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By Daniel J. Corkery

Mines in Canada and the United States are subject to regulations limiting ammonia, nitrate and nitrite levels in mine effluents released into the environment. The primary source of these nitrogen compounds is typically explosive used in blasting operations, as ammonium nitrate (AN) remains a significant component of most explosives used in the mining industry. The amount of AN entering a local water drainage system is related to site conditions, explosives used, explosive handling and blast efficiency. Mining operators acknowledge AN loss to mine water from blasting operations. However, the mechanisms by which ammonia, nitrite and nitrate are entering the water drainage system, or the relative contribution of specific mechanisms, may not necessarily be assessed or monitored adequately. Characterization of these mechanisms, through systematic investigations, allows a mining operation to focus its efforts on reducing AN loss. This paper outlines a strategy for investigating the mechanisms through which AN enters the mine water drainage system and methods to mitigate this loss. This strategy includes collection and analysis of data to identify and quantify the AN loss mechanisms, design and implementation of tests to mitigate this loss, and assessment of the results. Such investigations are not intended to be a separate one-time project, but part of a long-term process of continual feedback and optimization that is related to the collection and reporting of AN levels for regulatory purposes. The implementation of the strategy must be tailored to each mine?s requirements and existing conditions.

Oct 1, 2010

By H. Gumede

The challenges of noise emission in the mining industry are well known. These challenges are exacerbated by the increasing trend towards mechanized mining, and there is general consensus that an effective industry-wide Buy Quiet initiative (BQI) will significantly assist in reducing noise-induced hearing loss by minimizing noise at its source. In its endeavours to improve the health of workers, the MOSH Noise Team has facilitated development of a proposed strategy and structure for a BQI. Extensive consultation with stakeholders resulted in support for the initiative. The MOSH Noise Team was advised to solicit the contributions of consulting mechanical and electrical engineers (CM&EEs), whose support is viewed as critical for realization of the initiative, since elimination of noise at source is an engineering challenge, and most procurement standards and specifications are set and managed by engineers. A workshop with CM&EEs and their representatives, as well as group environmental engineers (GEEs), confirmed the urgent need for the initiative and provided valuable insights. The workshop used obstacle based planning techniques to identify the factors on which the success of this BQI will depend. Most potential obstacles to the implementation revolved around proper scoping, leadership commitment, and companies? adherence to the initiative. Lack of involvement by the relevant stakeholders and economic issues were also identified as potential obstacles. Delegates at the workshop felt that the successful implementation of the industry-wide BQI, will depend on the mining industry addressing the specific obstacles. The most critical and urgent issue was identified as the formation of a properly constituted industry-wide BQI task team that includes representatives from critical stakeholder groups and which is mandated and empowered to drive the initiative.

Jan 1, 2014

By Rick W. Bellenie, Ronald L. Woolf

The Gregg River mine is located 40 kilometres (25 miles) south of Hinton, Alberta, approximately 330 kilometres (205 miles) west of Edmonton and lies against the Front Range of the Rocky Mountains.

Jan 1, 1994

By Norman O. Lotter

Drill core is preferred as the sample material for metallurgical and mineralogical characterisation and flowsheeting of an orebody. The question arises as to how to do this at the economic optimum, since geologists have several other strategic uses for their drill core. The limiting factors are the cost of extra drilling for the metallurgical testwork and the need to preserve the drill core record. In this study, the representative sampling of drill core at an economic optimum for metallurgical testing is addressed. This phase of the drill core work is preceded by earlier drill core characterisation - for which other appropriate sampling protocols are used - that has provisionally categorised the orebody into geometallurgical units. In stratified sampling of drill core, use is made of a version of the stratified approach to compound distributions proposed by Cochran in 1946. Use is made of Gy’s 50-piece minimum sample mass model to estimate minimum requisite sample mass. In the case where sampling and testwork are required on a Lifeof- Mine blend of a given ore deposit, whereby defined ore types or geometallurgical units are present, the sample mass requirement is significantly reduced by working from drill-core at the geometallurgical unit level. A case study using Raglan drill core is discussed. Using nickel as an indicator paymetal, and sampling at a fundamental variance level of 8%, the minimum sample masses for disseminated sulphides, net-textured sulphides, and massive sulphides are 3.80, 7.37 and 4.39 kg respectively. When the same drill-core is sampled as a Life-of-Mine mixture without knowledge of the geometallurgical units, the minimum sample mass increases to 84.28 kg. It is thus possible to assemble a representative Life-of-Mine sample of drill-core more economically, at the same time validating its representativity. Equivalent calculations for copper, platinum and palladium are discussed, with outcomes consistent with this finding. When all four paymetals are considered, one selects the largest minimum mass out of all four cases. This results in minimum sample masses of 11.67, 74.90 and 175.16 kg for disseminated sulphides, net-textured sulphides and massive sulphides respectively. The simulated Life-of- Mine blend would require a minimum sample mass of 377.33 kg to cover all four paymetals.

