Rocks In Japan Research Articles

Separation of Phosphorus from Phosphorus-concentrated Steelmaking Slag

Since 10 million tons of steelmaking slag, which contains a few percent of phosphorus, are annually produced, the phosphorus amount in the slag is equivalent to the annual import volume of phosphorus rock in Japan. Therefore, the steelmaking slag is attracting attention as a potential phosphorus resources. Phosphorus-concentrated slag obtained by the dephosphorization reaction between high phosphorus hot metal and oxidizing slag at high temperature contains phosphorous comparable to that of phosphorus rock. However, because of high FeO concentration, it is difficult to use for phosphorus resources directly. In this work, the effects of pH, acid type and leaching method on the dissolution behavior of phosphorus from P-concentrated slag were investigated. As a result, phosphorus dissolution progressed at lower pH, and was promoted by the addition of citric acid, which is known as a chelate former. When nylon mill pot stirring with citric acid and alumina mill pot stirring with nitric acid were compared to impeller stirring, respectively. By combining nylon mill pot stirring and citrate leachate, phosphorus dissolution was accelerated, because the slag was pulverized during stirring and a formation of insoluble metal-phosphate was inhibited by the formation of complex ion between leached metal cation and citrate. When the slag was leached with alumina mill pot while controlling pH by nitric acid, the phosphorus dissolution ratio lowered since phosphorus ion and aluminum ion, which is supplied by the dissolution of pot and crushing ball during leaching, constructed secondary products with low solubility along with other dissolved ions.

Octocorals (Alcyonacea and Pennatulacea) from Paleogene deep-water strata in western Washington State, USA

AbstractThe fossil record of octocorals from Cenozoic marine strata of western North America is quite limited, and they have not been reported previously from rocks in Washington State, USA. Two late Oligocene specimens from the upper part of the Lincoln Creek Formation in western Washington, referred to Radicipes? sp., are the first fossil record of the family Chrysogorgiidae. The family Isididae is represented by an internode and two holdfasts identified as Isidella sp. collected from the Oligocene Pysht Formation, along with specimens questionably identified as Lepidisis sp., possibly the first fossil record for this genus. Together, these are the first confirmed fossils of the Alcyonacea from north of California in western North America. The axes of sea pens from several late Eocene or early Oligocene localities in the Lincoln Creek Formation in the central part of western Washington, and the Pysht and Makah formations on the north side of the Olympic Peninsula, are the first fossil record for the Pennatulacea from western North America; all are tentatively referred to the genus ‘Graphularia’. Large axes from the Lincoln Creek Formation and Makah Formation are referred to ‘Graphularia’ (?) aff. sasai, because they are similar to the species known only from late Eocene and early Oligocene rocks in Japan.

Physical properties of Neogene granitic rocks in Japan

Physical properties of Neogene granitic rocks in Japan

Tight oil exploration in the Onnagawa formation, Miocene biosiliceous rocks of Japan: what we have learned and its implication for Monterey-like siliceous rocks in the Circum-North Pacific

We re-discovered tight/shale oil accumulations through a successful acid treatment in the Onnagawa Formation, the main petroleum source rock in Japan, which is Monterey-like biosiliceous shale of the Middle Miocene age. Its productivity is fairly high, comparable with that of the Bakken shale, and is supported by matrix pores of quartz-porcelanite and carbonate-cemented natural fractures which is stimulated effectively through acidizing. The tight oil horizon corresponds to the best source and the best reservoir rocks. It is the most siliceous part of the formation, which is reasonably understood as a result of an increase in primary productivity with diatom blooms in the Miocene age. We think the tight oil is generated in situ and a part of continuous accumulation, while it is in a structural trap so far. The above exploration concept will be applicable to the Monterey Formation of California and the Dae-Khurie Formation of Sakhalin, which are siliceous rocks of same type, and re-evaluation of non-commercial hydrocarbon flows or shows in exploratory wells is recommended.

