Поиск по книгам
Автор(ы):Parry W.T., Paula N.Wilson
Издание:Economic geology, 1996 г., 3 стр.
Characterization and dating of argillic alteration in the Mercur gold district, Utah—a reply

We would like to extend our appreciation to Morris and Tooker for their comments, discussion, and additional information that they provide pertaining to the geologic environment of the Mercur gold district, Utah. Their review of the characteristics of the Sevier orogenic belt are particularly relevant; however, such characteristics must be interpreted within the context of the additional geologic events of the region, which include the Jurassic compressional event that has been described from northern Utah and western Nevada. For this purpose, we offer the following reply.

Morris and Tooker have two main points of disagreement with our paper. First, they find the range of K-Ar ages we reported as disturbing and indicate that they date neither tectonic, hydrothermal, nor gold mineralization events; and second, they contend that all mineralized structures at Mercur must be younger than Late Cretaceous in age.

Издание:PGS Publishing, Linden Park, 2002 г., 20 стр.
Chilean Strata-bound Cu- (Ag) Deposits: An Overview

Strata-bound Cu- (Ag) deposits, long known as 'Chilean manto-type', occur along the Coastal Cordillera of northern Chile (22°-30°S) hosted by Jurassic and Lower Cretaceous volcanic and volcano-sedimentary rocks. These deposits are typical of the first stage of Andean evolution characterised by an extensional setting of the arc magmatism along the active margin of South America. Strata-bound Cu- (Ag) deposits were formed during two metallogenic epochs in the Late Jurassic and uppermost Early Cretaceous. The mineralisation took place at the time of structurally controlled emplacement of batholiths within the Mesozoic volcanic and sedimentary strata. The volcanic-hosted strata-bound Cu- (Ag) deposits invariably occur distal, but peripheral to coeval batholiths emplaced within tilted Mesozoic strata. The prevalent view that these deposits have an inherent genetic relationship with hydrothermal fluid derivation from subvolcanic stocks and dykes is contended here, because these minor intrusions are largely barren and this hypothesis does not fit well with Sr, Os and Pb isotopic data that call for crustal contribution of these elements. The strata-bound Cu- (Ag) mineralisation appears to be produced by fluids of mixed origin that were mobilised within penneable levels and structural weakness zones of the Mesozoic arc-related volcano-sedimentary sequence during the emplacement of shallow granodioritic batholiths under transtensional regimes. These hydrothermal fluids deposited copper and subordinate silver when reacted with organic matter, pyrite and/or cooled away from their heat sources. Although strata-bound Cu- (Ag) mineralisation took place during the same Cretaceous metallogenic event that formed the magnetite-apatite bodies, and Fe-oxide-Cu-Au deposits along the present Coastal Cordillera, the conceivable relationships with these other types of deposits are hampered by the inconclusive debate about the origin of the Chilean Fe-oxide deposits. However, the available data strongly suggest that the Fe oxide-rich deposits are metasomatic in origin and genetically related to contact zones of Lower Cretaceous dioritic batholiths, whereas the iron-poor volcanic-hosted Cu-(Ag) stratabound deposits constitute distal mineralisation peripheral to Upper Jurassic of Lower Cretaceous granodioritic batholiths.

Издание:PGS Publishing, Linden Park, 2005 г., 24 стр.
Chuquicamata, Core of a Planetary Scale Cu-Mo Anomaly

The copper and molybdenum mineralisation of the Chuquicamata deposit has been known since the 19' century. The deposit is located within the Codelco Norte District in the Andes Ranges of northern Chile, 200 km northeast of the city of Antofagasta. Small miners initially worked the exposed oxidised outcrops and high grade oxide veins that were the surface expression of the deposit, although industrial scale mining did not commence until 1915 with open pit exploitation of the main disseminated oxides. Mining has continued to the present day, currently removing approximately 170 000 tonnes of ore and 400 000 tonnes of waste per day.

Выпуск 91
Издание:Economic geology, 1996 г., 11 стр.
Clay alteration and gold deposition in the genesis and Blue Star Deposits, Eureka County, Nevada

The Genesis and Blue Star sedimentary rock-hosted gold deposits occur within the 40-mile-long Carlin trend and are located in Eureka County, Nevada. The deposits are hosted within the Devonian calcareous Popovich Formation, the siliciclastic Rodeo Creek unit and the siliciclastic Vinini Formation. The host rocks have undergone contact metamorphism, decalcification, silicification, argillization, and supergene oxidation.

Издание:The Geological Society, London, 2009 г., 373 стр.
Collision and collapse at the Africa–Arabia–Eurasia subduction zone (Коллизия и коллапс в Африкано-Аравийско-Евразийской зоне субдукции)

Настоящий сборник включает в себя 13 работ, в которых рассматриваются различные вопросы геодинамики, стратиграфии, истории геологического развития, магматизма, метаморфизма, кинематики региона, находящегося на стыке Африки, Саудовской Аравии и восточной Европы с позиций тектоники плит, т.е. как зоны субдукции и связанной с ней орогении.

The Society makes every effort to ensure that the scientific and production quality of its books matches that of its journals. Since 1997, all book proposals have been refereed by specialist reviewers as well as by the Society’s Books Editorial Committee. If the referees identify weaknesses in the proposal, these must be addressed before the proposal is accepted.

