Hidaka Metamorphic Belt Research Articles

Structural evolution of the Horoman peridotite complex in conjunction with the formation of the Hidaka Metamorphic Belt, Hokkaido

We conducted crystal-fabric analyses of peridotites within the Horoman peridotite complex in the Hidaka metamorphic belt, Hokkaido, Japan. Over fifty oriented peridotite samples were collected and analyzed for olivine fabric strength (J-index) and crystallographic preferred orientations (CPOs). The peridotites contained four olivine CPOs: A, E, D, and AG types. We confirmed that olivine CPOs presented a transitional distribution from E to A to AG type from south to north. Previous experimental studies have demonstrated that E type CPO can merge under hydrous conditions. In addition, magnetotelluric observations suggested that the subducting oceanic plate supplies pore fluid to the basal thrust in the region (the Hidaka Main Thrust). Therefore, we infer that the E type CPO was originated from a local water infiltration event. AG type CPO, on the other hand, was considered as a secondary product enhanced by the heating event in the northern (geological upper) part, combined with the pressure-temperature path inferred by previous petrological studies. Furthermore, we reconstructed the senses of shear strain using the microstructure and olivine crystal-fabrics. Then we built the tectonic history of the Horoman peridotite complex integrating the structural development of the Hidaka Metamorphic Belt.

Hydration of mafic crustal rocks at high temperature during brittle‐viscous deformation along a strike‐slip plate boundary

AbstractThe Poroshiri ophiolite (Hidaka metamorphic belt, Japan) occurs within a crustal‐scale network of high‐temperature, dextral shear zones that accommodated hundreds of kilometres of displacement due to the opening of the Japan Sea in the Neogene. The opholitic rocks comprise ultramafic, mafic and sedimentary protoliths that have been variably hydrated and metamorphosed. This work investigates the mechanisms and timing of fluid influx relative to viscous deformation in metagabbros and amphibolites deformed during exhumation from granulite‐ to amphibolite‐facies conditions. We consider a range of microstructures, from low strain domains and 1–2 mm thick shear bands to mylonites with a thickness of a few meters. Low strain domains of metagabbros exhibit corona textures with symplectites consisting of pargasitic amphibole (Ed0.7) ‐ anorthitic plagioclase (An80–92) ± orthopyroxene ± clinopyroxene forming around olivine and igneous pyroxene and with similar plagioclase–amphibole‐orthopyroxene ± clinopyroxene granoblastic aggregates in micrometric‐thick fractures. These textures result from hydration under low fluid‐rock ratio, with elevated H2O content only occurring locally (H2O > 1–1.2 wt%). Igneous mineral replacement leads to grain size reduction from 1 mm to ~10 μm. Amphibole exhibits a strong core‐rim zonation primarily controlled by the high diffusivity of Fe, Mg and OH and the low diffusivity of Al. Mineral compositional equilibrium is achieved at the scale of 100–200 μm. In mm‐thick localized shear bands and in metric‐scale mylonitic amphibolites, the heterogeneous mineral composition of amphibole (Ed0.2–0.5) and plagioclase (An40−An80) indicates only partial re‐equilibration (at the scale of 200–500 μm) despite higher fluid‐rock ratios and more pervasive fluid percolation than in metagabbros. Plagioclase–amphibole thermometry and equilibrium phase diagrams indicate that the initial fluid infiltration and corona formation occurred at 800–850°C by fracturing and percolation along grain boundaries. This was followed by the main fluid percolation and mylonitization event, which occurred during exhumation and cooling at conditions of 720–580°C, ~4 kbar. Continuous hydration during retrogression was achieved by the influx of dominantly seawater‐derived fluid, as attested by the high chlorine (Cl) contents (>300–400 ppm) of amphiboles in fractures. The heterogeneous distribution of fractures controls the distribution of fluid from the earliest stages of hydration, creating positive feedback where the growth of hydrous minerals as amphibole (up to +300 vol% of amphibole in high strain areas relative to the low‐strain ones) and the formation of fine‐grained mixed domains that led to further localization of viscous strain and mass transfer (variations of ± 30–40% in major elements). The Poroshiri ophiolite therefore represents a good fossil example of a former transpressional plate boundary where coupled metamorphic and deformation processes were triggered by seawater‐derived fluid that percolated to depths of ~15 km.

