Ferroaxinite and datolite occur in veins in a dolerite sheet cutting metabasite of the Setogawa Group. The chemical analysis of ferroaxinite is SiO₂ 42.40,Al₂O₃ 18.30, Fe₂O₃ 0.09, TiO₂ 0.13, FeO 9.05, MgO 1.51, MnO 0.77, CaO 19.20, B₂O₃ 6.37, H₂O^＋ 1.33, H₂O⁻ 0.06, total 99.21% corresponding to (Ca_1.94Mn_0.06)_Σ2.00 (Fe^2＋_0.71Mg_0.21Al_0.04Fe^3＋_0.01Ti_0.01) _Σ0.98Al_2.00B_1.04Si_4.00O₁₆H_0.84 on the basis of total O = 16. The empirical formula of datolite, derived from the chemical analysis, is very close to the ideal formula CaBSiO₅ (OH) with a slight H₂O excess. Idiomorphic forms of the minerals are exclusively found in voids in veins, although partially developed forms of ferroaxinite are common. Ferroaxinite is tabular with larger r(011) and b(010). Datolite idiomorphs are short prisms with m(110) and s(102) dominant. Associated minerals within and adjacent to veins are quartz, calcite, albite, adularia, chlorite, and bannisterite, together with pumpellyite. In veins ferroaxinite always preceeds datolite in the crystallisation sequence. This is similar to the relationship between manganaxinite and datolite in skarns from some pyrometasomatic ore deposits in Kyushu. Some veins lack ferroaxinite and have pumpellyite instead, drawing attention to the fact that, leaving aside minor differences in H₂O content, subtraction of HBO₂ + SiO₂ from the ferroaxinite formula yields pumpellyite-(Fe^2＋).

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The Auckland field has been active for over 140,000 years, during this time eruptions have formed 49 small volcanoes. The magmas which have fed the field range from alkali basalt to nephelinite but the most recent eruption has been of transitional to tholeiitic basalt. Each eruption has involved a new batch of magma to produce volcanoes that are monogenetic in character. Detailed work on the erupted deposits show that the two main types of activity from the field have been magmatic and phreatomagmatic. The particular type of activity in an eruption is controlled by the water : magma ratio. In "dry" conditions, strombolian and hawaiian eruptions occur. At low water : magma ratios, phreatomagmatic eruptions are dominated by pyroclastic fall whereas at high water : magma ratios, phreatomagmatic activity is dominated by base surges. The water required for phreatomagmatic activity is ground-water or surface water. If water is excluded from the active vent and the magma supply is sufficient for continuation, then activity becomes wholly magmatic and can include the effusion of lava flows. The available ages of Auckland's volcanoes together with the volume of material produced in each, show a trend of increasing size with decreasing time. This pattern is interpreted to mean that the Auckland volcanic field is at an early stage in its evolution and that larger eruptions can be anticipated in the future.

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Auckland is the only district in New Zealand that is known to have lava tube caves. Many small cavities and short tube segments have been found within lava flows from several of the small, late Pleistocene-Holocene, basalt-basanite volcanoes of Auckland Volcanic Field. Excavations for construction sites within the city have uncovered, and de-stroyed, many small cavernous features. No large or long lava caves have been discovered. Wiri Lava Cave, imminently threatened by quarrying activities, is rated of international significance, and fourteen other lava caves are considered to be of national importance for scientific, or educational reasons.

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Rangitoto Island is the largest and youngest volcano in the Auckland Volcanic Field, New Zealand. It is the only volcano that produced tholeiitic basalt. All the others are alkali basalt or basanite.
Sixteen young lava flows overlying the older lava flows were mapped on the basis of aerophotographs and field observations. Thirteen samples from 12 lavas from among 17 lava flows (16 young + one old) were analyzed in order to investigate the variation of chemical compositions of the source magma. The compositional variations within Rangitoto basalt is caused by the accumulation of olivine and clinopyroxene phenocrysts.

