Radiolarian Age of Manganese Ore and Red Chert from the Ananai Stratiform Manganese Deposit in the Northern Chichibu Belt, Central Shikoku, Japan

Abstract. We obtain radiolarian fossils such as Follicucullus monacanthus, Pseudoalbaillella aff. globosa, Pseudoalbaillella cf fusiformis , and Pseudoalbaillella spp. belonging to the Pseudoalbaillella globosa and Follicucullus monacanthus Zones from manganese ore and associated red chert of the Ananai stratiform manganese deposit in the Northern Chichibu Belt, central Shikoku. The depositional age of the Ananai ore deposit is constrained as Guadalupian (Middle Permian) that is between 270.6 and 260.4 Ma in the updated geologic time scale.     

Seismic performance evaluation of non‐structural components: drywall partitions

As the first part of non‐structural component test series, interior drywall partitions are selected for an experimental program. This test series will cover non‐structural components that are significant in the economic losses in buildings subjected to seismic loading, namely interior drywall partitions, exterior cladding and window glasses, and ceilings. Four full‐scale drywall partitions with light‐gage steel stud framing were tested to observe damage in cyclic loading conditions. Effects of a door and an intersecting wall on the behaviour of drywall partition are studied. Damage was concentrated to perimeter regions where gypsum boards made contacts with ceiling, floor, or columns. Dynamic loading did not amplify the damage on a drywall partition over the damage observed from the quasi‐static test. Damage–repair cost relationships show that the repair cost reaches almost the initial cost under 2% radian interstorey drift. Copyright © 2006 John Wiley & Sons, Ltd.     

Preferred orientation of phyllosilicate [001] in matrix of Murchison meteorite and possible mechanisms of generating the oriented texture in chondrites

Preferred orientation of the dominant phyllosilicate phase (serpentine) in the matrix of the Murchison meteorite (C2) was determined by X-ray pole figure goniometry. The basal plane (001) of the phyllosilicate shows a clear preferred orientation of an axial concentration type. The preferred orientation is very weak in comparison with the orientations of known terrestrial tectonites, and it resembles the weakest case observed in the loosely consolidated clayey sediments from the deep ocean bottom. However, gentle sedimentation of platy phyllosilicate grains on a flat surface under a weak gravity field does not generate a sufficient preferred orientation. It is suggested that the preferred orientation in the matrix of Murchison was generated by uniaxial compaction, and the magnitude of strain to give rise to the observed degree of preferred orientation is evaluated as ?9%. There are two possible explanations of the deformation: dynamic compression caused by impact, and static compaction in a parent body. Though the latter case appears to be appropriate in the present case, it is not straightforward, however, to conclude that the suggested deformation is caused by burial compaction along gravity under lithostatic stress in a small primitive parent body.     

GPR survey and physical measurements of sea ice in Quilty Bay,Larsemann hills,East Antarctica and its correlation with local atmospheric parameters

Sea ice formation in Quilty Bay, East Antarctica shows a strong relationship with climatic conditions and its spatial variation is established by GPR survey over the sea ice during the austral winters. The study also evaluates the variability of sea ice thickness and extent with local weather parameters between 2010 and 2014. Profiling on sea ice in Quilty Bay shows that sea ice thickness decreases gradually towards east. The overall thickness of sea ice is considerably less at the centre of the bay as compared to the coastal side. Two types of fast ice layers have been delineated from GPR surveys i.e. top layer fast ice which incorporates very low density surface snow and underlying high density fast ice i.e. with melt water pockets. Development of sea ice is influenced by persistent easterly winds, temperature fluctuations and ocean currents. Sea ice reveal average annual cyclic trend in Quilty Bay with maximum development in the year 2013 (157.54 cm) and the minimum development has been observed in the year 2010 (99.04 cm).The cyclic pattern of average sea ice accumulation data show perfect inverse correlation with surface air temperature, with measure of reliability R² = 0.93. However, moderate (R² = 0.52) and good (R² = 0.69) degree of inverse relationship is observed with surface snow and overall sea ice (snow and ice) respectively. With 0.46 °C change in temperature, there is 33% change in sea ice condition in Quilty Bay which may remain same as far as ice extents in the region. Besides this easterly winds play a vital role in controlling the snow/ice distribution patterns as reflected by isopach maps.     