Jan 1, 2010

The authors describe two stratiform intrusions within a two miles thick ophiolite belt, one of the many ophiolite (serpentine) belts of the eugeosynclinal sequences of the Kalgoorlie System (metamorphic age c.2700 million years). Unusually good evidence of gravitational differentiation involving cumulates for an Alpine type peridotite-gabbro intrusion has been obtained, in spite of modifications of the original igneous rocks imposed by regional metamorphism. Unmetamorphosed relics of cumulate rocks are a surprising feature of this occurIfence.'fhe differentiation process reflected in the layered sequences is compared to that of the Stillwater Intrusion, Montana. Phase, cryptic and rhythmic layering are recognized. The economic significance of this study lies not only in the possibility of nickel mineralization in this ophiolite belt, but also in that much detailed information on the nature of these belts, which is difficult to obtain in the case of the more altered and sheared rocks of the belts carrying gold and nickel ore deposits nearby, is gathered from the Yilmia occurrences.

Jan 1, 1969

By Stanton RL

Stratiform lead-zinc mineralization in the Soldiers Cap Group and Kuridala Formation of the Mount Isa Inlier is closely associated with iron-rich sedimentary units or "iron formation", and has many similarities to the Broken Hill deposit in New South Wales. Both the Soldiers Cap Group and the Kuridala Formation have been intensively explored for deposits of this type since the early nineteen- seventies. A mineralized belt of at least eight significant prospects has been identified, of which the Pegmont deposit is the largest and best known example. In most cases the mineralized horizons contain banded galena and sphalerite within a gangue of predominantly quartz-garnet- pyroxene-amphibole rock, sometimes containing a variety of other metamorphic silicates, and apatite. Chemically, the mineralized horizons are distinguished by higher than usual levels of one or more of total Fe, MnO, CaO and P205. Interpretation of patterns of mineral- ization within the belt is based on the Pegmont deposit, where a model of base metal sulphide deposition within restricted basins of iron-rich chemical sediment has been developed (Stanton and Vaughan, 1979). Broadly, the model envisages the deposition of higher grade lead-rich mineralization in the basin centre position, lower grade zinc- rich mineralization in a basin intermediate position, and much weaker copper-rich mineralization in a basin edge position. These three positions reflect a laterally continuous arrangement of silicate microfacies within the original iron-rich sediment.

Jan 1, 1984

The overall mineral assemblage of the Broken Hill orebody is similar to that of a skarn. However unlike the classical skarns it does not represent contact metamorphism of pre-existing limestone beds. It is a stratiform accumulation of exhalative-sedimentary silica, sulphides, (Ca, Fe, Mn) silicates and carbonates, fluoride and phosphate that has later undergone regional metamorphism. The resulting development of coarse-grained quartz, sphalerite, galena, rhodonite, bustamite, mixed carbonates, fluorite, apatite and many minor phases has produced a sulphide-rich skarn- like mass that like many others of its kind, might best be referred to as a stratiform skarn. Recent investigations of occurrences of this type are showing that the incidence of concentrations of particular metamorphic minerals in and adjacent to such orebodies are closely related to bedding and to former sedimentary facies patterns. From this it appears that the mineral assemblages may be used to deduce not only the nature of the materials laid down in the beds, but also the physico-chemical conditions under which sedimentation took place. Several stratiform deposits, including Broken Hill, are used as examples to show that variations in these conditions may have a profound influence on the subsequent response of the rock to regional metamorphism and hence on the mineral assemblages that finally develop.