Variation in olivine crystal-fabrics and their seismic anisotropies in the Horoman Peridotite Complex, Hokkaido, Japan

We examined the microstructures and crystal-fabrics of peridotites within a large area (6×5km) of the Horoman Peridotite Complex in the Hidaka metamorphic belt of Hokkaido, Japan. Thirteen peridotite samples were analyzed for olivine and orthopyroxene grain sizes, fabric strength (J-index), and crystallographic preferred orientations (CPOs). Mean grain sizes of olivine and orthopyroxene were ranged in 295–497µm and in 257–537µm, respectively. The olivine fabric strength values decreased from the lower to the upper part of the complex, whereas the orthopyroxene fabric strength values showed no systematic trends. The peridotites contained three different olivine CPOs, previously known as A, E, and AG types. Combined with a previous study, we found that olivine CPOs showed a transitional distribution from E to A to AG type from south to north. E type peridotites occur at the basement of the complex in the south, suggesting that local water infiltration might occur at the basement of the complex. The A type peridotites occurred mainly in the middle of the studied area and subsequently the AG type peridotites occurred towards the north. Moreover, we calculated the seismic properties of peridotite as olivine 100% aggregates and mixed (olivine and orthopyroxene) aggregates. It showed that orthopyroxene CPOs reduce P-wave anisotropies of peridotite (0.2–2.2%) without modification of the P-wave propagation patterns.

Timing of Izanagi-Pacific ridge subduction beneath Eurasia: Constraints from metamorphic soles in Hokkaido, Japan

The subduction of the Pacific Plate beneath Eurasia controls not only Cenozoic intraplate volcanism, but also deep-focus earthquakes along the continental margin of eastern Asia. However, the timing of subduction of the Paleo-Pacific (Izanagi)−Pacific ridge and the initial subduction of the Pacific Plate beneath Eurasia remain subjects of debate. Metamorphic soles provide key evidence for ridge subduction, and together with coeval igneous activity, they are widely used to constrain the timing of ridge subduction. Here, we present the results of a study of amphibolites from the Hidaka metamorphic belt, Hokkaido, northern Japan, which are interpreted to be metamorphic soles. Our integrated study involved secondary ion mass spectrometry (SIMS) U-Pb zircon dating, mineral chemistry, whole-rock geochemistry, and Sr-Nd-Pb-Hf isotopic analyses. SIMS U-Pb zircon dating indicates that the amphibolite-facies sole metamorphism occurred in the late Eocene. Phase equilibria modeling suggests that the peak P−T conditions of metamorphism were 8.0−9.5 kbar/700−730 °C. The amphibolites belong to the tholeiitic series, and they are relatively enriched in heavy rare earth elements relative to light rare earth elements, with depletions in Nb, Ta, P, and Ti. They have (87Sr/86Sr)i = 0.704207−0.704998, εNd(t) = +11.65 to +11.96, εHf(t) = +14.28 to +16.32, (206Pb/204Pb)i = 18.240−18.255, and (207Pb/204Pb)i = 15.522−15.525. The geochemistry of these amphibolites reveals that their protoliths had normal mid-oceanic-ridge basalt affinities, and their Pb isotopic signatures indicate Indian-type mantle rather than Pacific-type mantle. Considering the geochemistry of coeval igneous rocks, we conclude that the late Eocene metamorphism in the Hidaka metamorphic belt records the intraoceanic subduction that followed heat transfer from the incipient mantle wedge toward the top of the subducting plate, and it provides a key constraint on the timing of subduction of the Izanagi-Pacific ridge.

Repeated metamorphism in the pelitic granulites of the Hidaka metamorphic belt, Hokkaido, Japan: Implications for the formation of the present‐day trench‐arc‐basin system in NE Asia

AbstractThe timing and mechanism of the tectonic transition from an active continental margin to a trench‐arc‐basin system in NE Asia are debated. In this study, we report the pressure–temperature–time (P–T–t) path of this transition based on petrographic observations, phase‐equilibrium modelling, and U–Pb ages of zircon and rutile from pelitic granulites in the Hidaka metamorphic belt (Hokkaido, Japan). The granulites contain an early phase mineral assemblage of staurolite + sillimanite + biotite + plagioclase + quartz + rutile/ilmenite, a peak phase granulite assemblage of garnet + biotite + cordierite + plagioclase + quartz + rutile/ilmenite and a symplectic intergrowth of spinel + cordierite ± sillimanite within garnet porphyroblasts. Phase‐equilibrium modelling indicates two phases of metamorphism with P–T conditions, respectively, of ~6 kbar/620–670°C and ~6 kbar/850°C. A clockwise P–T path was thus reconstructed for the granulites, showing a near‐isobaric temperature increase to the peak conditions and a post‐peak cooling. U–Pb dating of zircon and rutile in the granulites yielded two groupings of metamorphic ages at c. 37 Ma and 19 Ma, related to early phase amphibolite facies and late phase granulite facies metamorphism, respectively. The age of magmatism from the previous work at the NE Asian continental margin overlaps with these metamorphic ages, and the two phases of metamorphism in the pelitic granulites is attributed to discrete episodes of supra‐subduction‐zone magmatism (late Eocene, c. 37 Ma) and back‐arc extension (early Miocene, 24–19 Ma). Consequently, we suggest that the Hidaka metamorphic belt has undergone two phases of metamorphism, which represent two pulsed and separated thermal events. Moreover, we relate the granulites facies metamorphism to the underplating of mafic magma and lithospheric thinning during the opening of the Japan Sea at 24–19 Ma, which is attributed to slab rollback and trench retreat processes in NE Asia.