Depositional Age of a Fossil Whale Bone from São Paulo Ridge,South Atlantic Ocean,Based on Os Isotope Stratigraphy of a Ferromanganese Crust

Whale carcasses (whale falls) deposited on the deep seafloor are associated with a distinctive biotic community. A fossil whale bone recovered from São Paulo Ridge, South Atlantic Ocean, during cruise YK13–04 Leg 1 of R/V Yokosuka was covered by a ferromanganese (Fe–Mn) crust approximately 9 mm thick. Here, we report an age constraint for this fossil bone on the basis of Os isotopic stratigraphy (¹⁸⁷Os/¹⁸⁸Os ratio) of the Fe–Mn crust. Major‐ and trace‐element compositions of the crust are similar to those of Fe–Mn crusts of predominantly hydrogenous origin. Rare earth element concentrations in samples of the crust, normalized with respect to Post‐Archean average Australian Shale, exhibit flat patterns with positive Ce and negative Y anomalies. These results indicate that the Fe–Mn crust consists predominantly of hydrogenous components and that it preserves the Os isotope composition of seawater at the time of its deposition. ¹⁸⁷Os/¹⁸⁸Os ratios of three Fe–Mn crust samples increased from 0.904 to 1.068 in ascending stratigraphic order. The value of 1.068 from the surface slice (0–3 mm depth in the crust) was identical to that of present‐day seawater within error (~1.06). The value of 0.904 from the basal slice (6–9 mm) equaled seawater values from ca. 4–5 Ma. Because it is unknown how long the bone lay on the seafloor before the Fe–Mn crust was deposited, the Os stratigraphic age of ca. 5 Ma is a minimum age of the fossil. This is the first application, to our knowledge, of marine Os isotope stratigraphy for determining the age of a fossil whale bone. Such data may offer valuable insights into the evolution of the whale‐fall biotic community.     

The high-pressure and temperature equation of state of a majorite solid solution in the system of Mg4Si4O12-Mg3Al2Si3O12

The high-pressure and temperature equation of state of majorite solid solution, Mj_0.8Py_0.2, was determined up to 23 GPa and 773 K with energy-dispersive synchrotron X-ray diffraction at high pressure and high temperature using the single- and double-stage configurations of the multianvil apparatuses, MAX80 and 90. The X-ray diffraction data of the majorite sample were analyzed using the WPPD (whole-powder-pattern decomposition) method to obtain the lattice parameters. A least-squares fitting using the third-order Birch-Murnaghan equation of state yields the isothermal bulk modulus, K _T0  = 156 GPa, its pressure derivative, K′ = 4.4(±0.3), and temperature derivative (∂K _T /∂T) _P = −1.9(±0.3)× 10⁻² GPa/K, assuming that the thermal expansion coefficient is similar to that of pyrope-almandine solid solution. Received: 5 October 1998 / Revised, accepted: 24 June 1999     

A Late Holocene geomagnetic secular variation record from Erhai Lake, southwest China

A secular variation record of the geomagnetic field direction for the last 6.5  kyr has been obtained from the magnetization of sediment cores from Erhai Lake, southwest China. In order to make a comparison with this record, secular variation in east-central China was investigated by combining available magnetic field data from historical records and archaeomagnetic measurements since about 350 bc . The secular variation in Erhai Lake shows features consistent with the combined record, except for the oldest three observed declination swings in Sian from 720 to 900 ad . Many features of declination and inclination in China also occur in Japan. From 500 to 1000 ad , declination was westerly ranging from about −20° to −5° in Erhai Lake, east-central China, and Japan.     

Rare Earth Elements as an Indicator to Origins of Skarn Deposits: Examples of the Kamioka Zn-Pb and Yoshiwara-Sannotake Cu(–Fe) Deposits in Japan