Jan 1, 1983

GENERAL GEOLOGICAL DESCRIPTION The uranium mineral appraisal herein described was made for an ore deposit in New Mexico. The uranium mineralization occurs as roughly tabular to lens-shaped deposits of varying thickness within the sandstone of the Jackpile formation of Jurassic age. The mineralization occurs at several horizons within the Jackpile formation, but is not always confined to specific beds. It often transgresses across stratigraphic layers, as demonstrated when attempting correlation of uranium gamma anomalies between adjacent drill holes. Preferred mineral trends have been established in some parts of the deposit, but are not always predictable when attempting to extrapolate beyond the zones defined by drill hole sampling. MANAGEMENT OF DRILL HOLE SAMPLE DATA All of the drill hole sample data used in the appraisal were obtained from interpretation of gamma-ray logs. A brief description of gamma-ray log sampling is given in Chapter 2. Two preliminary steps are involved in preparing gamma-ray logs into sample data normally acceptable for computer manipulation. 1) The gamma analog trace produced by the downhole probe must be digitized, i.e., counts-per-second (CPS) are recorded for each 0.15 m (1/2-ft) interval across the gamma-ray anomaly. The work is usually done on a "digitizer" while following the analog trace with an electronic stylus on a special tablet or table. The other alternative is to do the work manually. Some of the newest downhole logging equipment produces a magnetic tape output which can be read by a computer. 2) The gamma-ray CPS values must then be converted to equivalent U308 assay values, taking into consideration all appropriate correction factors. The US Atomic Energy Commission, now part of the Department of Energy, developed the theory and algorithm for this conversion in the 1960's, and though the work can be done manually, it is best done with the GAMRED (gamma-reduction) computer program. Fig. 14-1 illustrates a typical analog trace produced by the probe instrumentation, including gamma-ray trace (left), self-potential electric log (center), and resistivity log (right). Fig. 14-2 shows a form of the computer output after the analog data has been digitized to 0.15-m (1h-ft) intervals and converted to percentage U308 values for the same hole. The U308 grade bar graph on the right permits rapid visual inspection of anomalous values by depth and elevation. The converted U308 sample data were next processed by the SURVEY program that assigned to each assay interval [0. 15-m (1h-ft)] an X Y Z coordinate, taking into account all deviations indicated from downhole survey information. The output file of the SURVEY program was listed on the line printer for examination by project geologists, and also became the main input file for the URAN/ COMP compositing program, which is designed to group individual 0.15-m (/-ft) U308 sample values into larger intervals representing discrete anomalous zones according to a series of specified parameters entered into the program by the user. Composite U308 intervals were computed by the URAN/COMP computer program, the logic of which may be briefly described as follows: Step 1 The program searches for the highest U308 value in the hole and builds a composite by adding the highest grade interval on either side so long as the added value is greater than a minimum acceptable grade, and the total composite, after addition, meets minimum GT (grade times thickness) constraints. Step 2 The program loops back to find the next highest assay value in the hole not already included into a composite, until all anomalies above minimum cutoff grade are composited. Step 3 Individual composites are combined if they are closer than a specified minimum waste thickness, and the resultant composite grade still meets GT minimums.

Jan 1, 1980

By A. Hynes, T. Skulski, D. Francis

The Archean volcano-sedimentary succession in the LG-3 area has undergone two phases of deformation and has been metamorphosed to upper greenschist and amphibolite facies. Marine, fine-grained sediments and mafic pyroclastics comprise the lowest observed stratigraphic unit. These sediments are overlain by a thick sequence of submarine basalts and minor basaltic andesite. The lavas are characterized by high Al/Al+Si, Ti values, low Mg numbers and flat REE profiles (lOx chondrite). A sedimentary prism of coarse elastics which was deposited close to an exposed plutonic highland, overlie the volcanics. Massive lavas of basaltic andesi te and associated volcano-sediments comprise the uppermost stratigraphic unit. These lavas are characterized by high Mg numbers, Ni, Cr, LREE (lOOx chondrite) but low Ti, Al/Al+Si and HRee. The supracrustal rocks were intruded by tonalites and tonalitic gneisses.

