Letšeng diamond mine,Lesotho: a variant of Kimberley-type pyroclastic kimberlite emplacement     

Hetman  Casey M.  Scott Smith  Barbara  Robey  Jock  Nkotsi  Teboho  Mohapi  Mohapi  Mohapi  Thabang 《Mineralogy and Petrology》2018,112(2):365-382

The Letšeng Diamond Mine comprises two ~91 Ma kimberlite pipes. An update of the geology is presented based on the 2012–2017 detailed investigation of open pit exposures and all available drillcores which included mapping, logging and petrography. Each of the steep-sided volcanic pipes comprises a number of phases of kimberlite with contrasting diamond contents which were formed by the emplacement of at least four batches of mantle-derived magma. The resulting range of textures includes resedimented volcaniclastic kimberlite (RVK), Kimberley-type pyroclastic kimberlite (KPK), coherent kimberlite (CK) and minor amounts of hypabyssal kimberlite (HK). The pipes are compared with KPK occurrences from southern Africa and worldwide. Many features of the Letšeng pipes are similar to KPK infilled pipes particularly those of the widespread Cretaceous kimberlite province of southern Africa. The differences displayed at Letšeng compared to other large KPK pipe infills described from around the world are attributed to the marginal or melnoitic nature of the magma and the upper diatreme to crater setting of the Letšeng pipes, where processes become extrusive. It is concluded that the pipes comprise a variant of Kimberley-type pyroclastic kimberlite emplacement. The classification of many of the Letšeng rocks as KPK is important for developing the internal geology of the pipes as well as for predicting the distribution of diamonds within the bodies.

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A Palaeoenvironmental Investigation of Two Prehistoric Burnt Mound Sites in Northern Ireland     

J. Wheeler  S. Timpany  T. M. Mighall  L. Scott 《Geoarchaeology》2016,31(6):506-529

This paper provides a summary of the palaeoenvironmental evidence from a spread of late Mesolithic burnt material and two late Neolithic to early Bronze Age burnt mounds. The burnt mounds were up to 10 m diameter, had an amorphous shape, and were consistently less than 0.8 m thick. Monoliths were collected from two sites, Ballygawley and Roughan, in Co. Tyrone, Northern Ireland. This provided an opportunity to use a detailed palaeoecological approach for the first time to investigate the use and function of burnt mounds. Pollen, non‐pollen palynomorphs, micro‐ and macroscopic charcoal were used to place these features within their environmental context, and to establish if such an approach could provide further insights into their function. The palynological results shared similar characteristics: high microscopic charcoal values, repetitive fluctuations in tree and shrub taxa, increased Sphagnum, and the presence of non‐pollen palynomorphs (NPPs) HdV‐114 and HdV‐146, all of which could be diagnostic indicators of burnt mounds in palynological records. While the data do not allow us to ascribe a specific function for the burnt mounds, their environmental setting is discussed. A “see‐saw” pattern of arboreal pollen, combined with the macroscopic charcoal data, indicate possible species selection and management of local woodland for fuelwood.  相似文献   

Joseph I. Goldstein (1939–2015)          下载免费PDF全文

Edward R.D. Scott 《Meteoritics & planetary science》2016,51(2):438-440

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Biot consolidation analysis with automatic time stepping and error control Part 1: theory and implementation     

Scott W. Sloan  Andrew J. Abbo 《国际地质力学数值与分析法杂志》1999,23(6):467-492

A new finite element algorithm for solving elastic and elastoplastic coupled consolidation problems is described. The procedure treats the governing consolidation relations as a system of first-order differential equations and is based on the backward Euler and Thomas and Gladwell schemes with automatic subincrementation of a prescribed series of time increments. The prescribed time increments, which are called coarse time steps, serve to start the procedure and are chosen by the user. The automatic consolidation algorithm attempts to select the time subincrements such that, for a given mesh, the time-stepping (or temporal discretisation) error in the displacements lies close to a specified tolerance. Unlike existing solution techniques, the new algorithm computes not only the displacements and pore pressures, but also their derivatives with respect to time. These extra variables permit a family of unconditionally stable integration algorithms to be constructed which automatically provide an estimate of the local truncation error for each time step. This error estimate is inexpensive to compute and may be used to develop a simple and efficient automatic time stepping mechanism. For the elastic case, the displacements and pore pressures at the end of each subincrement may be solved directly without the need for iteration. For elastoplastic behaviour, however, the governing relationships are non-linear and a system of non-linear equations must be solved to compute the updates. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