Once the book is accepted, the Society Book Editors ensure that the volume editors follow strict guidelines on refereeing and quality control. We insist that individual papers can only be accepted after satisfactory review by two independent referees. The questions on the review forms are similar to those for Journal of the Geological Society. The referees’ forms and comments must be available to the Society’s Book Editors on request.

Although many of the books result from meetings, the editors are expected to commission papers that were not presented at the meeting to ensure that the book provides a balanced coverage of the subject. Being accepted for presentation at the meeting does not guarantee inclusion in the book.

More information about submitting a proposal and producing a book for the Society can be found on its web site: www.geolsoc.org.uk.

Выпуск 83
Издание:Economic geology, 1988 г., 23 стр.
Comparative elemental and oxygen isotope geochemistry of jasperoid in the Northern Great Basin: evidence for distinctive fluid evolution in gold-producing hydrothermal systems

This comparative geochemical study of jasperoid in the northern Great Basin is based on 65 samples from 10 Carlin-type gold deposits and 22 similar but apparently barren hydro-thermal systems. Multielement geochemistry coupled with oxygen isotope data indicate that hydrothermal fluids in barren and mineralized systems evolved in different ways, and that there are fundamental geochemical differences among the various gold-producing deposits of the area.

Much of the variation in the jasperoid geochemical data can be explained in terms of seven abstract end-member components obtained through factor analysis. Three of these components (factors) dominate the results and are related to common products of alteration and mineralization in epithermal systems of the northern Great Basin. Element associations for these factors are: factor 1: Ti02, Al203, La, K20, Sr, Fe203, Th; factor 2: Au, Ag, Sb, Si02> As, Pb; and factor 3: W, B, V, Zn, Co, Au, CaO, Ni, Mn, Cu.

Выпуск 84
Издание:Economic geology, 1989 г., 3 стр.
Comparative elemental and oxygen isotope geochemistry of jasperoid in the northern great basin: evidence for distinctive fluide evolution in gold-producting hydrothermal system - a discussion

Discriminating productive jasperoids associated with economic gold mineralization from barren jasperoids, those with no known gold association, has long been an objective of Great Basin explorationists. Holland et al. (1988) use factor analysis of a multielement geochemical data set to compare jasperoids associated with Carlin-type gold mineralization with jasperoids in barren systems. They go on to propose a genetic model for Carlin-type deposits based on their interpretation of the factor analysis results. There are problems with their approach, several of which the authors acknowledge. The geologic control for their samples is inadequate, the analytical technique used is inaccurate for several critical elements, and their statistical analysis of the data could be much simpler, easier to interpret, and useful.

Издание:Economic geology, 1989 г., 6 стр.
Comparative elemental and oxygen isotope geochemistry of jasperoid in the Nothern Great Basin: evidence for distinctive fluid evolution in gold-producing hydrotermal systems - a reply

Brian K. Jones and Richard A. Leveille raise a number of points regarding the way in which our comparative study of jasperoid geochemistry (Holland et al., 1988) was framed and the implications that might be drawn from our results. Their primary concerns are with (a) the lack of geologic control for samples, (b) the accuracy of analyses for several critical elements, (c) the specific interpretation of factor 3 and its subsequent use in a discussion of genetic implications, and (d) the evaluation of analytical data by means of Q-mode factor analysis. We will address each of these concerns in turn.

Том 17, Выпуск 11
Издание:Elsevier, 1993 г., 11 стр.
Comparative rheological behaviour of albite and quartz in siliceous schists revealed by the microboudinage of piedmontite

This paper presents a detailed comparison of the microboudinage of piedmontite in two different mineralogical hosts, a quartz matrix, and albite porphyroblasts in a siliceous schist, with the aim of clarifying the rheological properties of albite in relation to those of quartz. Stress and strain analyses of the microboudinage confirm that the boudinage took place in the retrograde stage of metamorphism during decreasing temperature, and reveal that albite deformed at the same strain rate as quartz above the plastic-brittle transition temperature of albite.

Издание:PGS Publishing, Linden Park, 2002 г., 6 стр.
Comparison of the Geology of Proterozoic Iron Oxide Deposits in the Adirondack and Mid-Atlantic Belt of Pennsylvania, New Jersey and New York

Proterozoic hydrothermal iron oxide deposits occur within two metallogenic belts in the northeastern U.S.: the Adirondack region, and the Mid-Atlantic (Reading Prong) belt. A 175 km wide belt of Palaeozoic cover separates these two regions, although some iron deposits occur in Proterozoic rocks near the unconformity, suggesting a possible continuation beneath the cover. Although potentially part of the same continuous metallogenic province sharing similar mineralogy, host rock composition and hydrothermal alteration, deposits in the two regions differ in degree of deformation. Differences in the degree of metamorphic deformation fuel the debate of the relative timing of mineralisation, igneous activity, and metamorphism. Generally less deformed textures in the Adirondack deposits led workers in the New York deposits to conclude iron ores in the Adirondacks are associated with anorogenic granites that postdate peak metamorphism. Folded iron ores in granitic gneiss of the Mid-Atlantic belt suggest some deposits in eastern Pennsylvania, northern New Jersey, and southern New York predate peak metamorphism. REE-enriched deposits in both belts are characterised by abundant apatite, tourmaline, and manganese concentrations, as well as the presence of hematite-chlorite alteration in addition to magnetite. Unlike deposits hosted exclusively within granite gneisses, deposits within supracrustal rocks commonly contain significant sulphides and so are potential hosts for copper mineralisation.