Jan 1, 1984

The Myally Beds, Surprise Creek Beds and Mount Isa Group form the upper part of the Proterozoic Western succession of rocks in northwest Queensland. The latter two units are partly equivalent, and are important for their base metal content at Mount Isa and elsewhere. The arenaceous Myally Beds lie unconform- ably or disconformably below the Mount Isa Group and Surprise Creek Beds; they contain four mappable units which were deposited on a broad, shallow shelf washed by east-trending currents. Emergence of the Myally shelf initiated a series of parallel, possibly intra- cratonic, troughs to the east and west. In the east, the Surprise Creek Beds were deposited between the emergent shelf and base- ment rocks, and consist of a shelf and trough facies divisible into 7 and 10 units, respectively. Trough sediments are continuous north-south, and show turbidite character- istics; algal dolomite characterizes the shelf facies. To the west in the Mount Isa trough, an orthoquartzite facies, the Warrina Park Quartzite, defines the base of the Mount Isa Group. Hinge zones between the shelf and trough environments are marked by east-west facies changes, and provide a focus for later major north-south faulting. However, some penecon- temporaneous faulting near Mount Isa is best explained as complex post-depositional faulting of a disconformable sequence. Subsidence and deposition in the Mount Isa trough continued for a longer period than in the Surprise Creek trough, allowing accumulation of lead and zinc deposits in the upper half of the sequence. The Surprise Creek Beds appear equivalent to the lower half of the Mount Isa Group, and are probably not prospective for lead and zinc. Turquoise and possible other secondary copper minerals are widespread in the Warrina Park Quartzite and equivalents in the Surprise Creek Beds, and further investigation of these formations seems warranted.

Jan 1, 1974

By I. Dimitrov, S. R. McCutcheon

"Industrial-grade limestone is found in both the Lower Silurian La Vieille Formation and Upper Silurian LaPlante Formation of the Chaleurs Group in northern New Brunswick. Currently, between 150 000 and 200 000 tonnes of limestone are produced per year from the proximal facies of the LaPlante Formation at the Sormany quarry of Elmtree Resources Ltd., located west of Bathurst.The proximal facies of the LaPlante Formation was deposited on the margins of tectonically uplifted Ordovician terranes. This facies comprises stromatoporoidal-algal bindstone intercalated with wackestone, packstone, and floatstone in variable proportions. The distal facies comprises calcareous shale and minor limestone deposited deeper offshore.Folding and faulting related to Middle Devonian Acadian tectonism have caused an increase in the apparent thickness of the limestone sequences, especially adjacent to the regional Rocky Brook-Millstream fault. Structural and stratigraphic observations indicate that some of the limestone bodies in the area have been tectonically displaced from their site of deposition.A variety of prospecting techniques was used to locate new limestone resources, including geological mapping, airborne and ground electromagnetic surveys, and satellite remote sensing. Clastic rock units above and below the LaPlante Formation have distinctive properties that help to trace the intervening limestone along strike. Because of water-saturated glacial cover, thick vegetation, and the small size of targets, airborne geophysical methods did not prove effective in delineating limestone beds, but aeromagnetic surveys helped map the underlying clastic unit. The remote-sensing data and especially high-resolution digital elevation models helped in identification of karst topography related to limestone."