Reappraisal of the oldest high-pressure type schist in Japan: New zircon U-Pb age of the Kitomyo Schist of the Kurosegawa Belt

The Kitomyo Schist from Kurosegawa Belt, Shikoku, has been long considered as the oldest records of subduction metamorphism in Japan, based on an early 1970s K–Ar dating of white mica. The schist consists of mafic and pelitic layers and occurs as a tectonic block within serpentinite. Reappraisal of the schist confirmed the schist is characterized by an epidote-amphibolite peak metamorphic facies. The mafic portion is characterized by zoned amphibole + epidote + chlorite + titanite ± phengite ± rutile. The presences of relict rutile surrounded by titanite and the barroisitic cores of zoned amphibole suggest a high-pressure intermediate type metamorphism at the metamorphic peak (P = ~0.8–1.5 GPa and T = ~500–570 °C). The presence of Mn-rich garnet and the lack of biotite, oligoclase and paragonite also support high-pressure intermediate type metamorphism that eliminate the possibility of a typical blueschist-facies metamorphism. New SHRIMP and LA-ICPMS zircon U–Pb geochronology on a pelitic sample show detrital grains of Mesoproterozoic and Early Paleozoic ages, suggesting a maximum deposition age for the trench-fill sediment of ~440 Ma. Also the U–Pb data confirmed ~360 Ma overgrown rims that might have formed during the subduction zone epidote-amphibolite facies metamorphism. Reappraisal revealed that the Kitomyo Schist is not the oldest high-pressure type schist in Japan and rather comparable to the Late Paleozoic Renge Metamorphic Rocks and their equivalents in the Kurosegawa Belt. The Devono–Carboniferous high-pressure metamorphic rocks in Japan might have been paired with their coeval batholiths along the ‘Greater South China’ margin that was extensively eroded during later tectonic processes.

Direct mineralization of atmospheric CO2 using natural rocks in Japan

Gas-solid mineralization of atmospheric CO2 using naturally abundant surface rocks under ambient conditions and without thermochemical treatment was analyzed for application in Japan. Based on an empirically-verified theoretical framework, a tiered greenhouse containing finely ground rocks was designed with low-speed induced airflow to realize CO2 mineralization reactions over 1 year. Negative CO2 emissions were calculated accounting for CO2 emissions from energy generation, materials production, and removal of vegetation and soil. Under practicable operating conditions, negative emissions using crystalline surface rocks in Japan can reach ∼7.6 Gt-CO2/y achieved across 726 sites. The average energy requirement was calculated to be 1.5 GJ t−1-CO2 with an average land requirement of 1.1 km2 per Mt-CO2 annual removal capacity. Carbon debt is paid off after 60 d of operation.

The turnover of continental planktonic diatoms near the middle/late Miocene boundary and their Cenozoic evolution.

Fossil evidence indicates that modern assemblages of temperate nonmarine planktonic diatoms began near the middle/late Miocene boundary when the genus Actinocyclus, an important constituent of lacustrine planktonic diatom assemblages during the early to middle Miocene, was replaced by genera of the family Stephanodiscaceae. This floral turnover has been confirmed in many regions of the world, except eastern Asia where taxonomic data about early and middle Miocene planktonic diatom assemblages have until recently been scarce. Our analysis of Lower and Middle Miocene lacustrine diatomaceous rocks in Japan confirms that species of nonmarine Actinocyclus were important constituents of lake phytoplankton there as well. The appearance of nonmarine Actinocyclus species near the beginning of the Miocene may have resulted from the introduction of euryhaline species into lacustrine environments during a highstand of sea level at that time. Similarly, it is possible that species of Stephanodiscaceae evolved from marine thalassiosiroid ancestors that invaded high latitude lacustrine environments during multiple Paleogene highstands, resulting in a polyphyletic origin of the family. The turnover from nonmarine Actinocyclus to Stephanodiscaceae genera near the middle/late Miocene boundary may be linked to a contemporaneous increase in silica concentrations in lakes caused by active volcanism, increased weathering of silicate rocks due to orogeny, and the expansion of C4 grasslands. This turnover may also have been influenced by enhanced seasonal environmental changes in the euphotic zone caused by the initiation of monsoon conditions and a worldwide increase in meridional temperature gradients during the late Miocene. Morphological characteristics of Stephanodiscaceae genera, such as strutted processes and small size, suggest their species were better adapted to seasonal environmental changes than nonmarine species of Actinocyclus because of their superiority in floating and drifting capabilities and possibly metabolism, intrinsic growth rate, and reproductivity. As climates deteriorated during the late Miocene, Stephanodiscaceae species may have spread from high latitudes to temperate lakes where they diversified, ultimately displacing Actinocyclus.

