Petrology, geochemistry and paleogeographic reconstruction of the East Sulawesi Ophiolite, Indonesia

The East Sulawesi Ophiolite (ESO) is tectonically dismembered and widely distributed in Central and East Sulawesi. It comprises, from base to top, residual mantle peridotite and mafic–ultramafic cumulate through layered to isotropic gabbro, to sheeted dolerites and basaltic volcanic rocks. Residual peridotite is dominantly spinel lherzolite intercalated with harzburgite and dunite. Ultramafic rocks from different locations display significant differences in rock composition and mineral. However, the clinopyroxene of peridotite displays REE pattern similarities with those of mid-ocean ridge (MOR) origin, rather than those of suprasubduction zone (SSZ) origin. The gabbroic unit consists of massive gabbro, layered gabbro, mafic and ultramafic cumulate and anorthosite. The observed crystallization sequence of gabbroic unit, which is olivine→(spinel)→plagioclase→clinopyroxene→(orthopyroxene)→(hornblende), and the mineral chemistry data indicate that the ESO gabbro has similarities with MOR setting.Major and trace element geochemistry of basalt and dolerite suggests MOR, oceanic plateau and minor SSZ origins. A possible oceanic plateau origin is supported by the following: (i) the 15-km thickness is comparable with the thickness of oceanic plateau rather than normal oceanic lithosphere; (ii) there are no or only minor olivine phenocrysts in the basalt; and (iii) predominance of aphyric texture in the basalts. The REE pattern of ESO basalt exhibits N-MORB-like signatures. However, a negative Nb anomaly in the trace element spider diagram may be attributed to mantle heterogeneity of an OPB source.The geochemical variations and disparities for both peridotite and basalt and the noncogenetic relationship between crust and mantle sections in several locations suggest that the ESO may have been formed at one tectonic setting and was later overprinted by magmatism in different environments through its birth to emplacement. A possible Cretaceous origin of an oceanic plateau component of the ESO is indicated on the basis of calculated paleopositions using plate trajectory analyses together with previously published paleolatitude data. The ESO can be traced back to the proximity of the presently active region of the SW Pacific Superplume.     

A Study Of The Atmospheric Boundary Layer Using Radon And Air Pollutants As Tracers

Concentrations of radon ²²²Rn andair pollutants, meteorological parametersnear the surface and vertical profiles of meteorological elements were measured atUchio (Okayama City, Okayama Prefecture, Japan) 12 km north from the coast ofthe Inland Sea of Japan. In the nighttime, the ²²²Rn concentration increased in the case of weak winds, but did not increase as much in the case of moderate or strong winds, as had been expected. In the daytime, the ²²²Rn concentrationheld at a slightly higher than average level for the period from sunrise to about 1100 JST. It is considered that this phenomenon is due to a period of morning calm, that is, a transition period from land breeze to sea breeze.NO, which is sensitive to traffic volume,brought information concerning advection.Oxidant concentrations,which reflect the availability of sunlight,acted in the reverse manner to ²²²Rnconcentrations. Thus, a set of ²²²Rn and air pollutants could provide useful information regarding the local conditions of the atmospheric boundary layer.     

Shape detection of multiple subsurface cavities by particle filtering with elastic wave propagation

A numerical technique for detecting the number and shape of subsurface cavities is presented, applying the particle filter and the parametric level set method to elastic wave propagation under the ground. When subsurface cavities exist, the elastic wave propagating in the ground is reflected at the boundary faces of the cavities. Observing the velocity of the reflection wave at the surface of a ground that includes multiple cavities and parameterizing the shape of the cavities by the parametric level function, both the number and the shape of the cavities can be identified by the particle filter. Numerical experimentation for detecting multiple cavities is conducted with synthetic observation data. The results show that the proposed technique enables the number of cavities to be identified by the number of peaks in the posterior probabilistic distribution function and solves geometric inverse problems by estimating the shape of the cavities through the parameter identification of the level set function.     

Characteristics of earthquake-induced landslides in a heavy snowfall region—landslides triggered by the northern Nagano prefecture earthquake, March 12, 2011, Japan

The northern Nagano Prefecture earthquake, M_JMA?6.7 (Mw?6.2), which is inferred to have been triggered by the huge (Mw?9.0) March 11, 2011 Tohoku earthquake, occurred on March 12, 2011, in northern Nagano Prefecture, an area in Japan famous for heavy snowfall. A large number of landslides were triggered by the 12 March earthquake, and it caused building damage in the area of the epicenter. To clarify characteristics of the distribution and dynamic behavior of these landslides, we analyzed aerial photographs and conducted field surveys in and around the epicentral area. Large-scale landslides with long distance run-outs are a remarkable characteristic of the landslides induced by this earthquake. The long travel distance is considered to be related to the thick snowpack at the time the earthquake occurred. Moderate scale deep-seated landslides and shallow landslides were also observed in the study area. Based on an analysis of landslides with the active fault on which the earthquake is believed to have occurred, most of these landslides were distributed on the hanging wall of the active fault, within a distance of 12?km from the fault.     