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ホワイト島火山から1977年の噴火で放出された火山岩塊は，化学組成では，瀬戸内火山岩のカンラン石，単斜輝石，斜方輝石の順に，Mg#が連続的に減少する単斜輝石高マグネシア安山岩に似る．しかし鉱物化学組成はまったく異なり，ホワイト島高マグネシア安山岩は，著しくMgに富み(Fo_92-88)，正規累帯をなすカンラン石と，対照的にMgに比較的乏しく(Mg#=84-73)，逆累帯を示す単斜および斜方輝石をもつ．特に，単斜輝石の核部はMg#が79-75とカンラン石に比べ低く，カンラン石を晶出させたと同一のマグマに由来するとは考え難い．ホワイト島高マグネシア安山岩は高マグネシア玄武岩質マグマとデイサイト質マグマの混合によって生じた．

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The Ohakune crater is one of the parasitic vents around Ruapehu volcano. Olivine andesite and bronzite dacite occur in and around the crater, the eruption of which took place explosively on the flat laharic plain surrounding Ruapehu volcano.
The Ohakune crater rocks contain some phenocrysts of Mg-rich olivine (Fo88) or orthopyroxene (En89), indicating their derivation from the mantle peridotite. The olivine andesites have high contents of MgO (7.3-6.6%) and SiO₂ (55.5-57.4%), similar to magnesian andesites from some island arcs and continental margins. The bronzite dacite also has MgO (5%) despite its relatively high SiO₂ (63.7%).
The high-Mg olivine andesites fall near the area of parental basalts and andesites of very low-K and -Rb in the linear trend of the Tongariro volcanic rocks in the K-Rb relation, whereas the high-Mg dacite is plotted on the area of relatively high-K and -Rb in the same linear trend. The dacite may have formed by contamination (or mixing) of the olivine andesite-forming magma with a high-K and -Rb, felsic crustal material.

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The Cenozoic geological record of New Caledonia contains two autochthonous magmatic associations, the Early Eocene Formation of Basalts and the . Late Oligocene-Early Miocene granitoid suite of the Koum and St Louis areas. New K-Ar dates show that the boninites in the Nepoui region, hitherto thought to be Early Eocene, are Late Oligocene. Allochthonous ultramafic rocks of the New Caledonia Ophiolite were emplaced in the Late Eocene or Early Oligocene. The similar age of the Nepoui boninites and the Koum-St Louis granitoids suggests that they were linked to a short lived subduction event which took place after ophiolite emplacement.

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Waipapa terrane is the exposed basement of much of the central and northern North Island; it has in the past not been readily correlated with any of the terranes recognised in the South Island and southern North Island. Available information about the lithologies and age relations of rocks in the Waipapa terrane are summarised and three -possibly four - different geographically discrete tectonostratigraphic units, correlated with South Island terranes, are recognised:
Omahuta-Puketi area (= Caples terrane) containing volcanogenic greywackes and laminated argillites, cherts, basaltic tuffs and volcanics of Late Paleozoic age, metamorphosed to prehnite-pumpellite and pumpellite-actinolite facies and uplifted before Mid Jurassic. Bay of Islands - northern Waipapa area (= Older Torlesse/Rakaia subterrane) of feldspathic sandstones exposed in western Bay of Islands and interleaved with argillites and lithic sandstones in the eastern Bay of Islands. Permian microfossils occur in some terrigenous argillites and in tectonically interleaved oceanic limestones and cherts. Compared with the extent of the South Island Rakaia subterrane the northern Torlesse is a very thin sequence; it is believed that the Torlesse has been tectonically thinned out by a series of imbrication zones parallel to Northland Peninsula and does not extend further to the north of New Zealand.
Helena Bay-Hunuas and Moehau-Morrinsville areas which both contain sediments of Upper Jurassic to ? Cretaceous in age, although precise ages and hence stratigraphic relationships are unknown; they are correlated with the Younger Torlesse or Pahau subterrane. However, there are significant differences between the areas: Helena Bay-Hunua rocks are a turbidite sequence containing volcaniclastic sandstones and interleaved basaltic and associated oceanic sedimentary material of Triassic-Jurassic age.
Moehau-Morrinsville rocks are dominated by coarser sandstones and argillite conglomerates and lack oceanic material; they are tentatively interpreted as a terrane collision facies blanketing zones of imbrication and younger than the Helena Bay-Hunuas facies.
Use of the term Waipapa terrane should be discontinued and Caples, Older Torlesse (Rakaia subterrane) and Younger Torlesse ( Pahau subterrane) used instead.

