The genesis of sediment-hosted,exhalative zinc + lead deposits   总被引：2，自引：0，他引：2  

M. J. Russell  M. Solomon  J. L. Walshe 《Mineralium Deposita》1981,16(1):113-127

Large sediment-hosted lead+zinc deposits like Mount Isa, McArthur River, Navan, Rammelsberg and Sullivan form a distinctive group characterised by stratiform, syngenetic sulphide ores that formed in local basins on the sea floor as a result of protracted hydrothermal activity accompanying continental rifting. Generally there is a development of a sedimentary pre-ore phase mineralization often featuring manganese followed by zinc±lead, iron and chert. Lower main phase zinc+lead lenses are usually almost devoid of copper but Cu tenors increase toward the middle or top of the ore sequences. Hanging wall trace element haloes are common. These characteristics are accounted for by deriving the ore solutions from subsurface convective circulation of modified highly saline seawater. The circulation is initiated during rifting and driven by a high geothermal gradient. As a result of continued extensional strain and cooling of the rock column the brittle-to-ductile transition zone is depressed and the circulation penetrates to greater depth with time. Of the ore metals the downward-penetrating convection fluids first leach and transport zinc and lead, but with increasing temperature are later able to leach and transport some copper. Unless convective circulation ceases the metal sequence generally reverses as the cooling phase sets in. The minimum distance separating major coeval orebodies of this type is 18 km which is a function of the size of the convective systems.  相似文献   

Silurian Sedimentation in the South Qilian Belt: Arc-Continent Collision-related Deposition in the NE Tibet Plateau?     

YAN Zhen  FU Changlei  Jonathan C. AITCHISON  ZHOU Renjie  Solomon BUCKMAN  CHEN Lei 《《地质学报》英文版》2020,94(4):901-913

The South Qilian belt mainly comprises an early Paleozoic arc-ophiolite complex, accretionary prism, microcontinental block, and foreland basin. These elements represent accretion-collision during Cambrian to Silurian time in response to closure of the Proto-Tethyan Ocean in the NE of the present-day Tibet Plateau. Closure of the Proto-Tethyan Ocean between the Central Qilian block and the Oulongbuluke block and the associated collision took place from NE to SW in a zipper-like style. Sediment would have been dispersed longitudinally SW-ward with a progressive facies migration from marginal alluvial sediments toward slope deep-water and deep-sea turbidites. This migration path indicates an ocean basin that shrank toward the SW. The Balonggongga'er Formation in the western South Qilian belt represents the fill of a latest Ordovician-Silurian remnant ocean basin that separated the Oulongbuluke block from the Central Qilian block, and records Silurian closure of the Proto-Tethyan Ocean and subduction beneath the Central Qilian block. However, alluvial deposits in the Lajishan area were accumulated in a retro-foreland basin, indicating that continent-continent collision in the eastern South Qilian belt occurred at c. 450–440 Ma. These results demonstrate that the Proto-Tethyan Ocean closed diachronously during early Paleozoic time.  相似文献   

Biogenic hydrocarbons in fluid inclusions from the aberfoyle tin-tungsten deposit, Tasmania, Australia   总被引：3，自引：0，他引：3  

C. F. Hoffmann  R. W. Henley  N. C. Higgins  M. Solomon  R. E. Summons 《Chemical Geology》1988,70(4):287-299

Trace components in fluid inclusions from the Aberfoyle tin-tungsten deposit in Tasmania, Australia, were examined by thermal decrepitation-mass spectrometry. The technique involves the decrepitation of fluid inclusions by stepwise heating in the source of a mass spectrometer. In addition to water, other species identified were carbon dioxide and hydrocarbons. Detailed analysis of these hydrocarbons showed that they ranged in carbon number from C₁ up to at least C₃₃ and probably comprised, in part, biological marker compounds, previously unreported in such high-temperature environments. Their presence suggests that the fluid responsible for mineralisation was not entirely magmatic but contained a non-magmatic component evolved through fluid-rock interaction in the sedimentary country rocks.  相似文献   

TG/plus—a pyrolysis method for following maturation of oil and gas generation zones using T_max of methane     

Jean Whelan  Robert Carangelo  Peter R. Solomon  Wallace G. Dow 《Organic Geochemistry》1990,16(4-6)