Remarkably fresh abyssal peridotites from Sibuyan island, Romblon Island Group, Philippines: Markers of young arc-continent collision

The bulk of Sibuyan island in the Romblon Island Group, Philippines is underlain by remarkably fresh spinel lherzolites, harzburgites and dunites collectively called as the Sibuyan Ultramafics. Based on petrographic and geochemical characteristics, the Sibuyan Ultramafics can be classified into: (1) Group I peridotites composed of spinel lherzolites and harzburgites with spinel Cr# < 0.35, (2) Group II harzburgites and dunites with intermediate spinel Cr# = 0.40–0.65, and (3) Group III dunites with very high spinel Cr# (>0.75). Increase in spinel Cr# is accompanied by decreasing Al2O3 contents and increasing Mg# in the pyroxenes from the Group I to Group II and Group III peridotites. Chondrite-normalized clinopyroxene data revealed various trace-element patterns for the three groups suggestive of different processes (e.g. anhydrous and hydrous melting, mantle-melt interaction) involved in their formation. The Sibuyan Ultramafics is closely associated with the similarly fresh Calaton Hill metamorphic/plutonic complex in Tablas island which is thought to be representative of the lower crust of the Philippine island arc. At a more regional context, the Sibuyan Ultramafics and the Calaton Hill metamorphic/plutonic complex can be used as markers for the young arc-continent collision in western Philippines. Rapid uplift and emplacement due to the collision of the Philippine Mobile Belt and the Palawan Microcontinental Block during the Miocene or even later may have led to the remarkably fresh state of these lithologies. This occurrence is similar to the Horoman peridotite complex in the Hidaka metamorphic belt in Northern Japan. The Sibuyan Ultramafics and the Calaton Hill metamorphic/plutonic complex therefore provide a rare and fresh glimpse into the upper mantle and lower crust in the Philippines due to their young ages of emplacement.

U–Pb ages of zircons from metamorphic rocks in the upper sequence of the Hidaka Metamorphic Belt, Hokkaido, Japan: Identification of two metamorphic events and implications for regional tectonics

AbstractThe Hidaka Metamorphic Belt is a well‐known example of island‐arc crustal section, in which metamorphic grade increases westwards from unmetamorphosed sediment up to granulite facies. It is divided into lower (granulite to amphibolite facies) and upper (amphibolite to greenschist facies) metamorphic sequences. The metamorphic age of the belt was considered to be ~55 Ma, based on Rb–Sr whole‐rock isochron ages for granulites and related S‐type tonalities. However, zircons from the granulites in the lower sequence yield U–Pb ages of ~21–19 Ma, and a preliminary report on zircons from pelitic gneiss in the upper sequence gives a U–Pb age of ~40 Ma. In this paper we provide new zircon U–Pb ages from two pelitic gneisses in the upper sequence to assess the metamorphic age and also the maximum depositional age of the sedimentary protolith. The weighted mean 206Pb/238U ages from a biotite gneiss in the central area of the belt yield 39.6 ± 0.9 Ma for newly grown metamorphic rims and 53.1 ± 0.9 Ma for the youngest detrital cores. The ages of zircons from a cordierite–biotite gneiss in the southern area are 35.9 ± 0.7 Ma for metamorphic rims and 46.5 ± 2.8 Ma for the youngest detrital cores. These results indicate that metamorphism of the upper sequence took place at ~40–36 Ma, and that the sedimentary protolith was deposited after ~53–47 Ma. These metamorphic ages are consistent with the reported ages of ~37–36 Ma plutonic rocks in the upper sequence, but contrast with the ~21–19 Ma ages of metamorphic and plutonic rocks in the lower sequence. Therefore, we conclude that the upper and lower metamorphic sequences developed independently but coupled with each other before ~19 Ma as a result of dextral reverse tectonic movement.