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Heavy fractions of minerals in the sandstones from the Torlesse terrane are composed mainly of metamorphic minerals such as epidote, titanite and pumpellyite with subordinate amounts of detrital minerals such as zircon, garnet, apatite and ilmenite. Although metamorphism has been considered to be continuous within the Torlesse terrane, modal proportions of metamorphic minerals, especially pumpellyite and epidote, are depleted in the centreil region.
Compositions of detrital garnets vary consistently with the geological age of their host sandstones. Jurassic-Cretaceous sandstones contain garnets with a wide compositional range, whereas garnets in Triassic rocks have a narrow compositional range. Rocks of both ages contain Mg-rich and Ca-rich garnets, whereas Permian gar-nets are usually rich in Mn. Although dissolution of garnets is common in the sandstones due to diagenesis and metamorphism, the difference of the garnet com-position reflects compositional differences in the source rocks. Garnets in the Permian rocks were predominantly derived from granitic rocks, whereas those in the Triassic to Cretaceous rocks were derived from garnet amphibolite and gneiss which should be lower in metamorphic grade than metamorphic rocks in the eastern Antarctic.

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Clear and chalky varieties of gismondine are described from vesicles and small dykelets penetrating a basic andesite flow in the Aranga area of Northland, New Zealand. X-ray diffraction, Fourier transform infra-red and thermal data are used to characterise these two varieties (clear and chalky). Results show that despite differences in physical appearance there appears to be no significant chemical difference between the two varieties. However, the chalky variety contains* more low-temperature water, has more Al and less alkalies than the clear variety.

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At temperatures below 300°C restricted areas of metastable solid solution exist in the bornite(bn)-chalcopyrite(cp)-idaite(id)-nukundamite(nk) area of the Cu-Fe-S system; the solid solution is pronounced in the areas between id, bn and cp. The metastable phases of the solid solution are quenchable from above 500°C to 220°C; examples observed in natural assemblages form as a result of kinetic and energetic effects and as an accornmo-dation of the Gibbs/Goldschmidt phase rule. The occurrence of phases is constrained by hydrothermal phase equilibria. The states of the systems involve small compositional adjustments which are dependent on solid state processes. Mineral phases exhibit slight variations in stoichiometry allowing ties to exist between them. An accornmodation noted in nature allowing covellite(cv)-nk-cp colinearity is observed in experiments at 150-250°C where id compositions equilibrate so that the nk-cp tie connects. Transition metal (e.g., Zn) substitution occurs at low temperatures and chalcogenide (e.g., As) substitution occurs at high temperatures. Below 220°C (thermal maximum of non-stoichiometric chalcopyrite) and 260-270°C (where tie line switch reactions occur between id, cv and cp producing nk) the solid solution area becomes expansive widening toward cp; as a result of sympathetic energetic and kinetic effects a number of polytypes appear. The nk area remains restricted at high temperatures, variable stoichiometry and solid solution with id and an.bn polytypes is ob-served at, temperatures below 171-220°C. At high temperatures non integral superstructures decompose to integral types which are involved in tie-line switch reactions. Permissive metastability below 300°C is associated with merged univariant equilibria and sustained by non relativistic atomic states in superlattices which influence spectacular solubility variations. Lattice distortion and electronic states indicated for these phases suggest the presence of strong bonding forces, imposed by vacancy superstructure nuclear interactions, not specified by current theory.
Idaite exhibits 2 or 3 polytype and several polymorphous conditions; - 12 polytype phases are recognised in the an.cp solid solution between id and cp. Crystal symmetry varies from hexagonal (360°C: cubic) in nk, pseudocubic/tetragonal (220°C: cubic) in id to orthorhombic/tetragonal in an.cp; these symmetry transformations correlate with stoichiometry, metal vacancies and oxidation states (dependent on environment of crystallization hence the variety of natural polytypes). Changing levels of site occupation and oxidation state result in distortion of the basic chalcogenide subcell with concomitant superstructure and optical effects. A new concept of bond development is introduced to explain ob-served physical and chemical variations-chalcogenide ligands are thought to be metallized; especially notable in nonstoichiometric phases. Analogous chalcogenide phases from other systems are discussed in terms of their multielement phase equilibria and periodic element topology. A restructured periodic table facilitates a better understanding of zonal/regional metallogenesis and multielement solid state phase equilibria applicable to broad fields of scientific research. The occurrence of Au and tectonically zoned chalcogenides-semimetals (e.g., Ge anomalies at tectonic inflections) with zones intermediate Cu-Fe-S solid solution-metastable solid solution (iss-mss) series will provide an inter-est for mineral exploration and natural hazard monitoring.

