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Автор(ы):Xiuli Wang
Издание:Gulf Publishing Company, Houston, 2009 г., 415 стр.
Язык(и)Английский
Advanced natural gas engineering

The role of natural gas in meeting the world energy demand has been increasing because of its abundance, versatility, and clean burning nature. As a result, new gas exploration, field development, and production activities are under way. This is especially true in places where natural gas was (until recently) labeled as “stranded.” Because a significant portion of natural gas reserves worldwide are located across bodies of water, gas transportation becomes an issue. We are dealing with many unique issues and facing many challenges in the entire “food chain” (upstream to midstream and downstream) of natural gas engineering.

Автор(ы):Cooke D.R., Holliday J.R.
Издание:Ore deposit and exploration technology, 2007 г., 19 стр.
Язык(и)Английский
Advances in Geological Models and Exploration Methods for Copper ± Gold Porphyry Deposits

This paper focuses on the relationships between the geological model and exploration techniques for porphyry Cu ± Au deposits, with reference to the discovery record and exploration practices over the past fifteen years. The porphyry model is built on a long record of study dating back to the 1960s which has been gradually refined to encompass differences and complexities in mineralization and hydrothermal alteration assemblages resulting from varying intrusion (‘porphyry’) chemistries, differing wallrock geochemical and structural controls, the upwards zonation into the lithocap environment, and the overprinting effects of deep weathering.

Издание:Sрringer, 2006 г., 262 стр., ISBN: 1402044690, 1402044704
Язык(и)Английский
Advances in the Geological Storage of Carbon Dioxide

This volume organise presentations given by leading international researchers at a NATO Advanced Research Workshop on the state-of-the-art of geological storage of CO
2. The book is divided into 5 parts. Part 1 provides background by describing how human activities are modifying the atmosphere in industrially-active areas in Siberia. Part 2 outlines the innovative idea of using deep permafrost layers as either impermeable boundaries below which CO2 can be injected or as a cooling source for the formation CO2 clathrates. Part 3 describes recent studies conducted on naturally occurring CO2 reservoirs, sites which have the potential to help us understand the possible long-term evolution of CO2 storage sites. Part 4 outlines various industrial-scale applications of CO2 geological storage and shows it to be technically practical, economically feasible and, to date, very safe. Finally Part 5 gives us a view of the future, showing how energy uses are predicted to change over the next 50 years and how the public must be involved in any future decisions regarding climate change abatement.

Источник:twirpx
Издание:СО РАН НИЦ ОИГГМ, Новосибирск, 1993 г., 94 стр., ISBN: 5-7323-1784-6
Язык(и)Английский
Age and chemical composition of the Zhamanshin crater impactites and tektites and comparison with Australasian tektites

ТЬе Zhamanshin impact ci'ater is the only impact crater оп the Earth where impactites, various tektites and microtektites coexist. Тhus the Crater becomes the best object to solve the old tektite puzzle. Published before and new data оп the radiogenic ages and chemistry of the Zhamanshin tektites and Australasian tektites summarized to demonstrate their close genetic relations. ТЬе tektite age-paradox serves as the base evidence in favor of the exstraterrestrial origin of tektites. Тhe petrographical and petrochemical features of tektites demonstrate their most рсоЬаЫе volcanic origin.

Выпуск 94
Издание:Economic geology, 1998 г., 34 стр.
Язык(и)Английский
Age Constraints on Jerritt Canyon and Other Carlin-Type Gold Deposits in the Western United States— Relationship to Mid-Tertiary Extension and Magmatism

Carlin-type gold deposits are difficult to date and a wide range of ages has been reported for individual deposits. Therefore, several methods were employed to constrain the age of the gold deposits in the Jerritt Canyon district. Dated igneous rocks with well-documented crosscutting relationships to ore provided the most reliable constraints. K/Ar and 40Ar/39Ar dates on igneous rocks are as follows: andesite dikes 324 Ma, sericitic alteration in andesite dikes 118 Ma, basalt dikes 40.8 Ma, quartz monzonite dikes 39.2 Ma, and calc-alkaline ignimbrites 43.1 to 40.1 Ma. Of these, only the andesite and basalt dikes are clearly altered and mineralized. The gold deposits are, therefore, younger than the 40.8 Ma basalt dikes. The sericitic alteration in the andesite dikes is unrelated to the gold deposits. A number of dating techniques did not work. K/Ar and 40Ar/39Ar dates on mica from mineralized Ordovician to Devonian sedimentary rocks gave misleading results. The youngest date of 149 Ma from the smallest <0.1-)U,m-size fraction shows that the temperature (120°-260°C) and duration (?) of hydrothermal activity was insufficient to reset preexisting fine-grained micas in the host rocks. The temperature and duration was also insufficient to anneal fission tracks in zircon from Ordovician quartzites as they yield Middle Proterozoic dates in both mineralized and barren samples. Apatites were too small for fission track dating. Hydrothermal sulfides have pronounced crustal osmium isotope signatures (18'Os/188Osinitiai = 0.9-3.6) but did not yield a meaningful isochron due to very low Re and Os concentrations and large analytical uncertainties. Paleomagnetic dating techniques failed because the hydrothermal fluids sulfidized nearly all of the iron in the host rocks leaving no remnant magnetism.

