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Assessment of widely used methods to derive depositional ages from detrital zircon populations

geoscience Frontiers 2019年第4期10卷 1421-1435页

作者： Daniel S.Coutts William A.Matthews Stephen M.Hubbard department of geoscience University of Calgary

The calculation of a maximum depositional age(MDA)from a detrital zircon sample can provide insight into a variety of geological ***,the impact of sample size and calculation method on the accuracy of a resulting MDA has not been *** use large populations of synthetic zircon dates(N≈25,000)to analyze the impact of varying sample size(n),measurement uncertainty,and the abundance of neardepositional-age zircons on the accuracy and uncertainty of 9 commonly used MDA calculation ***,a new method,the youngest statistical population is *** each method,500 samples of n synthetic dates were drawn from the parent population and MDAs were *** mean and standard deviation of each method ove r the 500 trials at each n-value(50-1000,in increments of 50)were compa red to the known depositional age of the synthetic population and used to compare the methods quantitatively in two simulation *** first simulation scenario varied the proportion of near-depositional-age grains in the synthetic *** second scenario varied the uncertainty of the dates used to calculate the *** sample size initially decreased the mean residual error and standard deviation calculated by each *** higher n-values(>~300 grains),calculated MDAs changed more slowly and the mean resid ual error increased or decreased depending on the method *** the p roportion of near-depositional-age grains and lowering measurement uncertainty decreased the number of measurements required for the calculated MDAs to stabilize and decreased the standard deviation in calculated MDAs of the 500 *** of the two simulation scenarios show that the most successful way to increase the accuracy of a calculated M DA is by acquiring a large number of low-uncertainty measurements(300300)approach is used if the calculation of accurate MDAs are key to research *** acquisition method s,such as high-to moderate-precision m

关键词： Detrital zircon Maximum depositional age Geochronology Basin chronology LA-ICP-MS

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Is plate tectonics needed to evolve technological species on exoplanets?

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geoscience Frontiers 2016年第4期7卷 573-580页

作者： Robert J.Stern geoscience department University of Texas at Dallas

As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species. This essay considers this question, focusing on tectonically active roclw （silicate） planets, like Earth, Venus, and Mars. The development of technological species on Earth provides key insights for understanding evolution on exoplanets, including the likely role that plate tectonics may play. An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime, as it cools and its lithosphere thickens, strengthens, and becomes denser. These include magma ocean, various styles of stagnant lid, and perhaps plate tectonics. Abundant liquid water favors both life and plate tectonics. Ocean is required for early evolution of diverse single-celled organisms, then colonies of cells which specialized further to form guts, ap- pendages, and sensory organisms up to the complexity of fish （central nervous system, appendages, eyes）. Large expanses of dry land also begin in the ocean, today produced above subduction zones in juvenile arcs and by their coalescence to form continents, although it is not clear that plate tectonics was required to create continental crust on Earth. Dry land of continents is required for further evolution of technological species, where modification of appendages for grasping and manipulating, and improve- ment of eyes and central nervous system could be perfected. These bioassets allowed intelligent crea- tures to examine the night sky and wonder, the beginning of abstract thinking, including religion and science. Technology arises from the exigencies of daily living such as tool-making, agriculture, clothing, and weapons, but the pace of innovation accelerates once it is allied with science. Finally, the importance of plate tectonics for devel

关键词： Plate tectonics Exoplanets Planetary science Intelligent life

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Earth's Solid Inner Core: Seismic Implications of Freezing and Melting

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Journal of Earth Science 2013年第5期24卷 683-698页

作者： Vernon F Cormier Januka Attanayake department of Physics University of Connecticut Center for Integrative geoscience University of Connecticut Center for Integrative geoscience University of Connecticut