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A field survey documented the lithostratigraphy and sampled for biostratigraphic, paleomagnetic and isotopic analyses of sedimentary sections to the east of Dannevirke, Southern Hawke's Bay, New Zealand. The studied marine sequence was deposited in the forearc basin along the Hikurangi Trench from the late Miocene to the latest Pliocene. The marine sequence is divided into Moastone, Mapiri, Mangatoro, Pukerua, Te Aute, Okarae, Kumeroa, and Mangatarata Formations in ascending order. The sedimentary sequence is cut into spindle shape blocks by faults with right lateral movements. Oxygen and carbon isotopes of foraminiferal tests indicate that the sedimentary environment was shallow, with relatively higher near-bottom than surface primary production. A distinct tec-tonic event occurred in the latest Pliocene, 2.2 Ma, reflected in an angular unconformity at the base of the Kumeroa Formation and deformation of the formation immediately after its deposition. The event rearranged the forearc basin and terminated the deposition within it. The event was associated with volcanic activity.

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Radiolarian faunas from several localities in the Matakaoa Volcanics of the Mangaroa Range, North Island, New Zealand indicate Late Cretaceous (Campanian to Maastrichtian) ages. This contrasts with Late Paleocene/Early Eocene ages obtained from foraminifera approximately 3 km higher in the section. The radiolarian faunas are cosmopolitan and may have been deposited at mid to high latitude.
A new structural analysis indicates that the fossils occur in a sequence of intercalated pillow lavas, sediments and dolerites about 10 km thick equivalent of layer 2B of the oceanic crust. This great thickness implies that there has been much repetition by shortening deformation. Layering dips steeply; younging is generally to the north and the sequence is affected by km-scale steeply plunging folds associated with decollements. Structural development involved first formation of melange, and subsequent refolding of these structures to give the present dextral, steeply plunging folds. It is not clear yet how another phase of deformation, steepening and overturning of layering in the Matakaoa Volcanics, relates to these two tectonic events.

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The Waitemata Group in the Upper Waitemata Harbour area is a turbidite sequence with interbedded volcaniclastic sandstones, rhyolitic granule-sand and tuff horizons, and conglomerate lenses containing metamorphic, volcanic, plutonic and sedimentary clasts. Clastic debris in the sediments is little altered except for devitrification of volcanic glass. Zeolites and clay minerals encrust clastic grains and fill pores. There is a strong lithologic control on diagenetic assemblages. Lithic-rich sandstones poor in volcanic debris have calcite cement. Volcaniclastic sandstones have zeolite cement with the paragenetic sequence clinoptilolite (+ mordenite) → chabazite and/or erionite, and finally rare analcime. Rhyolitic granule-sand horizons contain the paragenetic sequence analcime → clinoptilolite → chabazite and/or erionite. Conglomerate horizons, which frequently lack any vitric debris, have analcime cement. In rhyolitic tuff only mordenite occurs crystallising directly from devitrified glass shards. Clay minerals present are smectite and illite, and chlorite in highly altered volcaniclastic sediments. Interbedded mudstones sealed fluids into volcaniclastic sandstone and tuff horizons and diagenesis occurred in a closed hydrologic system. The original pore fluid, believed bicarbonate-rich, precipitated calcite cement in the absence of vitric debris. In volcaniclastic and vitric rocks devitrification of glass liberated alkalies and silica into pore fluids leading to crystallisation of zeolite. Conglomerates filling channels cut into other sediments were an open hydrologic system and analcime crystallised from Na-saturated fluids flowing through them.

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Silicified woods of probable Altonian (Lower Miocene) age occur in southeast Hukatere Peninsula, Kaipara Harbour, New Zealand. Pyroclastic flows, apparently flow-ing from a northerly direction, carried woods from a broadleaf-podocarp forest to mix with probable Avicennia (mangrove) growing in estuarine conditions close to the site of preservation. Many woods were partially or completely carbonized by the flow.
Thin section petrography, scanning electron microscope micrographs, and X-ray diffractograms indicate the woods were silicified by silica in solution, formed by devitrification of volcanic glass. The sequence of silicification is likely to have been either opal-A → opal-CT → α-quartz and chalcedony, or directly to α-quartz and chalcedony. The degree of crystallinity of the quartz is not time dependent. The mode of occurrence of α-quartz, chalcedony, cristobalite, tridymite, Iussatite and amorphous opal is described. Other minerals present in the woods include goethite and members of the saponite group, as well as organic compounds.