Издание:PGS Publishing, Linden Park, 2002 г., 12 стр.
Язык(и)Английский
Alemao copper-gold (U-REE) deposits, Carajas, Brazil

The Alemao copper-gold deposit is located within the Carajas Mineral Province of Northern Brazil and was discovered in 1996 by DOCEGEO using geophysical and geological techniques. Alemao is hosted by the Igarape Bahia Group, which comprises two lithological and stratigraphic domains: a lower metavolcanic unit composed of metavolcanic rocks and acid to intermediate volcanoclastics; and an upper clastic-chemical metasedimentary unit with volcanoclastic rocks. The Alemao ore body is covered by a 250 metres thick unconfonnable siliciclastic unit referred as the Aguas Claras Formation. The ore body, which is 500 metres in length and 50 to 200 metres wide, strikes NE-SW and dips steeply to the NW, being emplaced along the contact between the two stratigraphic domains of the Igarape Bahia Group. In the ore zone, the hydrothermal paragenesis is marked by ferric minerals (magnetite-hematite), sulphides (chalcopyrite, pyrite), chlorite, carbonate (siderite, calcite, ankerite) and biotite, with minor quartz, tourmaline, fluorite, apatite, uraninite, gold and silver. Sericite and albite are rare. The mineralisation is represented by hydrothermal breccias and "hydrothermalites" classified into two types: (1) the BMS type, composed of massive bands of magnetite and chalcopyrite and by polymitic breccias with a matrix comprising magnetite, chalcopyrite, siderite, chlorite, biotite and amphiboles; (2) the BCLS type breccia which comprises brecciated hydrothermalised volcanic rocks with chalcopyrite, bornite, pyrite, chlorite, siderite, ankerite, tourmaline and molybdenite in the matrix, as well as dissemination in the rock. The geochemical association of Fe-Cu-Au-U-REE in iron rich, heterolithic, hydrothermal breccias at the Alemao Cu-Au Deposit, as well as its possible association with an extensional tectonic setting, suggests a correlation with Olympic Dam type mineralization. The total estimated ore resources based on a krigging method is 170 Mt @ 1.5% Cu and 0.8g/tAu.

Выпуск 98
Издание:Economic geology, 2003 г., 17 стр.
Язык(и)Английский
Alligator Ridge District, East-Central Nevada: Carlin-type gold mineralization at Shallow Depths

Carlin-type deposits in the Alligator Ridge mining district are present sporadically for 40 km along the north-striking Mooney Basin fault system but are restricted to a 250-m interval of Devonian to Mississippian strata. Their age is bracketed between silicified ca. 45 Ma sedimentary rocks and unaltered 36.5 to 34 Ma volcanic rocks. The silicification is linked to the deposits by its continuity with ore-grade silicification in Devonian-Mis-sissippian strata and by its similar δ18O values (~17‰) and trace element signature (As, Sb, Tl, Hg). Eocene reconstruction indicates that the deposits formed at depths of ≤300 to 800 m. In comparison to most Carlin-type gold deposits, they have lower Au/Ag, Au grades, and contained Au, more abundant jasperoid, and tex-tural evidence for deposition of an amorphous silica precursor in jasperoid. These differences most likely result from their shallow depth of formation.

Выпуск 63
Издание:Journal of Geochemical Exploration, 1998 г., 31 стр.
Язык(и)Английский
Alteration and primary geochemical dispersion associated with the Bulletin lode-gold deposit, Wiluna, Western Australia

The Bulletin lode-gold deposit is within the northernmost part of the Norseman-Wiluna greenstone belt in me Archaean Yilgarn Block, Western Australia. It is located within a brittle-ductile shear zone and hosted by tholeiitic metavolcanic rocks. Syn-metamorphic wallrock alteration envelops the gold mineralisation and is pervasive throughout the entire shear zone and extends up to 150 m into the undeformed wallrocks. Alteration is characterised by the sequence of distal chlorite-calcite, intermediate calcite-dolomite, outer proximal sericite and inner proximal dolomite-sericite zones. The thickness of the alteration envelope, and the occurrence of dolomite in the alteration sequence, can be used as a rough guide to the width, extent and grade of gold mineralisation, because a positive correlation exists between these variables. Mass transfer evaluations indicate that chemical changes related to the wallrock alteration are similar in all host rocks: in general, Ag, As, Au, Ba, C02, K, Rb, S, Sb, Те and W are enriched, Na and Y are depleted, and Al, Cr, Cu, Fe, Mg, Mn, Nb, Ni, P, Se, V, Zn and Zr are immobile, while Ca, Si and Sr show only minor or negligible relative changes. The degree of mobility of each component increases with proximity to gold mineralisation. The largest potential exploration targets are possibly defined by regional As (>6 ppm) and Sb (>0.6 ppm) anomalies. These anomalies, if real, extend laterally for > 150 m from the mineralised shear zone into areas of apparently unaltered rocks. Anomalies defined by Те (> 10 ppb), W (>0.6 ppm), carbonation indices, local enrichment of Sb (>2.0 ppm) and As (>28 ppm), and potassic alteration indices also form significant exploration targets extending beyond the HJB shear zone and the Au anomaly (>6 ppb) and, locally, into apparently unaltered rock. Gold, itself, has a restricted dispersion, with an anomaly extending for 1-35 m from ore, and being restricted to within the shear zone itself. Amongst individual geochemical parameters, only As and Sb define significant, consistent and smooth trends (vectors) when laterally approaching the ore. However, the respective dimensions of individual geochenucal anomalies can be used as an extensive, though stepwise, vector towards ore

