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metamorphic consequences of secular changes in oceanic crust composition and implications for uniformitarianism in the geological record

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Geoscience Frontiers 2018年第4期9卷 1009-1019页

作者： richard m.palin Brendan Dyck Department of Geology and Geological Engineering Colorado School of Mines Department of Earth Sciences Simon Fraser University

Cooling of the Earth＇s mantle since the meso-Archean is predicted by thermal and petrological models to have induced a secular change in the composition of primary mantle-derived magmas-and thus bulk oceanic crust; in particular, suggesting a decrease in maficity over time. This hypothesis underpins several recent studies that have addressed key geological questions concerning evolving plate tectonic styles, the rates and timing of continental crust formation, comparative planetology, and the emergence of complex life on Earth. major, minor, and trace element geochemical analyses of（meta）mafic rocks preserved in the geological record allows exploration of this theory, although no consensus currently exists about the magnitude of this change and what compositions-if anything-constitute representative examples of Paleo-, meso-, or Neo-Archean primitive oceanic crust. In this work, we review the current state of understanding of this issue, and use phase equilibria to examine the different mineral assemblages and rock types that would form during metamorphism of basalt of varying maficity in subduction zone environments. The presence（or absence） of such metamorphic products in the geological record is often used as evidence for（or against） the operation of modern-day subductiondriven plate tectonics on Earth at particular time periods; however, the control that secular changes in composition have on the stability of mineral assemblages diagnostic of subduction-zone metamorphism weakens such uniformitarianistic approaches. Geodynamic interpretations of the Archean metamorphic rock record must therefore employ a different set of petrological criteria for determining tectonothermal histories than those applied to Proterozoic or Phanerozoic equivalents.

关键词： Archean mantle cooling Oceanic crust Basalt metamorphism Uniformitarianism

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metamorphism at convergent plate margins:Preface

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Geoscience Frontiers 2022年第2期13卷 351-353页

作者： richard m.palin Nick m.W.Roberts Department of Earth Sciences University of OxfordOxford OX13ANUnited Kingdom Geochronology and Tracers Facility British Geological SurveyEnvironmental Science CentreNottinghamUnited Kingdom

*** The year 2020 will long be recognised as a period of sadness and frustration for academics worldwide,given the catastrophic impact that the spread of novel coronavirus“2019-nCoV”-or COVID-19-has had on research and teaching activities,as well as in their personal *** Special Issue was designed to represent an avenue for dissemination of many studies presented at the September2019 Geological Society of America session T23.

关键词： teaching America has

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Secular change in earth processes： Preface

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Geoscience Frontiers 2018年第4期9卷 965-966页

作者： richard m.palin Christopher J.Spencer Department of Geology and Geological Engineering Colorado School of Mines Golden CO 80401 USA The Institute of Geoscience Research (TIGER) School of Earth and Planetary Sciences Curtin University WA 6102 Australia

*** Uniformitarianism is a traditional approach used in many areas of geoscience that assumes the geologic processes observed today operated similarly throughout all of Earth history（Hutton,1788;Windley,1993）,with such an ideology commonly encapsulated by the maxim＂the present is the key to the past＂.This concept is closely associated with the philosophical principle of Occam’s razor.

关键词： Secular change in earth processes Preface

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Quantifying geological uncertainty in metamorphic phase equilibria modelling;a monte Carlo assessment and implications for tectonic interpretations

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Geoscience Frontiers 2016年第4期7卷 591-607页

作者： richard m.palin Owen m.Weller David J.Waters Brendan Dyck Institute of Geosciences Johannes-Gutenberg University Mainz55128MainzGermany Geological Survey of Canada 601 Booth StreetOttawaONKIA OESCanada Department of Earth Sciences University of OxfordOxfordOX1 3ANUnited Kingdom

Pseudosection modelling is rapidly becoming an essential part of a petrologist＇s toolkit and often forms the basis of interpreting the tectonothermal evolution of a rock sample, outcrop, or geological region. Of the several factors that can affect the accuracy and precision of such calculated phase diagrams, ＂geological＂ uncertainty related to natural petrographic variation at the hand sample- and/or thin section-scale is rarely considered. Such uncertainty influences the sample＇s bulk composition, which is the primary control on its equilibrium phase relationships and thus the interpreted pressure-temper- ature （P-T） conditions of formation. Two case study examples--a garnet-cordierite granofels and a garnet-staurolite-kyanite schist--are used to compare the relative importance that geological uncer- tainty has on bulk compositions determined via （1） X-ray fluorescence （XRF） or （2） point counting techniques. We show that only minor mineralogical variation at the thin-section scale propagates through the phase equilibria modelling procedure and affects the absolute P-T conditions at which key assemblages are stable. Absolute displacements of equilibria can approach ＋l kbar for only a moderate degree of modal proportion uncertainty, thus being essentially similar to the magnitudes reported for analytical uncertainties in conventional thermobarometry. Bulk compositions determined from multiple thin sections of a heterogeneous garnet-staurolite-kyanite schist show a wide range in major-element oxides, owing to notable variation in mineral proportions. Pseudosections constructed for individual point count-derived bulks accurately reproduce this variability on a case-by-case basis, though averaged proportions do not correlate with those calculated at equivalent peak P-T conditions for a whole-rock XRF-derived bulk composition. The main discrepancies relate to varying proportions of matrix phases （primarily mica） relative to porphyroblasts （primarily staurolite and kyanit