Seismic P velocity structure is determined for the upper 500 km of the inner core and lowermost 200 km of the outer core from differential travel times and amplitude ratios. Results confirm the existence of a globally uniform F region of reduced P velocity gradient in the lowermost outer core, consistent with iron enrichment near the boundary of a solidifying inner core. P velocity of the inner core between the longitudes 45~E and 180~E （quasi-Eastern Hemisphere） is greater than or equal to that of an AK135-F reference model whereas that between 180~W and 45~E （quasi-Western Hemisphere） is less than that of the reference model Observation of this heterogeneity to a depth of 550 km below the inner core and the existence of transitions rather than sharp boundaries between quasi-hemispheres favor either no or very slow inner core super rotation or oscillations with respect to the mantle. Degree- one seismic heterogeneity may be best explained by active inner core freezing beneath the equatorial Indian Ocean dominating structure in the quasi-Eastern Hemisphere and inner core melting beneath equatorial Pacific dominating structure in the quasi-Western Hemisphere. Variations in waveforms also suRgest the existence of smaller-scale （1 to 100 km） heterogeneity.

关键词： Earth's inner core seismic structure geodynamo.

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Deriving a minimum set of viewpoints for maximum coverage over any given digital elevation model data

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International Journal of Digital Earth 2016年第12期9卷 1153-1167页

作者： Xuan Shi Bowei Xue department of geoscience University of ArkansasFayettevilleARUSA

This paper introduces how to automatically derive a minimum set of viewpoints for maximum coverage over a large scale of digital terrain *** is a typical data and computation-intensive research covering a series of geocomputation tasks that have not been implemented efficiently or optimally in prior *** paper introduces a three-step computational solution to resolve the *** any given digital elevation model(DEM)data,automatic generation of control viewpoints is the first step through map algebra calculation and hydrological modeling *** each viewpoint,the viewshed calculation then has to be *** combined viewshed derived from the viewshed of all viewpoints establishes the maximum viewshed coverage of the given ***,detecting the minimum set of viewpoints for the maximum coverage is a Non-deterministic Polynomial-time hard *** outcome of the computation has broader societal impacts since the research questions and solutions can be adapted into realworld application and decision-making practice,such as the distribution,optimization and management of telecommunication infrastructure and wildfire observation towers,and military tactics and operations dependent upon landscape and terrain features.

关键词： Minimum set maximum coverage viewshed digital terrain optimization

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Calcium isotope compositions as a means to trace carbonate recycling

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National Science Review 2022年第6期9卷 8-10页

作者： Shichun Huang Stein B.Jacobsen department of geoscience University of Nevada department of Earth and Planetary Sciences Harvard University

Marine carbonates, such as sedimentary carbonates and secondary carbonates formed during marine alteration processes, are returned to the mantle at subduction zones, and their fates regulate the global carbon cycle. S... 详细信息

关键词： Carbonates

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Analysis of unlined pressure shafts and tunnels of selected Norwegian hydropower projects

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第3期10卷 486-512页

作者： Chhatra Bahadur Basnet Krishna Kanta Panthi department of geoscience and Petroleum Norwegian University of Science and Technology

Norwegian hydropower industry has more than 100 years of experiences in constructing more than4000 km-long unlined pressure shafts and tunnels with maximum static head of 1047 m（equivalent to almost 10.5 MPa） reached at unlined pressure tunnel of Nye Tyin project. Experiences gained from construction and operation of these unlined pressure shafts and tunnels were the foundation to develop design criteria and principles applied in Norway and some other countries. In addition to the confinement criteria, Norwegian state-of-the-art design principle for unlined pressure shaft and tunnel is that the minor principal stress at the location of unlined pressure shaft or tunnel should be more than the water pressure in the shaft or tunnel. This condition of the minor principal stress is prerequisite for the hydraulic jacking/splitting not to occur through joints and fractures in rock mass. Another common problem in unlined pressure shafts and tunnels is water leakage through hydraulically splitted joints or pre-existing open joints. This article reviews some of the first attempts of the use of unlined pressure shaft and tunnel concepts in Norway, highlights major failure cases and two successful cases of significance, applies Norwegian criteria to the cases and reviews and evaluates triggering factors for *** article further evaluates detailed engineering geology of failure cases and also assesses common geological features that could have aggravated the failure. The minor principal stress is investigated and quantified along unlined shaft and tunnel alignment of six selected project cases by using threedimensional numerical model. Furthermore, conditions of failure through pre-existing open joints by hydraulic jacking and leakage are assessed by using two-dimensional fluid flow analysis. Finally, both favorable and unfavorable ground conditions required for the applicability of Norwegian confinement criteria in locating the unlined pressure shafts and tunnels for ge

