REE and Sr isotope characteristics of carbonate within the Cu–Co mineralized sedimentary sequence of the Nchanga Mine,Zambian Copperbelt     

Stephen Roberts  Martin R. Palmer  Matthew J. Cooper  Peter Buchaus  Drew Sargent 《Mineralium Deposita》2009,44(8):881-891

Carbonate, largely in the form of dolomite, is found throughout the host rocks and ores of the Nchanga mine of the Zambian Copperbelt. Dolomite samples from the hanging wall of the mineralization show low concentrations of rare-earth elements (REE) and roof-shaped, upward convex, shale-normalized REE patterns, with positive Eu*_SN anomalies (1.54 and 1.39) and marginally negative Ce anomalies (Ce*_SN 0.98,0.93). In contrast, dolomite samples associated with copper and cobalt mineralization show a significant rotation of the REE profile, with HREE enrichment, and La/Lu_SN ratios <1 (0.06–0.42). These samples also tend to show variable but predominantly negative Eu*_SN and positive cerium anomalies and an upwardly concave MREE distribution (Gd-Er). Malachite samples from the Lower Orebody show roof-tile-normalized REE patterns with negative europium anomalies (Eu*_SN 0.65–0.80) and negative cerium anomalies (Ce*_SN 0.86–0.9). The carbonate ⁸⁷Sr/⁸⁶Sr signature correlates with the associated REE values. The uppermost dolomite samples show Neoproterozoic seawater-like ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7111 to 0.7116, whereas carbonate from Cu–Co mineralized samples show relatively low concentrations of strontium and more radiogenic ⁸⁷Sr/⁸⁶Sr, ranging between 0.7136–0.7469. The malachite samples show low concentrations of strontium, but give a highly radiogenic ⁸⁷Sr/⁸⁶Sr of 0.7735, the most radiogenic ⁸⁷Sr/⁸⁶Sr ratio. These new data suggest that the origin and timing of carbonate precipitation at Nchanga is reflected in the REE and Sr isotope chemistry. The upper dolomite samples show a modified, but essentially seawater-like signature, whereas the rotation of the REE profile, the MREE enrichment, the development of a negative Eu*_SN anomaly and more radiogenic ⁸⁷Sr/⁸⁶Sr suggests the dolomite in the Cu–Co mineralized samples precipitated from basinal brines which had undergone significant fluid–rock interaction. Petrographic, REE, and ⁸⁷Sr/⁸⁶Sr data for malachite are consistent with the original sulfide Lower Orebody being subject to a later oxidizing event.  相似文献   

Uncovering Influences on the Form of Oil and Gas Field Size Distributions     

Schuenemeyer  John H.  Drew  Lawrence J. 《Natural Resources Research》1999,8(1):37-47

A detailed understanding of the processes that led to empirical oil and gas field size distributions, especially the dynamic character of the discovery process, is needed to improve the quality of forecasts of oil and gas resources. An empirical distribution results from a complex interaction of economic, technical, and social factors with geology in the form of a distribution of deposits. These factors may cause an empirical distribution to mutate nonrandomly through time. Changes in the price of oil, the cost of exploration and development, technology, and access to prospects influence the discovery process. Failure to recognize and account for them in the modeling process can result in serious bias in estimates of the number and volume of future discoveries. In addition, the broad range of some forecasts for a given region may be explained by differences in perspective of those involved in the process. Geologists who understand the basic processes and collect the data may be scientific determinists. Statisticians who model and analyze the data are trained to think in terms of random variables and stochastic processes.  相似文献   

Directions     

Drew  Lawrence J. 《Natural Resources Research》1994,3(4):253-256

Natural Resources Research -  相似文献   

Directions     

Lawrence J. Drew 《Natural Resources Research》1994,3(3):167-168

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Effects of Olestra on Organic and Solids Removal in Septic Tanks     

Drew C. McAvoy  Jacqueline A. Greff  D. Ronald Webb  Greg S. Allgood 《Ground Water Monitoring & Remediation》1998,18(4):131-138