Role of Potassic Alteration for Porphyry Cu Mineralization: Implication for the Absence of Porphyry Cu Deposits in Japan

AbstractThe role of potassic alteration and associated quartz veins for porphyry Cu mineralization in two representative porphyry systems (El Salvador, Chile, and Grasberg, Indonesia) was examined to evaluate the potential of porphyry Cu mineralization in Japan. The reactions between the aqueous magmatic–hydrothermal fluids and host rocks during potassic alteration at El Salvador and Grasberg includes (i) reduction of SO42− in the aqueous fluids due to oxidation of ferrous iron in mafic minerals and (ii) disproportionation of SO2 in the fluids by elevated concentrations of Ca2+ leached by the fluids from igneous plagioclase and hornblende. These reactions resulted in an increase of reduced S species (H2S) in the fluids and promoted Cu sulfide precipitation during the potassic or subsequent chlorite–sericite alteration in the temperature range of 600–400°C.Although numerous magnetite‐series, calc‐alkaline intrusive stocks of dioritic or granodioritic composition are exposed in the Sanin belt of the Cretaceous–Paleogene Southwestern Japan arc and late Miocene Northeast Japan arc, potassic alteration represented by abundant hydrothermal biotite, magnetite, and K‐feldspar is uncommon in these rocks. However, the intrusive rocks may have undergone molybdenite mineralization in association with phyllic alteration, represented by quartz, sericite and pyrite, or chalcopyrite in chlorite–sericite alteration in the subepithermal and epithermal environments at <400°C. The absence of porphyry Cu deposits in the Japanese islands in petrochemically and compositionally favorable intrusive rocks is ascribed to the lack of early quartz veins and poor development of potassic alteration that prevented Cu sulfide precipitation at high temperatures. The lack of early quartz veins and scarcity of potassic‐altered intrusive rocks in Japan is explained by the noncompressional stress field throughout the Japanese islands, which was incapable of maintaining lithostatic pressures during fluid exsolution from the intrusive magmas.

Measurements of radon exhalation rate in NORM used as consumer products in Japan

Twenty-five beauty products known to contain natural radionuclides were collected, and their 222Rn mass exhalation rates were measured. The effective doses to workers due to 222Rn exhaled from these products were estimated. The 222Rn mass exhalation rates of these products were below 177 μBq kg−1 s−1 and were almost identical to those of natural rocks in Japan. The maximum effective dose of 222Rn exhaled from these products was 71 μSv y−1.

Renewed profile of the Mesozoic magmatism in Korean Peninsula: Regional correlation and broader implication for cratonic destruction in the North China Craton