Occurrence and chemical composition of the Eoarchean carbonate rocks of the Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador,Canada

The Eoarchean Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador, Canada, contain some of the world's oldest carbonate rocks. This work attempted to reveal the origin of the carbonate rocks and estimate the surface environmental conditions of the early Earth based on their occurrence and geochemistry. They occur together with mafic and ultramafic rocks in Pangertok Inlet and St. John's Harbour South, whereas they are interlayered with pelitic rock layers with quartzofeldspathic mineral assemblages in St. John's Harbour East and Big Island. The geological occurrence suggests that the formers were formed around hydrothermal fields, whereas the latters were deposited near a continental margin. Some carbonate rocks have high SiO₂, Al₂O₃, and Zr contents, indicating that the silicification and involvement of detrital materials influenced their composition; thus, pure carbonate rocks were selected using a combined filter of the SiO₂, TiO_2, Al₂O₃, Zr, and Ba contents. The selected carbonate rocks have positive La, Eu, Gd, Y, U, Pb, and Sr anomalies, negative Nb, Zr, and Hf anomalies, and relatively small enrichment in heavy rare earth elements (HREEs). The La and Y anomalies suggest that they originated from chemical sediments precipitated from seawater. On the other hand, the small HREE-enrichment suggests that REEs were mainly dissolved as REE-carbonate complexes in seawater or that the riverine influxes were dominated by the detritus of Eoarchean continental crusts, presumably composed of HREE-depleted TTG. The U anomaly suggests that uranium was more dissolved than Th as U-bearing carbonate complexes in seawater. The Nulliak carbonate rocks also show a positive correlation between Y and Eu anomaly values, suggesting that the precipitation of iron-oxyhydroxide causing the Y anomaly was more significant near the hydrothermal fields than the continental margin, consistent with an alkaline hydrothermal model.     

Geochemistry of eclogite‐ and blueschist‐facies rocks from the Bantimala Complex,South Sulawesi,Indonesia: Protolith origin and tectonic setting

We present the first data on bulk‐rock major and trace element compositions for a suite of eclogite‐ and blueschist‐facies rocks from the Bantimala Complex, Indonesia, with the aim of better constraining the protolith origins and nature of the subducted crust. The eclogites can be classified into two groups: glaucophane‐rich eclogite and glaucophane‐free eclogite, whereas the blueschists are divided into albite–epidote glaucophanite and quartz–glaucophane schists. SiO₂ contents of the eclogites are 43.3–49.6 wt%, with Na₂O + K₂O contents 3.7–4.7 wt%. The blueschists show a wider range of compositions, with SiO₂ = 40.7–63.8 wt% and Na₂O + K₂O = 2.7–4.5 wt%. Trace element data suggest that the eclogite protoliths include both enriched and normal mid‐oceanic ridge basalt (E‐MORB and N‐MORB) and also gabbroic cumulates. The blueschists show more variation in protoliths, which include N‐MORB, Oceanic Island Basalt (OIB) and Island Arc Basalt (IAB). Plots of element concentrations against the immobile Zr show considerable mobility of large ion lithophiles but not of high field‐strength elements during high‐pressure metamorphism, and indicate that the high SiO₂ content of some blueschists is probably due to metasomatism by a LILE‐rich siliceous aqueous fluid. Strong correlations between K, Rb, Ba and Cs suggests that enrichment of these elements occurred by a single process. All the protoliths were subducted, metamorphosed to blueschist/eclogite‐facies and subsequently exhumed. It is noteworthy that the samples deduced to have come from thicker‐crust environments (OIB, IAB) were subducted to shallower depths (blueschist‐facies) than MORB‐derived samples, all except one of which reached eclogite‐facies conditions. The geochemical data of this study demonstrate the variety of ocean floor types that were subducted under the southeast margin of Sundaland in the late Jurassic period.     

