Center for research in economic geology creg, mackay school of mines169, university of nevada, reno, nevada 895570232 jon. Goldbearing breccias of the rain mine, carlin trend. The 144 zone is an oxidized, breccia hosted, disseminated gold deposit that formed along the contact between early cambrian carrara formation limestone and overlying bonanza king formation dolomite within the bare mountain range in southern nevada. Crackle breccia forms a capping over multistage hydrothermal breccias that are cut by tabular to pipeshaped tuffisite dikes, with some containing accretionary lapilli. The earlymiddle miocene san onofre breccia tso concurrent with or immediately after the formation of the topanga sandstone, great landslides fell down the slopes of a large landmass west of our present coastline. Thorkelson 1 codes arc centre of excellence in ore deposits, university of tasmania, hobart, tasmania, australia, 2 geological survey branch, primary industries and resources sa, south australia. Such a breccia, at the foot of reefs of mississippian limestones in great britian, has been described by tiddeman. Sample 72275 is a friable fragmental breccia from the edge of the serenitatis basin. The present study suggests that breccia is formed either by igneous. It is similar to a crackle breccia which is defined as a type of breccia where the clasts have been separated by planes of rupture but have experience little or no displacement shukla and sharma.
Miramont resources is a mineral exploration company with 2 properties in southern peru. The breccia pipe appears to plunge to the northnortheast at a steep angle and commonly grades outward into a marginal crackle breccia which ranges in width from a few metres to several tens of metres. Geologists working especially in the field of structural and ore geology get attracted towards. Overlying, and in places adjacent to the murray breccia, is a crackle breccia. These terms reflect, to some degree, the spatial relationship of fragments to one another primarily through their degree of mutual orientation. The average degree of rotational misfit of the clasts is strongly related to breccia class. In cracklebreccia, the clasts are a little rotated with respect to each other. Bulk unit weight kn m3 unit cohesion kn m2 friction angle. Mazama collapse caldera, with wizard island volcanic cone in the. A secondary breccia discriminant, more difficult to apply in the field, is the ratio of cement to matrix between the clasts. Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments over two millimeters in diameter. The rockflour type matrix has a variable participation, but it has obviously a minor participation less than 50%, sillitoe, 1985 as compared to the clasts. Geology and origin of mineralized breccia pipes in copper.
Evaluation of gas reservoirs in collapsed paleocave systems. Crackle and mosiac breccias are not to be expected. Glossary of fault rock terminology mcgill university. New approaches to exploration for iocgstyle mineralisation, middleback ranges, s. Fault breccias, or tectonic breccias, are a type of cataclastic rock formed by mechanical deformation during crustal movements glossary of geology, 2005.
Clastic particles in a sedimentary breccia are rounded and are about the same size as finegrained sand. Classification of fault breccias and related fault rocks. A mosaic breccia is one whose fragments have been largely but. Rubble breccia consisting of variably altered dolostone fragments and shale fragments in white dolomite cement. Gold mineralization occurs within a breccia body that contains a variety of breccia types. Catalina island is a remnant of that landmass and crystalline catalinatype rocks were eroded to form the san onofre breccia. To subdivide fault breccias, we advocate the use of textural terms borrowed from the cavecollapse literature crackle, mosaic and chaotic breccia with bounds at 75% and 60% clast content. Fv2 cs the high grade fv2 ms breccia grades into fine grained, heamatically kfeldspar altered clast supported cs brecciated felsic volcanics. Meteorite research at utct has involved gathering quantitative measurements from volumetric data, such as vesicle size distributions, impact breccia clast identification and measurement, and degree of metalmelt segregation. The matrix is composed of magnetite, carbonate, biotite with economic chalcopyrite and minor pyrite mineralisation.
The usu department of geosciences conducts interdisciplinary earth sciences research with a core of classical geology. Crackle breccia is a type of breccia where the clasts have been separated by planes of rupture, but have experienced little or no displacement. Mineralized breccia pipes are roughly cylindrical, near vertical structures ranging in diameter from 50 to 600 ft. The angular nature of the clasts indicates that they have not been transported very far from their source. Ore classification and breccia formation in the 144 zone. Thesis submitted in accordance with the requirements of the university of adelaide for an honours degree in geology. Hydrovolcanic breccia pipe structuresgeneral features and. The geological relationships of the breccia to the intrusive body offer the. Clast supported fv2 grades into low grade crackle breccia fv1. Dolomitization and brecciation increase from crackle breccia bodies along the wall rock to rubble breccia bodies near the center of the breccia. Pdf descriptive field classification of sedimentary and. Proterozoic iocg mineralised breccia system, yukon, canada 1 julie a. Mineralization and timing of the lovers lane breccia.