The legal context of intellectual property rights and marine biotechnology     

Geoffrey R. Scott 《Ocean & Coastal Management》1998,38(3):229-277

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Shakedown analysis of ballasted track structure using three-dimensional finite element techniques     

Wang  Kangyu  Zhuang  Yan  Kouretzis  George  Sloan  Scott William 《Acta Geotechnica》2020,15(5):1231-1241

Acta Geotechnica - Shakedown analysis is an attractive method for determining the capacity of geostructures to sustain repeated loads involving a large number of cycles, e.g. rolling and sliding...  相似文献   

Near-infrared adaptive optics imaging of nuclear spiral structure in the Seyfert galaxy NGC 3227     

Scott C. Chapman  †‡  Simon L. Morris ‡  Gordon A. H. Walker 《Monthly notices of the Royal Astronomical Society》2000,319(3):666-676

We present high spatial resolution, near-infrared images in J , H and K of the nucleus of NGC 3227, obtained with the Adaptive Optics Bonnette on the Canada–France–Hawaii Telescope. The ∼0.15 arcsec (17 pc) resolution allows structures to be probed in the core region. Dust obscuration becomes significantly less pronounced at longer wavelengths, revealing the true geometry of the core region. We are able to identify two main features in our maps: (i) a spiralling association of knots with a counterpart in a Hubble Space Telescope F606W image; and (ii) a smaller-scale annulus, orthogonal to the spiral of knots. These features may provide a means to transport material inwards to fuel the active nucleus.  相似文献   

The solar occultation for ice experiment     

Larry L. Gordley  Mark E. Hervig  Chad Fish  James M. Russell  Scott Bailey  James Cook  Scott Hansen  Andrew Shumway  Greg Paxton  Lance Deaver  Tom Marshall  John Burton  Brian Magill  Chris Brown  Earl Thompson  John Kemp 《Journal of Atmospheric and Solar》2009,71(3-4):300-315

The Solar Occultation For Ice Experiment (SOFIE) was launched onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite on 25 April 2007, and began science observations on 14 May 2007. SOFIE conducts solar occultation measurements in 16 spectral bands that are used to retrieve vertical profiles of temperature, O₃, H₂O, CO₂, CH₄, NO, and polar mesospheric cloud (PMC) extinction at wavelengths from 0.330 to 5.006 μm. SOFIE performs 15 sunset measurements at latitudes from 65° to 85°S and 15 sunrise measurements from 65° to 85°N each day. This work describes the SOFIE instrument, measurement approach, and retrieval results for the northern summer of 2007.  相似文献   

Hydroclimatic and channel snowpack controls over suspended sediment and grain size transport in a High Arctic catchment     

Dana M. McDonald  Scott F. Lamoureux 《地球表面变化过程与地形》2009,34(3):424-436

Temporal variability in suspended sediment delivery processes was studied during three seasons in a 7·9 km² catchment at Cape Bounty, Melville Island, Nunavut in the Canadian High Arctic. Discharge was controlled primarily by the magnitude of snowmelt, with limited inputs from ground ice melt and precipitation. Years with greater snowpack non‐linearly increased sediment yield and resulted in seasonal counter‐clockwise hysteresis, while a year with low snowpack resulted in reduced sediment yield and clockwise hysteresis, and indicates that sediment was increasingly available after the onset of streamflow. In addition to the event‐scale hysteresis observed during the nival discharge peak, diurnal clockwise hysteresis was observed during all three seasons and suggests daily exhaustion of sediment supplies. These results indicate that the channel snowpack plays a primary role over sediment accessibility during the nival discharge peak. Similarly, grain size analysis of suspended material in the river showed that the coarsest mean grain size was transported during the early phase of peak nival discharge and indicates that isolated sources of coarse material were being accessed by high velocity flow. Snowpack is present through the peak nival period and conditions sediment availability by isolating channel sediments from high‐energy flow. These results indicate sediment delivery characteristics in small High Arctic catchments reflect complex interactions with channel snowpack and disproportionate responses to flow conditions that differ from glacial and temperate settings. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Response to “Limitations in the Hilbert Transform Approach to Locating Solar Cycle Terminators” by R. Booth     

Leamon  Robert J.  McIntosh  Scott W.  Chapman  Sandra C.  Watkins  Nicholas W. 《Solar physics》2021,296(10):1-18

Solar Physics - The Maunder Minimum (1645?–?1715) was unique in terms of solar-cycle amplitudes and sunspot-position distributions registered in the last four centuries; however,...  相似文献