Jurassic-Cretaceous magmatic rocks in Japan, KP, and NE China-North China indicate that the subduction of the Paleo-Pacific plate might not be operative before Late Cretaceous (~130–120 Ma). (5) Late Cretaceous magmatic rocks (~90–60 Ma) occur in the southwestern corner of the KP and also in Japan, coinciding with the metamorphic age of ~90–70 Ma in the Sanbagawa metamorphic belt of Japan. The magmatic-metamorphic rock associations and their spatial distribution demonstrate the affinities of sequentially subduction zone, island arc and back-arc basin from Japan to Korea, arguing for the Pacific plate subduction during Late Cretaceous. (6) This study raises another possibility that the Mesozoic cratonic destruction in the NCC, which mainly occurred during ~150–120 Ma, might not only be due to the subduction of the Paleo-Pacific Plate, but also owe much to the intraplate geodynamic forces triggered by other adjacent continental plates like the Eurasian and Indian plates. Abstract Widespread Mesozoic magmatism occurs in the Korean Peninsula (KP). The status quo is poles apart between the northern and southern parts in characterizing its distribution and nature, with the nearly absence of any related information in North Korea. We have the opportunity to have conducted geological investigations in North Korea and South Korea during the past ten years through international cooperation programs. This led to the revelation of a number of granitoids and related volcanic rocks and thus facilitates the comparison with those in East China and Japan. Mesozoic granitoids in the KP can be divisible into three age groups: the Triassic group with a peak age of ~220 Ma, the Jurassic one of ~190–170 Ma and the late Early Cretaceous one of ~110 Ma. The Triassic intrusions include syenite, calc-alkaline to alkaline granite and minor kimberlite in the Pyeongnam Basin of North Korea. They have been considered to form in post-orogenic settings related to the Central Asian Orogenic Belt (CAOB) or the Dabie-Sulu Orogenic Belt (DSOB). The Jurassic granitoids constitute extensive occurrence in the KP and are termed as the Daebo-period magmatism. They correlate well with coeval counterparts in NE China encompassing the northeastern part of the North China Craton (NCC) and the eastern segment of the CAOB. They commonly consist of biotite or two-mica granites and granodiorites, with some containing small dark diorite enclaves. On one hand, Early Jurassic to early Middle Jurassic magmatic rocks are rare in most areas of the NCC, whilst Middle-Late Jurassic ones are not developed in the KP. On the other hand, both NCC and KP host abundant Cretaceous granites. However, the present data revealed contrasting age peaks, with ~130–125 Ma in the NCC and ~110–105 Ma in the KP. Cretaceous granites in the KP comprise the dominant biotite granites and a few amphibole granites. The former exhibit mildly fractionated REE patterns and zircon e Hf( t ) values from - 15 to - 25, whereas the latter feature strongly fractionated REE patterns and zircon e Hf( t ) values from - 10 to - 1. Both granites contain inherited zircons of ~1.8–1.9 or ~2.5 Ga. These geochemical characters testify to their derivation from re-melting distinct protoliths in ancient basement. Another Cretaceous magmatic sub-event has been entitled as the Gyeongsang volcanism, which is composed of bimodal calc-alkaline volcanic rocks of 94–55 Ma and granitic-hypabyssal granitic bodies of 72–70 Ma. Synthesizing the Mesozoic magmatic rocks across the KP, NCC and Japan can lead to the following highlights: (1) All Triassic granites in the NCC, KP and Japan have similar characteristics in petrology, chronology and geochemistry. Therefore, the NCC, KP and Japan tend to share the same tectonic setting during the Triassic, seemingly within the context of Indosinian orogensis. (2) Jurassic to earliest Cretaceous magmatic rocks in the NCC seem to define two episodes: episode A from 175 to 157 Ma and episode B from 157 to 135 Ma. Jurassic magmatic rocks in the KP span in age mainly from 190 to 170 Ma, whereas 160–135 Ma ones are rare. With the exception of ~197 Ma Funatsu granite, Jurassic magmatic rocks are absent in Japan. (3) Cretaceous granites in the KP have a peak age of ~110, ~20 Ma younger than those in the NCC, while Japan is exempt from ~130–100 Ma granites. (4) The spatial-temporal distribution and migratory characteristics of the

Development of geological model for Neogene sedimentary rocks in Japan -Representation of potential host rock environments in the NUMO 2015 Safety Case-

Development of geological model for Neogene sedimentary rocks in Japan -Representation of potential host rock environments in the NUMO 2015 Safety Case-

Hydrochemical disturbances measured in groundwater during the construction and operation of a large-scale underground facility in deep crystalline rock in Japan