Jan 1, 2007

By W. A. Padgham, H. Helmstaedt

Field evidence for current hypothe e about age and kinematic ignificance of gold-bearing hear zones in the Archean Yellowkni fe greenstone belt is reviewed , and it is concluded that major disagreements between previous workers are a direct result of differences in stratigraphic and tructural in terpretations of the Yellowknife Supergroup. Although goldbearing hear zone appear to be confined to the mafic volcanic pile of the Kam Group. it can be shown that shearing affected all supracru tal rocks, including the Jackson Lake Formation. now con idered to represent the youngest unit of the Yellowknife Supergroup. tructural ob ervations are incompatible with the hypothe is that the hear zones represent loci of ynvolcanic gravity sliding but are consistent with earlier conclu ions that shear zone development commenced with rotation of the volcanic pile and continued as re ult of lateral shortening broadly overlapping with the emplacement of granitoid batholiths. Shear Zones are common throughout the entire green tone belt. yet productive zone are confined to the Yellowknife Bay Formation of the Kam Group and localized where flow abut with a high angle again t the contact of the We tern Plutonic complex. However. no obvious tructural and lithological features have been recognized that are more favorable for gold deposition and distinguish the shear zones and flows of the area around the mines from those of other parts of the greenstone belt. The model that gold wa transported by metamorphic solutions and that hear zones were the firs t-order control for gold deposition provides no explanation for the trong localization of the depo it . As porphyries with elevated gold contents are present in and near ome of the mines. the possibility that gold was deposited from hydrothermal system around fel ic intrusion representing early phases of the Western Plutonic complex should be given erious consideration.

Jan 1, 1986

E Deposit is located at BHP BillitonÆs Area C iron ore operations in the central region of the Hamersley Province, Western Australia. It is hosted by the Marra Mamba Iron Formation, the lowermost unit of the Archaean to Lower Proterozoic Hamersley Group. Mineralisation at E Deposit East is contained within the Mount Newman Member of the Marra Mamba Iron Formation and extends into the lower West Angela Member of the overlying Wittenoom Formation. Use of a combination of geological and geophysical techniques has enabled the geological setting of the deposit to be qualified. Interpretation of detailed mine face mapping, downhole geophysics, geochemistry, geological logging and photography has identified D2- related thrust faulting, with substantial south-over-north displacement. Similarly, in-pit mapping at the nearby C Deposit has revealed intense localised D2 deformation, including overturning and thrust faulting. The interpreted structure illustrates that iron ore deposits in the central Hamersley Province can be intensely deformed and require detailed geological investigation utilising technical data from mapping and drilling to enable the creation of robust grade-models for the mining operation.

Jan 1, 2007

By Trygve Høy

"Important stratabound lead-zinc deposits in southeastern B. C. occur in rocks that range in age from Proterozoic Helikian to Middle Cambrian. The Sullivan deposit, and similar but smaller deposits in the Sullivan area are the only important deposits that occur in clastic rocks with little carbonate content. The highly deformed and metamorphosed Shuswap deposits, of probable Hadrynian to Helikian age, are in mixed marble, calc-silicate gneiss and pelitic schist assemblages, rocks transitional between clastics and carbonates. Deposits in younger rocks, such as the Kootenay Arc deposits in the Lower Cambrian Badshot-Reeves Formation and the Monarch -Kicking Horse deposits in Middle Cambrian dolomite, are hosted by platformal carbonate rocks.An important regional control for the distribution of deposits appears to be a northeast-trending tectonic zone that crosses the Rocky Mountains and the Purcell Mountains just south of the Sullivan area, and projects southwestward toward the Salmo camp at the southern end of the Kootenay Arc. Pronounced northeast-trending gravity and magnetic anomalies, basic volcanism of Hadrynian age (the Irene volcanics west of Creston) and a preferred alignment of Mesozoic granitic rocks indicates that the zone coincides with deep crustal structures. Within the zone are dramatic and abrupt thickness and facies changes in Hadrynian Windermere rocks and lower Paleozoic rocks, and on the east side of the Rocky Mountain Trench in Helikian Purcell Supergroup rocks, indicating that block-faulting was active intermittently within the zone from Helikian through to lower Paleozoic time. Right-lateral and reverse movements occurred on northeast-trending tear faults within the zone in Mesozoic time."