Thermogravimetric Fourier transform infrared spectroscopy (TG-FTIR) analyses were carried out on two sets of isolated kerogens covering a wide maturity range from low mature (0.46% R_o) through the end of oil and gas generation (maximum R_{o = 5.32%}). Data onweight percent and T_max for evolution of methane, volatile tars, ethylene, SO₂, NH₃, CO₂, and CO are reported. The T_max of methane shows the most consistent response to increasing maturation in both sets of samples. Results are comparable to those of whole rocks from an Alaskan North Slope well analyzed previously. The collective data for both whole rocks and isolated kerogens shows a generally linear correlation between %R_o and T_max of methane, with the exception of R_o of about 2.0% where a dip in the curve occurs. The slope of the correlation line was steeper for the predominantly terrigenous Wilcox kerogen than for more marine Colorado kerogen or for the Alaskan North Slope whole rock samples, probably reflecting differences in the chemical nature of various kerogen sets, which is also reflected by differences in the shapes of the pyrolysis curves of SO₂, CO₂, CO, H₂O, and ethylene. These preliminary data indicate that T_max of methane is a good maturation indicator for whole rocks and isolated kerogens up to an R_o of about 4%, which includes all of the wet gas and a considerable portion of the dry gas generation zones. This correlation was also observed for samples containing migrated bitumen, where it was not possible to obtain a reliable T_max for the volatile tar (S2) peak. The more terrigenous Wilcox kerogens also showed a good correlation of the T_max of ethylene with %R_o. T_max of ammonia evolution did not correlate with maturity and occurred 100–200°C lower than previously found for whole rocks, consistent with a whole-rock source of pyrolytic ammonia for Alaskan whole rock samples. HI and OI indices were calculated in several ways and plotted to reflect kerogen type as well as both the residual oil and gas generation potential. The ratio of pyrolyzable to combustible sulfur (evolved as SO₂) was independent of maturity and showed a clear difference between the more terrigenous Wilcox kerogens and the more marine Colorado kerogens.  相似文献   

Geology and Gold Mineralization in the Pan-African Rocks of the Adola Area, Southern Ethiopia     

Solomon Tadesse 《Gondwana Research》1999,2(3):439

Primary and placer gold deposits are mined from the Pan-African Adola volcano-sedimentary sequence, in southern Ethiopia. Two major mineralized belts can be recognized: the Megado (‘Gold Belt’) and the Kenticha Belts. The Kenticha Belt is also known for its rare metal mineralization. Extensive exploration of the area resulted in two most important primary gold deposits of Lega Dembi and Sakaro. The primary gold deposits are classified into four classes based on their geological setting:

- auriferous veins, lodes, stockworks and silicified zones disseminated in schistose rocks

- gold associated with quartzite

- gold mineralization confined to conglomerates and meta-arkoses

- auriferous quartz veins in high grade gneiss rocks

This classification provides a useful guide for future exploration programme  相似文献   

Phodong (Sikkim) earthquake of 14 February 2006 and its aftershocks—Coulomb stress analysis     

P. Solomon Raju  V.K. Gahalaut  M. Ravi Kumar 《Journal of Geodynamics》2008,46(1-2):63-67

The 14 February 2006 Phodong (Sikkim) earthquake of moderate magnitude (Mw 5.3) triggered several aftershocks that were recorded by a local seismic network. The thrust earthquake is part of the continuing earthquake activity in the Himalayan seismic belt region that occurs on the detachment or ramp under the Higher Himalaya. The aftershocks of the earthquake occurred in increased stress regions caused by the earthquake rupture. Triggering of aftershocks by such a moderate magnitude earthquake implies that the faults in the Himalaya are critically stressed and even a small change of stress, about 0.001–0.002 MPa, can trigger earthquakes on such faults.  相似文献   

Trapping Ionic Mercury Using Different Adsorbents     

Adedamola Titi Ojedokun  Abraham Olusegun Oluwole  Olugbenga Solomon Bello 《洁净——土壤、空气、水》2019,47(12)