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Diagenesis of sediments derived from a magmatic arc provenance may greatly differ from that of sediments derived from an intracratonic- or foreland-type provenance. Sediments from the magmatic arc are compositionally immature and rich in volcanic and sedimentary rock fragments. Sandstone samples of mid- to Upper Cretaceous formations in the Queen Charlotte Islands, British Columbia, Canada, contain either large amounts of pseudomatrix or authigenic cements. An inverse relationship between the content of pseudomatrix and that of authigenic cements suggests that ductile deformation of soft rock fragments has reduced much of the original porosity and has preceded the formation of authigenic cement. The described inverse relationship clearly contradicts the recent report of diagenesis of sandstones rich in volcanic rock fragments (Hawlader 1990).

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Massive magnesite deposits in the Setogawa Group in Shizuoka were formed by an extensive carbonation of serpentinite in an ancient accretionary prism. Stable isotopic investigations of the origin of massive magnesite deposits revealed that a homogeneous deep-seated magmatic carbon mixing with marine limestones may be the main source of the carbon. Many calcite and dolomite veins occur in the serpentines, basaltic and pelitic rocks and based upon carbon and oxygen isotopes are supposed to be of similar origin to carbonate veins found in modern serpentine diapirs of the Izu-Bonin and Mariana is-land arc. In contrast, massive magnesite deposits were formed during the subduction of an active volcano and/or an active ridge, with circulation of magmatic carbon providing the carbon source for the serpentine diapirs.

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The Circum-Izu Massif Serpentine Belt is a fossil transcurrent plate boundary of the Oligocene-Miocene time beween the Philippine Sea and the Eurasia plates. The Circum-Izu Massif Serpentine Belt encircles the northern end of the Izu Massif, almost parallel to a trace of the present plate boundary, the Sagami Trough and the Suruga Trough. The Circum-Izu Massif serpentinite had been mainly emplaced into or protruded onto the Oligocene-Miocene sediments. The Circum-Izu Massif peridotite, mainly harzburgite, is characterized by the mineral assemblage, olivine (Fo₉₀₋₉₂) + opx + cpx + chromian spinel (Cr#, ca. 0.5) +/− plagioclase (An₉₀), and is a low-pressure (ca. 5 kb) restite with or without melt impregnation. It may represent the uppermost mantle of the Shikoku Basin, which had begun opening during Oligo-Miocene, protruded along the transcurrent plate boundary at the northern end of the Philippine Sea plate (the Shikoku Basin), by analogy with the protrusion of abyssal peridotites along the oceanic fracture zone. It had been accreted to the Eurasia plate by the ocean-ward bending of the central Honshu arc during the opening of the Sea of Japan in the Miocene. Detrital chromian spinel grains in the Oligocene-Miocene sediments in the Circum-Izu Massif Serpentine Belt memorize some ancestral peridotites with arc-mantle characteristics which had been protruded in the Belt before the present Circum-Izu Massif serpentinite (peridotite). The ancestral peridotites and dioritic rocks frequently associated with the sepentinites were derived from the deep parts of the Paleo-Izu-Bonin arc, which had been split and disrupted by the Shikoku Basin opening. Picritic basalts of intra-plate type closely associated with the Circum-Izu Massif serpentinite were possibly derived from the mantle plume which had caused the opening.

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This district is located on the southwest of Mt. Fuji, the south part of the Fossa Magna area.
The Agoyama active fault extends from north to south, between a hill named Habuna and the skirt of Mt. Fuji. Another active fault so-called Ohmiya fault, runs from NW to SE, between a hill of Hoshiyama and the Mt. Fuji. The Fujikawa Fault trend-ing north to south, traverse the eastend of the later hill, extends to the Suruga Trough.
All these faults are concealed with volcanic ash, so that these fault lines are not accurately known. Therefore, in order to discriminate these faults, linear features have been delineated, using Landsat images and stereo airphotos.
Successively, γ-ray dose rates have been measured along the lines across these faults to confirm the precise position of the faults. γ-ray dose rates obtained on the points of these faults seem to show rather higher figures than those of other points.

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