Changes in the hydrochemical conditions of groundwater were evaluated following the construction of a large-scale underground facility at the Mizunami Underground Research Laboratory (MIU), Japan. The facility was constructed to a depth of 500 m in sedimentary and granitic rocks. Drawdown of the groundwater level in the range of several tens to hundreds of meters was observed up to hundreds of meters away from the shafts during the first ten years of facility construction and operation. Subsequent changes in groundwater chemistry occurred due to upconing of high-salinity groundwater from the deepest part of the shaft and the infiltration of low-salinity shallow groundwater. We predict that future deep groundwater chemistry in the vicinity of the MIU facility will resemble that of the present-day shallow groundwater. Multivariate statistical analysis provides fundamental insights into such a site. We found that the extent of hydrochemical variability related to MIU construction and operation was dependent on the distance from the facility shafts and galleries and on hydrogeological compartmentalization resulting from lithological boundaries (such as permeable conglomerates vs. more compact lithological units) and other features (such as faults or clay layers). We conclude that hydrochemical impact assessment of groundwater in low-permeability rock is essential prior to the construction of such a facility. This should include characterization of hydrogeological structures and compartments to propose suitable location of shafts and galleries.

The formation of rodingite in the Nagasaki metamorphic rocks at Nomo Peninsula, Kyushu, Japan – Zircon U–Pb and Hf isotopes and trace element evidence

AbstractRodingites occur in serpentine‐matrix mélange of the Nagasaki metamorphic rocks in Japan. Two types of rodingites can be distinguished on the basis of their mode of occurrence and mineralogical composition. One occurs as dikes, which contain a mineral assemblage of grossular, vesuvianite, diopside, apatite, titanite, and zircon. The other occurs as a block, which consists of zoisite, clinozoisite, diopside, chlorite, apatite, titanite, and zircon. The former type of rodingites posses two types of zircons: prismatic and porous. The prismatic zircons contain primary fluid inclusions indicating their crystallization in the presence of fluids. The porous zircons have extensive fractures filled by zircon, which are indicative of a hydrothermal origin. Both zircon types were thought to have formed under the influence of fluids. U–Pb ion probe analyses of prismatic zircons from the rodingites yield a weighted mean age of 108–105 Ma, suggesting the Early Cretaceous as the time of rodingitization in the subduction zone. Hafnium isotopic compositions of prismatic zircons are close to or overlap with the mid ocean ridge basalt (MORB) Hf isotopic ratio. This indicates that the fluid composition may have been reflected by the MORB composition during rodingitization. On the other hand, the low εHf values (11.8–18.9) of porous zircons suggest that they incorporate a small amount of Hf from fluid contaminated by subducted sediments. The rodingites are significantly enriched in Sr and depleted in large ion lithophile elements (LILE) (Cs, Rb, Ba). The fluid during rodingitization is able to extracts LILEs from the protolith of rodingites and adds Sr to the protolith of rodingites. The high field strength elements (HFSE) (Zr, Th, U, Nb, Ta) concentrations in the rodingites are similar to those of MORB, thus indicate their relatively immobile nature during rodingitization.

Rock physics model for interpreting elastic properties of soft sedimentary rocks

To study the rock physics model for soft sedimentary rocks widely distributed in Japan, the bimodal sand/shale mixture model, which has been proposed for sedimentary rocks, is applied to the seismic P- and S-wave logging velocity, density and porosity data. This model consists of the mixture of two different-size grains. Macroscopic elastic properties are derived from the Hashin-Strikman lower bounds, Hertz-Mindlin contact model and Gassmann’s equation. The changes of P-wave and shear moduli as functions of porosity, clay contents and confining pressure are calculated by the model and compared with the data obtained in three different soft sedimentary rocks in Japan. The model thus obtained is used for predicting porosity and clay content of the soft sedimentary rock using S-wave velocity and density logs. These applications reveal that the model can reproduce the remarkable features of soft sedimentary rocks, in which their elastic properties strongly depend on the grain size distribution and confining pressure.