Pressure dependence of graphitization: implications for rapid recrystallization of carbonaceous material in a subduction zone

We report the results of kinetic experiments of graphitization at various pressures (0.5–8.0 GPa) and durations (1 s to 24 h) at 1200 °C. The natural carbonaceous material in sedimentary rocks from the Shimanto accretionary complex and the Hidaka metamorphic belt, Japan, underwent systematic changes in crystallinity and morphology with increasing pressure. To assess the pressure dependence of graphitization, we adopted three approaches to formulating the graphitization kinetics using a power law rate model, a Johnson–Mehl–Avrami–Kolmogorov model, and a superposition method. Activation volumes of − 21.7 ± 3.0 to − 45.7 ± 4.5 cm3 mol−1 and − 0.7 ± 0.2 to − 16.8 ± 1.8 cm3 mol−1 were obtained for pressures from 0.5 to 2.0 GPa and 2.0 to 8.0 GPa, respectively. Such large negative activation volumes might arise from structural modification and compression in the primary carbonaceous material. We applied the experimental data to the Arrhenius-type equation of graphitization, extrapolated to geological P–T–t conditions. Our model predicts that carbonaceous material undergoing metamorphism for ~ 10 Myr at pressures of 0.5–3.0 GPa will begin to crystallize at around 350–420 °C and transform fully to ordered graphite at around 450–600 °C, depending on the peak pressure. Thus, natural graphitization might proceed much more rapidly than previously estimated, owing to the large negative activation volumes for the reaction rate. This indicates that subducted carbonaceous materials will completely convert to fully ordered graphite by rapid recrystallization and metamorphic devolatilization before reaching sub-arc depths (< 100 km).

Petrological features of olivine-norite along the Ougon-douro, southern part of the Hidaka metamorphic belt, Hokkaido

Petrological features of olivine-norite along the Ougon-douro, southern part of the Hidaka metamorphic belt, Hokkaido

Microstructure and geochemical signatures of metasedimentary origin pseudotachylyte: Implications for fluid activity during paleoseismicity

The redox state of pseudotachylyte provides valuable information on the physicochemical properties related to fluid activity during paleoseismicity. In this study, we evaluate the behavior of fluids in pseudotachylytes using fluid buffering minerals such as graphite and other secondary minerals. Two types of pseudotachylyte were identified in the Hidaka metamorphic belt, Hokkaido, Japan; Pst I and Pst II. Pst I is composed of pyrrhotite and K-feldspar generated by the breakdown of phyllosilicates, whereas Pst II includes recrystallized biotite microlites, K-feldspar, and plagioclase due to the breakdown of quartz and feldspars, as well as phyllosilicates. The selective frictional melting of phyllosilicates is indicated by significant changes in the concentrations of large ion lithophile elements (e.g., Ba, Sr, Rb, Cs, B, and K). In addition, the graphite associated with titanite and hydroxyapatite is often distributed within the Pst II matrix. The graphite exhibits different crystallinity, morphology, and higher carbon stable isotopic compositions (δ13C = −21.9 ± 2.3‰, n = 16), when compared with metamorphic graphite extracted from the protolith (δ13C = −25.1 ± 0.8‰, n = 15), cataclasite, ultracataclasite, and Pst I (δ13C = −25.2 ± 0.8‰, n = 15). The microstructure and geochemical signatures in both pseudotachylytes are controlled by dehydration–redox reaction of phyllosilicates coexisting with sulfide minerals and graphite. In particular, the formation of 13C enriched graphite in the Pst II can be deduced by co-precipitation of fluid-deposited graphite with hydrous minerals from H2O-CH4 fluids and/or degassing of H2O-CH4 fluids from residual graphite. Our data demonstrated that the carbonic fluids of a reducing nature could be produced, and then dissolved into the pseudotachylyte melt by frictional melting of metasedimentary rocks. The production of carbonic fluids by coseismic slip may be an overlooked process in the remobilization of refractory graphite locked in the crust.