Выпуск 96
Автор(ы):Jean S. Cline, Tracy L.C.
Издание:Economic geology, 2001 г., 18 стр.
Язык(и)Английский
Alteration associated with gold deposition at the getchell carlin-type gold deposit, North-Central Nevada

Wall-rock alteration at the Getchell underground deposit was examined to determine the effects of Au-bear-ing fluids on host lithologies and the relationship between K-bearing alteration minerals and Au deposition. The major, minor, and trace element geochemistry of highly altered and mineralized to unmineralized rocks from the Getchell deposit was quantified for more than 50 samples collected along 13 transects through calcareous siltstone and carbonaceous limestone and along one transect through a rhyodacite dike. Each transect in sedimentary rocks was collected along a single homogeneous bed that could be followed from high-grade ore to moderately altered rock or waste rock. Analyses were obtained for 39 elements, 10 oxides, and loss on ignition, using multiple techniques. Petrographic studies were integrated with geochemistry and X-ray diffraction and electron microbeam analyses to identify ore and alteration minerals and to correlate mineralogy with geochemical fluxes.

Автор(ы):David A.Johnson, Mark D.Barton
Издание:PGS Publishing, Linden Park, 2002 г., 18 стр.
Язык(и)Английский
Alternative brine source for Fe-oxide (-Cu-Au) systems: implications for hydrothermal alteration and metals

No single model satisfactorily accounts for the diverse characteristic of Fe-oxide-rich hydrothennal systems. Consideration of a spectrum of geologically reasonable models gives insight into the origins of variability among these deposits. Key features that need to be rationalized by any model are the abundance of hydrothermal magnetite and/or hematite, the chemically distinct suite of elements (REE-Cu-Co-Au-Ag-U), the variability of associated magmas, the distributions and volumes of associated hydrothennal alteration, and the broader geologic setting(s).

Geologic and geochemical evidence show that the ore-fonning fluids are brines, but the source of the brines is controversial. Multiple sources are possible, indeed likely. The identity and consequences of alternative sources - magmatic and non-magmatic are considered: First, by a review of plausible fluids and general consequences, second, by examination of the system characteristics, third, by specific consideration of the consequences of alternative models, and fourth, by consideration of selected systems where non-magmatic brines must play a major role.

We review some of the key characteristics of different types of hydrothermal Fe-oxide-rich(-Cu-Au) systems. Some are economic; many are only geochemically anomalous. Two end-members and several variants on these end members are proposed. One group is typified by relatively high-temperature mineralization, and relatively high K/Na and Si/Fe in the alteration. We suggest that these features (and others) are distinctive of magmatic fluid sources and that this group overlaps with porphyry Cu-Au and related deposit types. A second, broad group is typified by more oxide-rich, sulfide-poor mineralization, low Si/Fe ratios, and voluminous alkali-rich alteration where sodic types commonly exceed K-rich varieties. We suggest that the key features of this group reflect involvement of non-magmatic brines and that ore grades are less common as the metals are less easily trapped. Hybrid examples, where fluids of both types are involved, are expected (and known).

Conceptual and quantitative models of magmatic and non-magmatic fluid sources yield insight into the expected differences, the source and distribution of metals within these systems, and possible controls on ore deposition. These models highlight the difference between magma-sourced fluids and non-magmatic fluids. The former tend to be focused at the tops of magma chambers and have a built-in depositional mechanism -cooling. The latter require a different type of focusing mechanism - structural or stratigraphic, and different traps - mixing, specialized host rocks, and/or boiling. These models predict consistent differences in mineral assemblages, metal contents, alteration volumes, zoning, paragenesis, and geochemistry. For magmatic fluid sources, the models reproduce the key characteristics of that group, notably the porphyry-related systems. For non-magmatic brine sources, predicted characteristics match well with observations of Fe-oxide-rich systems in environments where these fluids are known to dominate, including mafic igneous systems and modem analogs such as the Salton Sea. These cases show that Fe-oxide (-Cu-Au-REE-Co) enrichments can result from non-magmatic sources. In other environments (e.g., with intermediate to felsic igneous rocks; settings deeper than ~5 km) the relative importance of various fluid sources and their consequences for mineralization remain to be fully explored. Young systems in the American Cordillera and elsewhere can help unravel the many threads that relate these enigmatic mineral deposits.

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