Jan 1, 1982

By Otis M. Clarke

Observations of the land surface show that subsidence over active and abandoned underground mines is controlled to some extent by the stratigraphic and structural geology of the mines in addition to the methods of mining and the thickness of the seam mined. Exposures in highwalls of surface mines that intersect abandoned underground mines in the Warrior coal basin of Alabama illustrate this, showing sandstone beds that act as beams bridging openings and interbedded shale beds crumbling. Stratigraphic changes observed in the district are extremely variable and calculations regarding subsidence used for one area will not apply to another area if there is a major change in rock types Rocks exposed in road cuts and open pit mines demonstrate a marked difference in weathering characteristics. Some rocks, such as shale, wea- ther very rapidly, by crumbling and becoming plastic, whereas other rocks, such as sandstone, resist weathering. The continuing rock weathering after mining in openings produced by the mining activity and in fractures caused by roof movement, apparently, is a major cause of the surface sub- sidence that may occur years after the mines are abandoned.

Jan 1, 1986

By Gregg W. Morrison

"The Craigmont copper-iron skarn deposit is adjacent to the southern margin of the late Triassic Guichon Creek batholith in south-central British Columbia. Host to the ore are sedimentary and volcanic rocks of the western calc-alkaline belt of the Upper TriassicNicola Group. In the mine area, the Nicola Group rocks are a stratigraphically complex sequence, at least 1800 feet thick, which have been subdivided into Basalt, Rhyolite, Carbonate and Clastic Sediment units. All the units strike and dip parallel to the margin of the Guichon Creek batholith and are within the batholith contact aureole. However, only the Clastic Sediment unit is in contact with the batholith.Most of the skarn and ore is within the Carbonate unit and more specifically within an Interbedded facies that consists of lime sandstone, lime siltstone, quartzo-feldspathic siltstone and argillite. The Interbedded facies and the adjacent barren Massive Limestonefacies are interpreted aspart ofa carbonate reef complex. The distribution of skarn and ore within the Interbedded facies suggests that the facies boundary was a physical and chemical barrier that resulted in concentration of metals adjacent to the Massive Limestone facies.Two stages of skarn formation have been recognized at Craigmont. In Stage I, ore-bearing magnetite-rich and actinolite-epidote-magnetite skarns developed both in basaltic rocks and in Fe-bearing siltstone and argillite of the Interbedded facies, while barren grossular garnet-epidote-calcite-pyrite skarns developed in Fe-poor rhyolitic bands within the Interbedded and Massive Limestone facies . In Stage ll, massive, barren grandite garnet skarn replaced mineralized Stage I skarns in the vicinity of diorite plugs. and specularite ore formed in brecciated Stage I skarn and clastic rocks away from the plugs. Theformation of Stage I skarns required no addition of material, only redistribution and concentration of elements already present within the Interbedded facies. However, the concentration of Cu in Stage lore requires a mechanism for more efficient leaching of Cu from the host rocks, an anomalous concentration of Cu at the site of the Stage I orebody or an additional input of Cu from an external source. The formation of Stage II skarn and ore requires only remobilization and recrystallization of Stage I skarn and ore.Copper and iron are the only elements in economic concentrations in the ore and chalcopyrite is the only significant copper-bearing mineral. Chalcopyrite is disseminated and interstitial to magnetite in Stage I mineralized skarns and is interstitial to specularite in the matrix of Stage II breccia ores. Chalcopyrite also occurs with pyrite as stringer ore in bleached • sediments and rhyolite tuffs in the stratigraphic footwall of the main orebodies.The Craigmont deposit has more features in common with Cu-Fe deposits hosted in metavolcanic and metasedimentary rocks than it has with typical skarn deposits associated with porphyry copper deposits. The orebody is more likely a product of concentration of metal contained within the Nicola Group rocks than of the mineralizing event that produced the . Highland Valley Cu-Mo porphyry deposits in the central part of the Guichon Creek batholith ."