The Inference of Geo-Mechanical Properties of Soft Rocks and their Degradation from Needle Penetration Tests

Needle penetration tests (NPTs) are used for inferring the uniaxial compressive strength of soft rocks, particularly in tunneling through squeezing rocks and foundations on weathered rocks in Japan. The device measures the applied load and the penetration depth of its needle. The ratio of applied load to penetration depth was originally called the needle penetration index (NPI). In this study, this device has been used to infer the geo-mechanical properties of soft rocks from Japan, Turkey, Indonesia, and Egypt. Various equations are presented to infer the geo-mechanical properties in terms of the NPI and compared with the experimental results. The possibility of evaluating the anisotropy of geo-mechanical properties is shown. Furthermore, the characterization of geo-mechanical properties of fault/fracture and slip (shear) surfaces is explained. Some additional equations are given to consider the degradation of geo-mechanical properties as a function of water content, weathering state, and number of cycles of freezing–thawing. Furthermore, the possibility of evaluating the time-dependency characteristics of soft rocks by needle penetration testing is discussed through experiments. It is shown that the effects of water content, weathering state, and number of cycles of freezing–thawing and time-dependency can be evaluated using the NPT technique.

秋田地域における女川層タイトオイルの可能性

The Onnagawa Shale is bio-siliceous, Monterey-like and the main source rock in Japan, particularly in Akita basin, with fairly high potential. It is 500m thick in average and has TOC of 2% in average, up to 5% in part, and HI of 500 mg/gC typically. The Onnagawa is under review in the light of Shale oil/gas, comparing the Monterey shale.As the first step, we have reviewed the Yuihara-Ayukawa field, where the largest commercial oil & gas production from the Onnagawa Shale is ongoing. In the field, various reservoirs, including Dolerite, Tuff and quartzose porcelanite probably fractured, seem to have a common gas-oil contact. In other words, they constitute one pressure system. The maturity of the hydrocarbon in this system is much higher than that of source rocks close to the reservoirs, which indicates normal migration process. We also have sub-commercial production or intense oil show from relatively tight reservoirs that is typically alternation of porcelanite and tuff. The maturity of the oil, however, is lower than that of commercial oils and close to that of early-matured source rocks around.In summary, we have two different hydrocarbon accumulations in one filed. One is productive, mature and probably migrated, and another is sub-commercial or non-productive so far, less matured and indigenous. In addition, we have other similar examples in the Akita basin and we think this less-matured oil group as a part of basin-wide shale oil system, where our field is located in the transition zone just above oil generation window. We expect a potential with an order of 100 million bbl in this basin including the kitchen. Now the first pilot test is being planned to apply horizontal drilling and massive stimulation treatment to “shale oil or tight oil” in this basin.

Experimental Measurements of Threshold Pressure for Modeling Saline Aquifers in Japan

In this study we evaluated threshold pressures of fine grained rocks in Japan. We used two methods, one is indirect method and the other is direct measurement. Mercury intrusion test (MIT) is the indirect method and the relations between threshold pressures and permeability coefficients results are consistent with existing data. But the threshold pressure obtained by MIT was a little lower than that by direct measurement. The reason for this difference might be that the MIT can’t take account of flow direction, though flow direction of direct measurement is perpendicular to the bedding plane. As direct method, we conducted threshold pressure measurements by stepwise way using CO2 and N2. Similar to the previous study, threshold pressure using N2 was higher than that using CO2.

