寺安山岩は3.2 Maを示した。これらは2.8∼2.6 Maのほぼ同時期を示す竹山安山岩，日向神デイサイトおよび黒木流紋岩に被覆される。以上の結果よりこの地域の火山活動は鮮新世に限られることが明らかになった。時空分布を考えると本地域の金鉱化作用は，アダカイト的な組成を有する竹山安山岩との密接な関係が示唆される。
   Hohi豊肥，Hyugami日向神，Shakadake釈迦岳，Taio鯛生，Reiganji霊岩寺

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