Jan 1, 1980

By J R. Kyle

The Deep Mill Level Zone (DMLZ) skarn Cu-Au deposit is the deepest explored part of the Ertsberg East Skarn System extending from the surface at 4200 m elevation to the DMLZ at 2900 to 2600 m. The DMLZ is hosted in an upper Cretaceous to lower Tertiary siliciclastic and carbonate succession adjacent to the 3 Ma Ertsberg pluton. Much of the DMLZ ore is hosted by mixed assemblages of siliciclastic and dolomitised carbonate strata that have been altered to Mg-rich skarn assemblages. Unaltered equivalent strata from a 300 m cored interval in the Yellow Valley Syncline were characterised petrographically and representative samples were analysed for major element compositions. These stratigraphic and chemical units are interpreted to be responsible for the varying skarn lithologies within the DMLZ. The dominant prograde skarn assemblages are controlled by protolith composition, notably the relative abundance of quartz, dolomite, and calcite within the protolith. Models based on isochemical metamorphism of mixed assemblages of quartz and dolomite suggest that the formation of the forsterite-diopside dominant skarn assemblages resulted in the greatest amount of pore space increase. DMLZ Cu-Au concentrations were locally controlled by host lithology, with structural features providing fluid pathways that focused the mineralising fluids. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Michel Gauthier

Several zinc showings, exhibiting many similarities to the well-known Balmat-Edwards zinc deposits of New York State, occur within the Grenville Supergroup strata of the Mont-Laurier Basin, Quebec. Metallogenic mapping programs have revealed much of the stratigraphic control of this mineralization. This control is observed on both regional and local scales. At the regional scale, these showings are confined to the perimeter of the Mt.-Laurier Basin, while at the local scale, a definite association between the zinc mineralization and dolomitic marble horizons is clearly exhibited from detailed mapping. These new exploration guidelines have proven to be useful for base-metal exploration in the Mt.-Laurier Basin and should be applicable to the entire Grenville Province.

Jan 1, 1983

By Odin D. Christensen

Gold deposits of the Carlin Trend occur within sedimentary rocks deposited across the Paleozoic continental margin. Lithologically dissimilar units, juxtaposed along the Roberts Mountains Thrust Fault system, constitute three distinct stratigraphic packages: autochthonous miogeoclinal carbonates, allochthonous eugeoclinal siliciclastic rocks, and an overlying coarse clastic overlap assemblage. Gold deposits occur within all three stratigraphic packages, with economic concentrations localized at structural and stratigraphic settings similar to those which host petroleum traps. Along structural breaks, gold is selectively concentrated within favorable stratigraphic units. Host stratigraphy controls the character of the ore, including average grade, grade variability, physical properties and metallurgical response.

Jan 1, 1989

By Hamilton TM

The Holocene Minninup shoreline is a coastal barrier system stretching from Bunbury to Busselton, in southwestern Australia. It has developed in a microtidal swell wave environment, under the influence of the post- glacial marine transgression and Holocene sea level variation. Barrier sediments thin rapidly across a shallow shelf, and consist of quartzo-felds- pathic sands with a minor skeletal carbonate component. Holocene shelf deposits are laterally extensive sheets overlying Pleisto- cene limestone. Modern carbonate production is small. Development of the Minninup barrier system has been controlled largely by low rates of sediment input from terrigenous and carbonate sources, late Holocene sea level fluctuati,.,s, and pre-existent coastal landforms composed of Pleistocene limestone. Modern controls on sedimentation are the refracted, shoaling swell wave regime, and onshore winds, which combine to promote nett northward longshore drift. Holocene barrier systems of the southern Swan Coastal Plain are of several different types. These include prograded sequences of beach ridges overlying shoreface sediments, such as is found at Rockingham and parts of Geographe Bay, and complex polygenetic systems typified by the Leschenault Peninsula. Pre- liminary investigations of the barrier stratigraphy of the Minninup shoreline indicate that both progradational and polygenetic sequences are present. The processes involved in shoreline development and heavy mineral accumulation are being studied using aerial photograph inter- pretation, beach profile monitoring, sampling, and granulometric analysis. This will lead to an enhanced understanding of the mechanisms of heavy mineral accumulation, and assist in the development of genetic models as aids for Exploration.

Jan 1, 1986