At one end, the rock is only crossed by a network of veins with minor displacement of fragments. Box 669, carlin, nevada 89822 abstract the rain mine includes two minedout open pits that contained 36. Mississippi valleytype deposits mvt lakehead university. A composite pile is composed of a central core of heterogeneous, rotated, angular to rounded rock fragments surrounded by a zone of nonrotated crackle breccia. An incipient breccia having fragments parted by planes of rupture but showing little or no displacement. The importance of individual breccia types and their geological implication has also. A crackle breccia, representing incipient brecciation, is one whose fragments are. It is further subdivided into flow breccia, which is. This breccia type is termed regolith breccia because it closely resembles consolidated lunar soil.
They are further classified as chaotic, mosaic, or crackle breccias based on. Like all wave and tide breccias, coral breccia is either a rubble or a pudding breccia. University of nevada, reno mineralization and timing of the lovers lane breccia, santa rita porphyry cumo deposit, grant county, new mexico a thesis submitted in partial fulfillment of the requirements for the degree of master of science in geology by randall l. Ellenburger group, permian basin, texas image logs facilitate differentiation of two potential primary reservoir types in the ellenburger group. Lunar breccias lunar petrographic thin section set study. It is further subdivided into flow breccia, which is formed by the. A breccia consisting of 3060% clasts over 2 mm in diameter.
A breccia consisting of 6075% clasts over 2 mm in diameter. Central kentucky mineral district university of kentucky. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Sample 15299 is a vitric matrix breccia that is probably from a small crater in the local lunar regolith at the apollo 15 site. The aggressive interaction of the breccia body with the host rocks during its. Early miocene volcanism associated with a maardiatreme breccia complex preceded mainstage epithermal gold mineralization at the kelian gold mine, kalimantan, indonesia.
In one example, more than 32,000 vesicles were analyzed in the ibitira vesicular basalt meteorite to. Morrow, 1982 pass transitionally to a breccia where clasts are. Geology of the area between eakin creek and windy mountain. Crackle breccias form as cracks either random or sheeted which. Geology of the mineralized kendall breccia bodies with.
An impact breccia is a breccia with clastic matrix or crystalline matrix derived from the crystallization of impact melt containing lithic and mineral clasts of different degree of shock metamorphism excavated by an impact from different regions of the target rock section, transported, mixed, and deposited inside or around an impact crater. Within the mineralized area only dikes andor sills related to the nelson intrusions were intersected in drilling. Click here to see list of references, authorities, sources and geographical terms as used in this glossary. Few geologic structures so lend themselves to diverse inter pretations as the beds of. Tectonic breccias are major importance for mineralisation in metamorphic terraines. Goldbearing breccias of the rain mine, carlin trend, nevada. Hydrothermal breccia pipe structures general features and genetic criteria 59 matrix the rock fragments are also accompanied by matrix andor hydrothermal cement. Classification of fault breccias and related fault rocks core. Ore type characterisation at the ernest henry cuau mine.
Breccia breccia is a rock formed from angular gravel and bouldersized clasts cemented together in a matrix. The individual clasts in crackle breccia must not have experienced more than 10 average rotation. Petrogenesis of crackle breccia at puente posada the crackle breccia at puente posada see figure below shows a relict intraclast. The lukkacha project is a copper exploration property targeting porphyry style mineralization within a wellknown copper district of peru. The matrix is confined to the seams and is commonly a chemical deposit. Mosaic breccia with sphalerite crystals in white dolomite cement, robb lake, bc. Breccia is rock composed of sharpangled fragments embedded in a finegrained matrix. Because of the economic significance of these breccia bodies, it is important to understand the age and origin of. The cerro hermoso project is targeting breccia pipe mineralization with high grade copper and gold exploration targets. Rubble breccia consisting of variably altered dolostone fragments. The murray breccia, which is bedded and locally displays shrinkage cracks and slump folds, has recently been identified as a coarse pyroclastic deposit with associated thinner beds.
Diatreme breccias at the kelian gold mine, kalimantan. They are further classified as chaotic, mosaic, or crackle breccias based on percentage of large 2mm clasts woodcock and mort, 2008. A breccia consisting of at least 75% clasts over 2 mm in diameter. Comparison charts are provided for semiquantitative classification of fault breccias. Crackle breccia with disseminated sphalerite crystals in white dolomite cement, robb lake, bc. Volcanic breccia is a rock composed predominantly of angular volcanic fragments 2 mm in size set in a subordinate matrix of any composition and texture or composed of mineralrock fragments rather than volcanic set but in a volcanic matrix reynolds, 1928, anderson, 1933, macdonald, 1953, fisher, 1958, fisher, 1960. Some of these breccia bodies are several feet wide and contain clasts of dolomite fragments and black sphalerite cemented with a matrix of reddishbrown sphalerite.
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