Non-stochastic colonization by pioneer plants after deglaciation in a polar oasis of the Canadian High Arctic

Initial plant colonization is critical in determining subsequent ecosystem development. In a High-Arctic oasis showing atypical “directional primary succession”, we quantified the microhabitat characteristics associated with colonization by pioneer vascular plants of a bare moraine. The study moraine, formed during the Little Ice Age, is located within the proglacial area at the southern front of Arklio Glacier, Ellesmere Island, Canada. We established two line-transects on this moraine to quantify microhabitats for vascular species. Microsites favorable for plants were concave depressions, probably increasing the likelihood of colonization. At microsites distant from stable boulders, which probably protect seeds/seedlings from wind desiccation, plant colonization was less likely. Furthermore, favorable microhabitat properties differed depending on topographical location within the moraine, suggesting that, even within a single moraine, microhabitats favorable for plant colonization are heterogeneously-distributed. This moraine was characterized by two major pioneer species, Epilobium latifolium and Salix arctica. Their species-specific microhabitat requirements highlight the importance of biotic factors in colonization processes. Favorable sites for plants are generally distributed at random in harsh environments. However, we showed that initial plant colonization is a deterministic process rather than random, indicating the possibility of non-stochastic processes even during the early phase of ecosystem development in High-Arctic ecosystems.     

日本环境保全型农业的综述:发展历史、挑战及新机遇（英文）

农业生态系统是世界上最大的人类管理的生态系统。环境保全型农业的发展对扭转世界上生物多样性巨大损失的局面意义重大。全球重要农业文化遗产(GIAHS)项目是由联合国粮农组织(FAO)发起的以保护和动态管理传统农业知识系统及其景观为目标的国际性项目。日本农林水产省(MAFF)1992年开始高度重视现代农业生产对环境的负面影响。能登半岛和佐渡市被认定为发达国家中最早的GIAHS试点地,这也显示了日本地方层面保护传统农业生态系统的决心。本文综述了日本环境保全型农业发展的历史过程,现状,面临的挑战和新的机遇。日本现有的环境保全型农业包括:减少化肥和农药用量的做法,重视保护生物多样性的农法,有机农业等等。本文重点介绍了北陆地区的环境保全型农业发展的情况,尤其是石川县能登地区和新泻县佐渡市的情况以及最新的案例分析。本文使用最新的政府报告等官方文件,统计数据和学术论文进行分析并初步探讨如何进一步发展和扩大环境保全型农业的政策建议。本文分析环境保全型农业推广的问题并介绍了环境保全型农产品的市场价格的研究成果。认为重视农民的利益,鼓励城市居民,科研人员以及私营企业等多方面的参与,以及地方政府支持环保产品拓宽销路是环境保全型农业能得到切实发展的关键所在。     

Surface morphological features of boulders on Asteroid 25143 Itokawa

On the sub-kilometer S-type asteroid, 25143 Itokawa, some boulders on rough terrains seem to be exposed without any powdery material covering. Based on surface morphological features, there are two major types of boulders: one has rounded edges and corners (rounded boulders), while the other has angular edges and corners (angular boulders). The surface features of the rounded boulders suggest that they have hardness heterogeneity and that some may be breccias. The angular boulders appear to be more resistant to impact disruption than the rounded ones, which may be due to a difference in lithology. The major constituents of Itokawa may be LL chondrite-like brecciated lithology (rounded boulders) along with a remarkable number of boulders suggesting that lithology is atypical among LL chondrites (angular boulders). Some of both types of boulders contain intersecting and stepped planar foliations. Comparison with meteorite ALH76009 suggests that the planar foliations may be marks where rocks were torn apart. As lithified breccias cannot be formed on present-day sub-kilometer-sized Itokawa, it is reasonable that boulders with various lithologies on Itokawa were formed on its large ancestor(s). The rubble-pile structure of Itokawa suggested by its low density (∼1.9 g/cm³) indicates that boulders on Itokawa are reassembled fragments formed by catastrophic disruption of large ancestor(s).     

Comparison of rhyolites from continental rift,continental arc and oceanic island arc: Implication for the mechanism of silicic magma generation

We discuss the chemical compositions of rhyolites from three distinct tectonic settings: (i) the continental rift from Ethiopia (both Oligocene–Miocene and Quaternary rhyolites); (ii) the early Miocene continental arc of Japan (the Mt Wasso rhyolites related to the rifting of the Japan Sea); and (iii) the oceanic Izu–Bonin Island Arc. The comparison reveals that the oceanic island arc rhyolites have high contents of CaO, Al₂O₃, and Sr, and extremely low abundance of trace elements including K₂O. In contrast, the Ethiopian continental rift rhyolites are characterized by low contents of CaO, Al₂O₃, and Sr, and high contents of K₂O, and are enriched in the whole range of trace elements. The continental arc Mt Wasso rhyolites are apparently low in Nb content, although they display similar chemical trends to those of the Ethiopian rhyolites. This obvious difference in the chemical signatures of the rhyolites from the three tectonic settings is the consequence of their derivation from different sources. The implication of this result is that fractional crystallization processes were dominant in the rift‐related rhyolites both from continental rift and continental arc regardless of the prevailing tectonic setting and the nature of the crust (age, thickness, composition), whereas the oceanic island arc rhyolites may form through partial melting of young, mafic crust.