关键词： Geological uncertainty Error Pseudosection monte Carlo mnNCKFmASHTO

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mafic Archean continental crust prohibited exhumation of orogenic UHP eclogite

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Geoscience Frontiers 2021年第5期12卷 411-420页

作者： richard m.palin James D.P.moore Zeming Zhang Guangyu Huang Jon Wade Brendan Dyck Department of Earth Sciences University of OxfordOxford OX13ANUnited Kingdom Earth Observatory of Singapore Nanyang Technological UniversitySingapore Institute of Geophysics SGEESVictoria University of WellingtonWellingtonNew Zealand Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Department of Earth Environmental and Geographical SciencesUniversity of British ColumbiaKelowna V1V 1V7Canada

The absence of ultrahigh pressure(UHP)orogenic eclogite in the geological record older than c.0.6 Ga is problematic for evidence of subduction having begun on Earth during the Archean(4.0-2.5 Ga).many eclogites in Phanerozoic and Proterozoic terranes occur as mafic boudins encased within low-density felsic crust,which provides positive buoyancy during subduction;however,recent geochemical proxy analysis shows that Archean continental crust was more mafic than previously thought,having greater proportions of basalt and komatiite than modern-day ***,we show via petrological modelling that secular change in the petrology and bulk composition of upper continental crust would make Archean continental terranes negatively buoyant in the mantle before reaching UHP *** or delaminated Archean continental crust passes a point of no return during metamorphism in the mantle prior to the stabilization of coesite,while Proterozoic and Phanerozoic terranes remain positively buoyant at these *** orogenic eclogite may thus readily have formed on the Archean Earth,but could not have been exhumed,weakening arguments for a Neoproterozoic onset of subduction and plate ***,isostatic balance calculations for more mafic Archean continents indicate that the early Earth was covered by a global ocean over 1 km deep,corroborating independent isotopic evidence for large-scale emergence of the continents no earlier than c.3 *** findings thus weaken arguments that early life on Earth likely emerged in shallow subaerial ponds,and instead support hypotheses involving development at hydrothermal vents in the deep ocean.

关键词： Archean Eclogite Exhumation Secular change Geodynamics Density

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Understanding Science Through the Computational Lens

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Journal of Computer Science & Technology 2011年第4期26卷 569-577页

作者： richard m.Karp Department of Electrical Engineering and Computer Sciences University of California

This article explores the changing nature of the interaction between computer science and the natural and social sciences. After briefly tracing the history of scientific computation, the article presents the concept of computational lens, a metaphor for a new relationship that is emerging between the world of computation and the world of the sciences. Our main thesis is that, in many scientific fields, the processes being studied can be viewed as computational in nature, in the sense that the processes perform dynamic transformations on information represented as digital data. Viewing natural or engineered systems through the lens of their computational requirements or capabilities provides new insights and ways of thinking. A number of examples are discussed in support of this thesis. The examples are from various fields, including quantum computing, statistical physics, the World Wide Web and the Internet, mathematics, and computational molecular biology.

关键词： computational process computer science and other sciences computational lens

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What we have learned from randomized trials of prostate cancer screening

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Asian Journal of Andrology 2011年第3期13卷 369-373,510页

作者： richard m Hoffman Anthony Y Smith medicine Service New Mexico VA Health Care System Albuquerque NM 87108 USA Department of medicine University of New Mexico School of Medicine Albuquerque NM 87108 USA Department of Surgery University of New Mexico School of Medicine Albuquerque NM 87108 USA

The introduction of prostate-specific antigen （PSA） for prostate cancer screening in the late 1980s led to an epidemic of prostate cancer, particularly in developed countries. However, the first valid reports from randomized controlled trials on the efficacy of screening were not published until 2009. men in the screening group in the European Randomized Study of Screening for Prostate Cancer were 20% less likely than those in the control group to die from prostate cancer. The absolute difference was only 0.7/1000, implying that over 1400 men needed to be screened to prevent one prostate cancer death. Screening was also associated with a 70% increased risk for being diagnosed with prostate cancer. The American Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial found no survival benefit for screening. Results were not conclusive because a substantial proportion of study subjects had previously undergone PSA testing, over half of the control group had PSA testing, follow-up was relatively short, and fewer than 100 subjects died from prostate cancer. Balancing the potential survival benefit from screening is the risk of overdiagnosis--finding cancers that would not otherwise cause clinical problems^and the risk of treatment complications, including urinary, sexual and bowel dysfunction. Prostate cancer screening efforts would benefit from improved biomarkers, which more readily identify clinically important cancers. Cancer control efforts might also need to include chemoprevention, though currently available agents are controversial. In the meantime, oatients need to be supoorted in achievine informed decisions on whether to be screened for orostate cancer.