Abstract: Systematic data of rare earth elements (REEs) are presented in order to put some constraints on the origin of hydrothermal fluids responsible for two contrastive skarn deposits in Japan; the Kamioka Zn-Pb and Yoshiwara-Sannotake Cu(-Fe) deposits. Carbon and oxygen isotopic studies have demonstrated that the hydrothermal fluids responsible for the Kamioka Zn-Pb deposits are of meteoric water origin whereas those for the Yoshiwara-Sannotake Cu(-Fe) deposits are of magmatic water origin. The REE abundances of epidote skarn derived from aluminous rocks, garnet and clinopyroxene in calcic exoskarn derived from limestone, and interstitial calcite associated with sulfide minerals were determined for these contrastive skarn deposits by inductively-coupled plasma mass spectrometry (ICP-MS). A significant difference in the REE concentrations is not found between epidote skarn and aluminous original rock (plagioclase-clinopyroxene rock, called Inishi rock) from the Kamioka Zn-Pb deposits, indicating that the REEs are generally immobile during the formation of epidote skarn, and that the REE concentrations of the hydrothermal fluid are considerably low relative to the aluminous original rock. In contrast, the epidote skarn exhibits enrichment of Eu with increasing total REE concentrations relative to the aluminous original rock (quartz diorite) in the Yoshiwara-Sannotake Cu(-Fe) deposits, implying a contribution of magmatic fluid derived from granitoids during the skarn formation. Limestone generally has much lower REE concentrations related to surrounding aluminous rocks, and thus the REE concentrations of garnet and clinopyroxene in calcic exoskarn, originated from limestone, are variable due to the interaction with the hydrothermal fluids. The chondrite-normalized REE patterns of garnet, clinopyroxene, and interstitial calcite exactly provide useful information on origins of hydrothermal fluids. The REE patterns of these minerals from the Kamioka Zn-Pb deposits show lower (Pr/Yb)cn ratios, and negative Ce and Eu anomalies inherited from limestone with the decrease of This suggests that the hydrothermal fluids responsible for the Kamioka Zn-Pb deposits were depleted in REEs, and were not magmatic water in origin, but presumably meteoric one. In striking contrast, the REE patterns of exoskarn minerals and calcite from the Yoshiwara-Sannotake Cu(-Fe) deposits exhibit a positive Eu anomaly, and high (Pr/Yb)cn ratios with the considerable increase of σREE and the disappearance of negative Ce anomaly, implying that the fluids were dominantly of magmatic origin. The REE indices are very likely to be an excellent indicator to origins of the skarn deposits.     

Quantitative investigation on collapse margin of steel high-rise buildings subjected to extremely severe earthquakes

Reponses of structures subjected to severe earthquakes sometimes significantly surpass what was considered in the design. It is important to investigate the failure mechanism and collapse margin of structures beyond design, especially for high-rise buildings. In this study, steel high-rise buildings using either square concrete-filled-tube (CFT) columns or steel tube columns are designed. A detailed three-dimensional (3D) structural model is developed to analyze the seismic behavior of a steel high-rise towards a complete collapse. The effectiveness is verified by both component tests and a full-scale shaking table test. The collapse margin, which is defined as the ratio of PGA between the collapse level to the design major earthquake level (Level 2), is quantified by a series of numerical simulations using incremental dynamic analyses (IDA). The baseline building using CFT columns collapsed with a weak first story mechanism and presented a collapse margin ranging from 10 to 20. The significant variation in the collapse margin was caused by the different characteristics of the input ground motions. The building using equivalent steel columns collapsed earlier due to the significant shortening of the locally buckled columns, exhibiting only 57% of the collapse margin of the baseline building. The influence of reducing the height of the first story was quite significant. The shortened first story not only enlarged the collapse margin by 20%, but also changed the collapse mode.     

A zone of columnar joints beneath the roof of a granitic pluton: The Okueyama granite,southwestern Japan

Igneous rocks are fractured during cooling from magma to form cooling joints, which are typically columnar joints in volcanic rocks, while orthogonal joints are considered typical for plutonic rocks. We performed a 3D study of joint systems in a granitic batholith of the Okueyama granite in western Japan, which has its roof and its internal structures from the roof to 1000 m downward exposed. We used an unmanned aerial vehicle (UAV) to observe the joints in outcrops from various angles. Based on our study, we propose a schematic model for joint systems in a granitic pluton. A granitic pluton has zones of rock columns below the roof and next to the wall. The rock column zone below the roof is as thick as 300 m, and its higher portions form steep cliffs, probably because of increased resistance to weathering. The axes of the rock columns are nearly vertical below the roof and gently plunge next to the walls, with high intersection angles with the wall. The distribution of columnar joints near only the roof and walls suggests that the granite cooled more rapidly near the roof and walls than in the core of the pluton. When the granite was jointed by parallel joints during cooling, the rock slabs between the parallel joints near the roof and the walls are subdivided into columns with polygonal cross-sections. This suggests that the granite was fractured by parallel joints at a temperature immediately below the solidus, after which the rock slabs were subdivided into rock columns during further cooling.