Comparison of microbiological influences on the transport properties of intact mudstone and sandstone and its relevance to the geological disposal of radioactive waste

AbstractThe role of the microbial activity on the transport properties of host rocks for geological repositories, particularly in the far-field, is an area of active research. This paper compares results from experiments investigating changes in transport properties caused by microbial activity in sedimentary rocks in Japan (mudstones) and sandstone (UK).These experiments show that both Pseudomonas denitrificans and Pseudomonas aeruginosa appear to survive and thrive in pressurized flow-through column experiments which utilized host rock materials of relevance to radioactive waste disposal. Indeed, despite there being a difference in the numbers of organisms introduced into both biotic experiments, numbers appear to stabilize at ∼105 ml−1 at their completion. Post experimental imaging has highlighted the distinct differences in biofilm morphology, for the chosen rock types and bacteria, with Pseudomonas aeruginosa derived biofilms completely covering the surface of the sandstone host and Pseudomonas denitrificans forming biofilament structures. Regardless of substrate host or choice of microbe, microbial activity results in measurable changes in permeability. Such activity appears to influence changes in fluid flow and suggests that the transport of radionuclides through the far-field will be complicated by the presence of microbes.

CRYSTAL CHEMISTRY OF MONAZITE FROM THE GRANITIC ROCKS OF JAPAN: PETROGENETIC IMPLICATIONS

Electron-microprobe analyses were carried out on monazite from magnetite-series and ilmenite-series granitic rocks in Japan. All of the samples examined consist of monazite-(Ce), except for a unique case of monazite-(Sm) in the Shimo-ono ilmenite-series granitic pegmatite. The observed variations in their chemical composition are largely explained by the huttonite exchange [(Th + U) 4+ ↔Si 4+ ], and subordinately by the cheralite exchange [(Th + U) 4+ ↔2Ca 2+ ]. However, there are differences in the degree of contribution of the two exchanges between monazite grains from magnetite-series and ilmenite-series granitic rocks. The cheralite exchange is more important for monazite grains in ilmenite-series granitic rocks than for those in magnetite-series granitic rocks. Monazite grains in Japanese granitic rocks of these two series characteristically have a low cheralite component compared to those in S-type granites from various regions in the world, but chemical characteristics of ilmenite-series granitic rocks are more similar to S-type granitic rocks than those of the magnetite-series. The monazite grains of the Japanese granitic rocks show a continuous decrease in the slope of chondrite-normalized REE patterns from magnetite-series granites [(La/Sm)cn: 6.22–7.50] to ilmenite-series granitic pegmatite [(La/Sm)cn: 0.09–1.88] through magnetite-series granitic pegmatite [(La/Sm)cn: 2.25–3.70] and ilmenite-series granites [(La/Sm)cn: 2.13–4.56]. Thus, the REE compositions of the monazites reflect the degree of fractionation from granites to granitic pegmatites in both series. The same trend is confirmed by the (La/Nd)cn value, resulting in a positive correlation between (La/Nd)cn and (La/Sm)cn values of monazite from Japanese granitic rocks. Because the whole rock REE compositions of the magnetite-series and ilmenite-series granites show higher and lower (La/Sm)cn-(La/Nd)cn values, respectively, which are identical to the values of the respective granites-series monazites, we conclude that the chemical compositions (especially REE compositions) of monazite reflect the types (magnetite-series or ilmenite-series) and the degree of differentiation (granite or granitic pegmatite) of the granitic rocks in the subduction-related magmatic arcs.

Rock Physics Modeling of Dynamic and Static Young's Moduli of Soft Sedimentary Rocks

To interpret dynamic and static Young's moduli of soft sedimentary rocks, the Dvorkin-Gutierrez silty shale model, one of granular models is applied to the measured Young's moduli obtained from velocity logging data for the dynamic modulus and from laboratory mechanical test data for the static modulus. The Young's modulus for the rock is calculated by the Hashin-Strikman lower bound, Hertz-Mindlin contact model and Gassmann's equation. For modeling static Young's modulus, in the Hertz-Mindlin contact model, the shear modulus is calculated by incorporating the mixture of frictional and frictionless grain contacts into the model. The calculated dynamic and static Young's moduli are well consistent with the measured data for three different soft sedimentary rocks in Japan. This result demonstrates that the rock physics model can be used to predict the static moduli required in civil engineering applications from dynamic ones obtained from seismic velocities.