关键词： cancer screening prostate-specific antigen prostatic neoplasms randomized controlled trials as topic

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Seismic performance of steel mRF building with nonlinear viscous dampers

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Frontiers of Structural and Civil Engineering 2016年第3期10卷 254-271页

作者： Baiping DONG James m. RICLES richard SAUSE ATLSS Engineering Research Center Department of Civil and Environmental Engineering Lehigh University Bethlehem PA 18015 USA

This paper presents an experimental study of the seismic response of a 0.6-scale three-story seismicresistant building structure consisting of a moment resisting frame （mRF） with reduced beam sections （RBS）, and a frame with nonlinear viscous dampers and associated bracing （called the DBF）. The emphasis is on assessing the seismic performance for the design basis earthquake （DBE） and maximum considered earthquake （mCE）. Three mRF designs were studied, with the mRF designed for 100%, 75%, and 60%, respectively, of the required base shear design strength determined according to ASCE 7-10. The DBF with nonlinear viscous dampers was designed to control the lateral drift demands. Earthquake simulations using ensembles of DBE and mCE ground motions were conducted using the real-time hybrid simulation method. The results show the drift demand and damage that occurs in the mRF under seismic loading. Overall, the results show that a high level of seismic performance can be achieved under DBE and mCE ground motions, even for a building structure designed for as little as 60% of the base shear design strength required by ASCE 7-10 for a structure without dampers.

关键词： seismic response steel mRF nonlinear viscous damper design basis earthquake real-time hybrid simulation

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The dilemma of the Jiaodong gold deposits: Are they unique?

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Geoscience Frontiers 2014年第2期5卷 139-153页

作者： richard J.Goldfarb m.Santosh U.S.Geological Survey Box 25046 MS 973 Denver Federal Center State Key Laboratory of Geological Processes and mineral Resources School of Earth Sciences and Resources China University of Geosciences Centre for Exploration Targeting School of Earth and Geographical Sciences University of Western Australia Crawley

The ca. 126e120 ma Au deposits of the Jiaodong Peninsula, eastern China, define the country＇s largest gold province with an overall endowment estimated as＆gt;3000 t Au. The vein and disseminated ores are hosted by NE-to NNE-trending brittle normal faults that parallel the margins of ca. 165e150 ma, deeply emplaced, lower crustal melt granites. The deposits are sited along the faults for many tens of kilometers and the larger orebodies are associated with dilatational jogs. Country rocks to the granites are Pre-cambrian high-grade metamorphic rocks located on both sides of a Triassic suture between the North and South China blocks. During early mesozoic convergent deformation, the ore-hosting structures developed as ductile thrust faults that were subsequently reactivated during Early Cretaceous ＂Yan-shanian＂intracontinental extensional deformation and associated gold formation. 〈br〉 Classification of the gold deposits remains problematic. many features resemble those typical of orogenic Au including the linear structural distribution of the deposits, mineralization style, ore and alteration assemblages, and ore fluid chemistry. However, Phanerozoic orogenic Au deposits are formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens. The Jiaodong de-posits, in contrast, formed within two Precambrian blocks approximately 2 billion years after devolati-lization of the country rocks, and thus require a model that involves alternative fluid and metal sources for the ores. A widespread suite of ca. 130e123 ma granodiorites overlaps temporally with the ores, but shows a poor spatial association with the deposits. Furthermore, the deposit distribution and mineral-ization style is atypical of ores formed from nearby magmas. The ore concentration requires fluid focusing during some type of sub-crustal thermal event, which could be broadly related to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific plate subducti

关键词： Gold Jiaodong North China block Tectonics mineral deposit mode

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Biochar and Compost Increase Crop Yields but the Effect is Short Term on Sandplain Soils of Western Australia

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Pedosphere 2015年第5期25卷 720-728页

作者： David J.m.HALL richard W.BELL Department of Agriculture and Food School of Veterinary and Life Sciences Murdoch University

Sandplain soils on the south coast of Western Australia have low inherent fertility, which is mainly due to poor nutrient retention caused by insufficient clay and organic colloidal material. Previous research has shown the benefits in nutrient levels and retention from adding clay to sandplain soils; however, there is almost no information on the addition of organic amendments. A field experiment was established at the Esperance Downs Research Station, Western Australian, in may 2010, to assess the effects of wheat straw(WS) and chicken manure(Cm) biochars and compost with and without phosphorus(P) addition on soil properties and crop production over five growing seasons. The five seasons alternated between winter and summer crops. The Cm and WS biochar and compost treatments significantly increased crop yields and P uptake in 3, 2 and 1 of the five seasons, respectively. The yield increases(P more than 8%. By the end of the third season, no differences in crop yields were found that could be attributed to the organic amendments. The addition of P increased crop yields in each winter cropping season. Phosphorus addition explained more than 30%of the variation in crop yields. Despite marginal P levels and summer drought conditions, arbuscular mycorrhizal root colonisation was not affected by the organic amendments. There were no significant interactions between the organic amendments and P addition in terms of crop yields, P uptake or P uptake efficiency. We conclude that much of the effect of the organic amendments was due to direct nutrient addition which dissipated over time.

关键词： mycorrhizal root colonisation nutrient retention organic amendments P addition P uptake

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