Of recent, adsorption process has gained a lot of attention as a cheap and effective means of removing trace metals from wastewater prior to discharge into water bodies. Being flexible in design and operation, the process has enabled an optimal recovery of trace metals such that the treated effluents meet the desired standards for waste disposal. Mercury is a toxicant released into the environment from natural and anthropogenic sources. It is notorious for having an unusual tendency to bio‐accumulate and persist in the food chain. Presence of mercury in food, especially those of aquatic sources has drastic implications on human health. Therefore, efforts have been made to develop and optimize low‐cost activated carbon (AC) as adsorbents for scavenging mercury from aqueous effluents. Herein, how mercury accumulates across the food chain, its health implications, and the recent advancement in the use of low‐cost ACs as adsorbent for trapping mercury from wastewater are highlighted. Relationship between the mercury removal efficiency and the surface morphology of the adsorbents as well as the influence of prevailing experimental condition on the sorption process were addressed. Challenges and future prospects of the use of low‐cost adsorbents in addressing mercury pollution in the environment are discussed.  相似文献   

Testing a simulation model for reconstruction of prehistoric forest-stand dynamics     

Allen M. Solomon  Hazel R. Delcourt  Darrell C. West  T. J. Blasing 《Quaternary Research》1980,14(3):275-293

  相似文献   

Instantaneous global ozone balance including observed nitrogen dioxide     

Susan Solomon  Harold S. Johnston  Marta Kowalczyk  Ivan Wilson 《Pure and Applied Geophysics》1980,118(1):58-85

The catalytic destruction of stratospheric ozone by the oxides of nitrogen is believed to be an important part of the global ozone balance. The lack of sufficient measurements of NO _x concentrations has impeded efforts to quantify this process. Recent measurements of stratospheric nitrogen dioxide from ground-based stations as well as aircraft and balloons have provided a first approximation to a global distribution of NO₂ vertical columns at sunset. These observed vertical columns have been translated into time-dependent vertical NO₂ profiles by means of a one-dimensional atmospheric photochemical model. Using recent observations of air temperature and ozone along with this information, the independent instantaneous (one second) rates of ozone production from oxygen photolysis P(O₃), of ozone destruction from pure oxygen species (Chapman reactions) L(O _x ), and of ozone destruction by nitrogen oxides L(NO _x ) were estimated over the three-dimensional atmosphere. These quantities are displayed as zonal average contour maps, summed over various latitude zones, summed over various altitude bands, and integrated globally between 15 and 45 km. Although the global summation between 15 and 45 km by no means tells the complete story, these numbers are of some interest, and the relative values are: P(O₃), 100; L(O _x ), 15; L(NO _x ), 45±15. It is to be emphasized that this relative NO _x contribution to the integrated ozone balance is not a measure of the sensitivity of ozone to possible perturbations of stratospheric NO _x ; recent model results must be examined for current estimates of this sensitivity.  相似文献   

Formation,history and energetics of cores in the terrestrial planets   总被引：1，自引：0，他引：1  

Sean C. Solomon 《Physics of the Earth and Planetary Interiors》1979,19(2):168-182

The cores of the terrestrial planets Earth, Moon, Mercury, Venus and Mars differ substantially in size and in history. Though no planet other than the Earth has a conclusively demonstrated core, the probable cores in Mercury and Mars and Earth's core show a decrease in relative core size with solar distance. The Moon does not fit this sequence and Venus may not. Core formation must have been early (prior to ～4 · 10⁹ yr. ago) in the Earth, by virtue of the existence of ancient rock units and ancient paleomagnetism and from UPb partitioning arguments, and in Mercury, because the consequences of core infall would have included extensional tectonic features which are not observed even on Mercury's oldest terrain. If a small core exists in the Moon, still an open question, completion of core formation may be placed several hundred million years after the end of heavy bombardment on tectonic and thermal grounds. Core formation time on Mars is loosely constrained, but may have been substantially later than for the other terrestrial planets. The magnitude and extent of early heating to drive global differentiation appear to have decreased with distance from the sun for at least the smaller bodies Mercury, Moon and Mars.Energy sources to maintain a molten state and to fuel convection and magnetic dynamos in the cores of the terrestrial planets include principally gravitational energy, heat of fusion, and long-lived radioactivity. The gravitational energy of core infall is quantifiable and substantial for all bodies but the Moon, but was likely spent too early in the history of most planets to prove a significant residual heat source to drive a present dynamo. The energy from inner core freezing in the Earth and in Mercury is at best marginally able to match even the conductive heat loss along an outer core adiabat. Radioactive decay in the core offers an attractive but unproven energy source to maintain core convection.  相似文献