Plutonic and metamorphic rocks in the southern Hidaka metamorphic belt, Hokkaido

Plutonic and metamorphic rocks in the southern Hidaka metamorphic belt, Hokkaido

日高変成帯西帯,幌尻岩体の角閃石( 造岩鉱物研究の現状と展望-地団研第33回総会鉱物学ミニシンポジウム-)

日高変成帯西帯,幌尻岩体の角閃石( 造岩鉱物研究の現状と展望-地団研第33回総会鉱物学ミニシンポジウム-)

An experimental kinetic study on the structural evolution of natural carbonaceous material to graphite

We report here new experimental kinetic data on the structural evolution of carbonaceous material (CM) to graphite during heating at various temperatures (1000 to 1450 °C) for various durations (10 min to 115 h) under a pressure of 1 GPa. Natural CMs extracted from sedimentary rocks in the Shimanto accretionary complex and the Hidaka metamorphic belt of Japan transformed in morphology and crystallinity with increasing temperature and annealing duration to become fully ordered graphite ( d 002 spacing ~3.36 A). Transmission electron microscopy showed that both samples have undergone microstructural evolution from amorphous carbon to platy graphitic carbon. These changes match the evolution of the samples’ X-ray diffraction (XRD) patterns and micro-Raman spectra. The time–temperature relations of crystal parameters obtained by XRD and micro-Raman spectroscopy demonstrated a sigmoidal transformation curve from an amorphous to a graphitic structure, suggesting complexity of these successive and/or parallel chemical reactions are responsible for graphitization. To assess these complex chemical processes, we adopted three different approaches for formulating the graphitization kinetics using a power rate model, a Johnson-Mehl-Avrami (JMA) model and a superposition method. Irrespective of the models employed, the effective activation energies were estimated to lie between 259 and 339 kJ/mol, which are much lower than those reported previously for graphitization. Summarizing the previous studies and our results between 0.1 and 1000 MPa, we found that the effective activation energies systematically decrease as a function of pressure. Based on the experimental results in this study, the sigmoid functions obtained from the time–temperature relations can be extrapolated to low-temperature conditions at 1 GPa. Our kinetic model using unit-cell height c predicts that CM undergoing metamorphism for about 1 m.y. will begin to crystallize at ~410 °C, and will transform to fully ordered graphite at over ~520 °C. Thus, natural graphitization undergoes a much faster transformation than reported in previous studies at 1 atm and could be explored in laboratory experiments using natural precursor materials under pressure conditions and time spans that reflect natural conditions in the Earth’s crust.

Heat transportation mechanism in the Hidaka Metamorphic Belt

Heat transportation mechanism in the Hidaka Metamorphic Belt

Evolution of the Hidaka Metamorphic Belt, part I: Dual metamorphism and duplicate crust

Evolution of the Hidaka Metamorphic Belt, part I: Dual metamorphism and duplicate crust

Partial melting of mafic metamorphic rock in the Main Zone of the Hidaka metamorphic belt in Hokkaido

Partial melting of mafic metamorphic rock in the Main Zone of the Hidaka metamorphic belt in Hokkaido

Crustal composition in the Hidaka Metamorphic Belt estimated from seismic velocity by laboratory measurements

Crustal composition in the Hidaka Metamorphic Belt estimated from seismic velocity by laboratory measurements

Estimation of rock composition of crust based on measurements of elastic wave velocities: a case study of the Hidaka Metamorphic Belt

Estimation of rock composition of crust based on measurements of elastic wave velocities: a case study of the Hidaka Metamorphic Belt

Structural geology of metamorphic rocks and tonalites from the Kamiutabetu-gawa area in the southernmost part of the Hidaka Metamorphic Belt, Hokkaido, japan

Structural geology of metamorphic rocks and tonalites from the Kamiutabetu-gawa area in the southernmost part of the Hidaka Metamorphic Belt, Hokkaido, japan

Origin of the I- and S-type tonalite magma in the Satsunai-gawa Shichino-sawa river region of the Hidaka metamorphic belt, Hokkaido, northern Japan: Inferences from Sr and Nd isotopic compositions

日高変成帯中部地域に分布する37 MaのIタイプとSタイプトーナル岩のSrとNdの同位体比組成から，トーナル岩類の成因を検討した．Iタイプの角閃石黒雲母トーナル岩は砂泥質変成岩類に貫入し，その周囲にSタイプの白雲母黒雲母トーナル岩を形成している．その同位体比組成変化は壁岩の砂泥質岩との同化分別結晶作用に起因する．また，NdIは変成帯下部層の苦鉄質変成岩類と一致しない．このことから，角閃石黒雲母トーナル岩マグマの起源物質は苦鉄質変成岩類ではない．その候補となるのは，音調津地域のノーライトを形成した苦鉄質マグマと同等の物質であろう．