关键词： Hydropower projects Unlined pressure shafts and tunnels Minor principal stress Hydraulic jacking Water leakage

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Maximizing biomass utilization: An integrated strategy for coproducing multiple chemicals

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Journal of Energy Chemistry 2025年第01期 180-191页

作者： Byeongchan Ahn Sua Jo Jonggeol Na J.Jay Liu Young-Ju Kim Wangyun Won department of Chemical and Biological Engineering Korea University department of Chemical Engineering (Integrated process) Kyung Hee University department of Chemical Engineering and Materials Science Ewha Womans University department of Chemical Engineering Pukyong National University Resources Engineering Plant Research department Korea Institute of Geoscience and Mineral Resources

Lignocellulosic biomass is one of the viable solutions to alleviate the global warming. However, the limited utilization of biomass majorly focused on cellulose and hemicellulose restricts the economic and environmental feasibilities. To cope with this issue, we proposed an integrated process of co-producing 1,6-hexanediol（1,6-HDO） with tetrahydrofuran and adipic acid from biomass, referred to as Strategy A. To compare the impacts of lignin upgrading and feedstock, Strategy B, which co-produces tetrahydrofuran alone, and Strategy C, which is the traditional route to produce 1,6-HDO from fossil fuels, were used. Heat networks are also designed to reduce operating costs and indirect carbon emissions due to energy consumption, saving 87% and 83% of the heat and cooling requirements, respectively, in Strategy A. The market competitiveness of Strategy A was evaluated by determining the minimum selling price through techno-economic analysis, and sustainability was thoroughly investigated by quantifying the environmental impacts through both midpoint and endpoint life-cycle assessments（LCAs）.Strategy A was found to be the most favorable both economically（USRDSCHARDOLLAR3,402/ton） and environmentally（-26.9 kg CO2eq.）. This indicates that lignin valorization is not only economically but also environmentally preferred. Finally, changes in economic and environmental feasibilities depending on economic, process, and environmental parameters were investigated using sensitivity and uncertainty analyses. The results of these analyses provide valuable insight into bio-based chemical production.

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Principles of rockbolting design

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第3期9卷 14-32页

作者： Charlie C. Li department of geoscience and Petroleum The Norwegian University of Science and Technology Norway

This article introduces the principles of underground rockbolting *** items discussed include underground loading conditions,natural pressure zone around an underground opening,design methodologies,selection of rockbolt types,determination of bolt length and spacing,factor of safety,and compatibility between support *** types of rockbolting used in engineering practise are also *** traditional principle of selecting strong rockbolts is valid only in conditions of low in situ stresses in the rock ***-absorbing rockbolts are preferred in the case of high in situ stresses.A natural pressure arch is formed in the rock at a certain distance behind the tunnel *** should be long enough to reach the natural pressure arch when the failure zone is *** bolt length should be at least 1 m beyond the failure *** the case of a vast failure zone,tightly spaced short rockbolts are installed to establish an artificial pressure arch within the failure zone and long cables are anchored on the natural pressure *** this case,the rockbolts are usually less than 3 m long in mine drifts,but can be up to 7 m in large-scale rock *** spacing is more important than bolt length in the case of establishing an artificial pressure *** addition to the factor of safety,the maximum allowable displacement in the tunnel and the ultimate displacement capacity of rockbolts must be also taken into account in the ***,rockbolts should be compatible with other support elements in the same support system in terms of displacement and energy absorption capacities.