A field study was conducted to examine the fate and potential effects of olestra, a non-caloric fat replacer, in septic tanks. The study compared the performance of parallel septic tanks, which were led domestic waste water with liquid and solid forms of olestra, against a control tank receiving waste water without olestra. Results showed that 36 g/d of olestra dosed to the tanks (a three-fold exaggeration of expected loadings) had no adverse effect on system operation (based on visual observations and sludge accumulation) or performance (based on removal of organic content and solids) over a six-month period. Removal efficiencies for total suspended solids (TSS), carbonaceous biochemical oxygen demand (CBOD), and chemical oxygen demand (COD) were not significantly different (p<0.05) in the olestra tanks when compared to the control tank. In addition, a relatively small amount of the total olestra added (3 to 6%) was recovered in the septic tank effluents over the course of the study. Accumulation of tank solids was not affected as measured sludge levels in the tank at the middle and end of the study showed no difference between the olestra dosed tanks and the control tank.  相似文献   

The times     

Lawrence J. Drew 《Natural Resources Research》1998,7(2):89-91

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A radiation-driven disc wind model for massive young stellar objects     

Janet E. Drew  Daniel Proga  & James M. Stone 《Monthly notices of the Royal Astronomical Society》1998,296(1):L6-L10

The generation of magnetic fields by a battery, operating in an ion–electron plasma around a Kerr black hole, is studied in the 3+1 split of the Kerr metric. It is found that the gravitomagnetic contributions to the electron partial pressure are able to drive currents. The strength of the equilibrium magnetic field should be higher than for the classical Biermann battery, which is found to operate in this relativistic context as well, since the gravitomagnetic driving terms can less easily be quenched than the classical ones. In axisymmetry the battery can induce only toroidal magnetic fields. Once a toroidal magnetic field is present, however, the coupling of gravitomagnetic and electromagnetic fields generates a poloidal magnetic field even in axisymmetry. A rotating black hole, embedded in plasma, will therefore always generate toroidal and poloidal magnetic fields.  相似文献   

Physiology of Laminaria     

Nichola J.  Conolly Edward A.  Drew 《Marine Ecology》1985,6(3):181-195

Abstract. Dissolved nitrate, nitrite, ammonium and phosphate were monitored for 2.5 years along a coastal eutrophication gradient originating at the St. Andrews sewer outfall. Linear growth rates and tissue composition (phosphorus, various nitrogen fractions and storage carbohydrates) were monitored at the same stations in lamina tissue of Laminaria digitata and L. saccharina. Growth rates were considerably enhanced at the eutrophicated stations both in spring, when exogenous nutrients were at peak values at all stations, and during the summer when exogenous nutrients were very low at all stations. Enhanced summer growth rates were correlated with the increased reserves of N and P accumulated during winter and spring, and particularly with soluble organic nitrogen reserves. Accumulation of storage carbohydrates was inversely correlated with growth rate and tissue N and P reserves, presumably because fixed carbon could be incorporated into new protein and thence new tissue only if internal non-protein N reserves were available.  相似文献   

High resolution observations of the radio emission from luminous YSOs     

M. G. Hoare  J. E. Drew  S. T. Garrington  M. J. McCaughrean 《Astrophysics and Space Science》1995,224(1-2):483-484

New, high-resolution 1.66 GHz MERLIN maps of Cep A2 and LkH101 are presented and discussed.  相似文献   

The space-time structure of oil and gas field growth in a complex depositional system     

Lawrence J. Drew  Richard F. Mast  John H. Schuenemeyer 《Natural Resources Research》1994,3(3):169-182

Shortly after the discovery of an oil and gas field, an initial estimate is usually made of the ultimate recovery of the field. With the passage of time, this initial estimate is almost always revised upward. The phenomenon of the growth of the expected ultimate recovery of a field, which is known as field growth, is important to resource assessment analysts for several reasons. First, field growth is the source of a large part of future additions to the inventory of proved reserves of crude oil and natural gas in most petroliferous areas of the world. Second, field growth introduces a large negative bias in the forecast of the future rates of discovery of oil and gas fields made by discovery process models. In this study, the growth in estimated ultimate recovery of oil and gas in fields made up of sandstone reservoirs formed in a complex depositional environment (Frio strand plain exploration play) is examined. The results presented here show how the growth of oil and gas fields is tied directly to the architectural element of the shoreline processes and tectonics that caused the deposition of the individual sand bodies hosting the producible hydrocarbon.  相似文献