关键词： Rockbolting design Pressure arch Bolt length Bolt spacing Factor of safety

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Geochemical characteristics of the coal gangues from the Du'erping coal mine, Xishan coalfield, North China

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Chinese Journal Of Geochemistry 2013年第2期32卷 227-234页

作者： WEN Xueqin ZENG Fangui ZHANG Hong department of geoscience and Technology School of Mining Technology Taiyuan University of Technology

Inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectroscopy, hydride generation-atomic fluorescence spectrometry, emission spectrometry, X fluorescence spectrometry, and X-ray diffraction were employed to study the geochemistry and mineralogy of coal gangues from Nos. 2, 3, and 8 coal seams of the Du'erping coal mine, Xishan coalfield, Taiyuan, Shanxi Province. The study revealed that compared with the sedimentary cover, upper continent crust, Carboniferous-Permian coal from North China, as well as most coal in China, coal gangues from Nos. 2 and 3 coal seams are rich in Li, Be, Sc, Cr, Cu, Ga, Ba, Th, Nb, Cd, Pb, Ta and rare-earth elements, and coal gangues from No. 8 coal seam are rich in Li, Sc, V, Cr, Ga, U, and rare-earth elements. Compared with the Carboniferous-Permian coal from North China and most coal in China, coal gangues from Nos. 2, 3 and 8 seams are rich in Rb, V, Cs and Sr. Therefore, The Du'erping coal gangues in the Xishan coalfield are rich in most hazardous trace elements and rare-earth elements, wherein the contents of Ga and Li reach the industrial grade and have significance for industrial utilization. On the whole, coal gangues of the Shanxi Formation from the Permian are rich in more trace elements than those of the Carboniferous Taiyuan Formation. The distributions of REE show obviously dipping rightwards with negative Eu anomalies. The contents of rare-earth elements in the three seams are quite different. All of the above indicate that the source of the rare-earth elements is terrigenous debris. Minerals in No. 2 seam identified by X-ray diffraction mainly include quartz, kaolinite, in addition to calcite, pyrite, apatite, epidote, and epsomite. No. 3 seam mainly contains quartz, kaolinite, in addition to a small amount of sodium feldspar, calcium nitrate, iron ore, gypsum, and vivianite. No. 8 seam mainly contains kaolinite, dickite, quartz, illite, and a small amount of hematite and U. The corr

关键词：地球化学特征中国北方西山煤田煤矸石电感耦合等离子体质谱煤矿稀土元素原子荧光光谱

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Blueschist from the Toudaoqiao Area, Inner Mongolia, NE China: Evidence for the Suture between the Ergun and the Xing'an Blocks

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Journal of Earth Science 2017年第2期28卷 241-248页

作者： Limin Zhao Akira Takasu Yongjiang Liu Weimin Li College of Earth Sciences Jilin University department of geoscience Shimane University

Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemistry. The amphiboles in the blueschist are zoned from winchite core to magnesioriebeckite/glaucophane rim to winchite outermost rim. The peak metamorphic conditions are defined by the mineral assemblage of magnesioriebeckite/glaucophane, epidote, high-Si phengite（Si〈7.1）, chlorite, albite, hematite and quartz, indicating an epidote-blueschist facies metamorphism. The P-T conditions are estimated as T=350–400 ℃ and P=10-12 kbar. The occurrence of the blueschist along the Xinlin-Xiguitu fault strongly suggests the fault is the suture between the Ergun and the Xing＇an blocks situated in the eastern portions of the Central Asia Orogenic Belt（CAOB）.

关键词： Toudaoqiao blueschists zoned amphibole P-T path Xinlin-Xiguitu suture

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