Structural controls and origin of gold–silver mineralization in the Grampian Terrane of Scotland and Ireland

2014 ◽  
Vol 151 (6) ◽  
pp. 1072-1094 ◽  
Author(s):  
P. W. GEOFF TANNER
Keyword(s):  
Open Space ◽  
Hot Springs ◽  
Ground Surface ◽  
Maximum Principal Stress ◽  
Structural Controls ◽  
Quartz Veins ◽  
Dehydration Reactions ◽  
Gold Silver ◽  
Rhynie Chert ◽  
Fault Valve

AbstractGold-bearing mineral deposits occur over a strike distance of >300 km within the Grampian Terrane of Scotland and Ireland. This terrane consists of Neoproterozoic–Lower Ordovician rocks of the Dalradian Supergroup that were polyphase deformed and metamorphosed during the c. 470 Ma Grampian Orogeny. Sulphide-rich Au–Ag deposits occur in Scotland at Calliachar–Urlar Burn, Tombuie, Tyndrum and Cononish, and in Ireland at Curraghinalt (Omagh), Cavanacaw, Croagh Patrick, Cregganbaun and Bohaun. They are hosted by 0.1–6 m thick quartz veins and have a similar overall mineralogy, including native gold, As, Cu, Fe, Pb and Sn sulphides, with hessite, tetrahedrite and electrum present in the first six localities above. The mineralized quartz veins, which are characterized by open-space textures, crystallized at c. 3–5 km depth in the crust. All of the deposits were structurally controlled and, apart from Curraghinalt, occur within second-order Riedel R, R′ and T fractures resulting from a regional N–S-trending maximum principal stress. These deposits are of Upper Silurian to Lower Devonian (post-Scandian) age, and are inferred to have crystallized from hot, silica-rich metamorphic fluids derived from dehydration reactions at the greenschist/amphibolite-facies boundary. Curraghinalt is an older, Grampian, thrust-related deposit. Plutonic igneous rocks (mainly granitoid) contributed in part to the fluids, which were channelled into major orogen-parallel, strike-slip faults, to be injected by fault-valve pumping into the damage zones and fault breccias of newly formed Riedel fractures. Any residual fluid probably percolated to the ground surface to form Rhynie chert-type hot-springs.

The giant quartz-breccia veins of the Tyndrum–Dalmally area, Grampian Highlands, Scotland: their geometry, origin and relationship to the Cononish gold–silver deposit

2012 ◽  
Vol 103 (1) ◽  
pp. 51-76 ◽  
Author(s):  
P. W. Geoff Tanner
Keyword(s):  
Open Space ◽  
Fluid Pressure ◽  
Silver Deposit ◽  
Pore Fluid Pressure ◽  
Quartz Veins ◽  
Gold Silver ◽  
Coulomb Model ◽  
High Level ◽  
Transcurrent Faults ◽  
Cyclic Injection

ABSTRACTThe area lies within a ∼15 km-wide compartment of polyphase-deformed Dalradian (Neoproterozoic) rocks, bounded by the NE-trending Tyndrum and Ericht–Laidon transcurrent faults. Sinistral movement on these faults caused a periclinal structure, the Orchy Dome, to develop from flat-lying Dalradian rocks. This dome controlled the spatial distribution of lamprophyre intrusions and explosion breccia pipes, before being cross-cut by a network of near-vertical faults. Some of these faults are host to giant, segmented, quartz-breccia veins up to 5 km long and 19 m thick, formed by cyclic injection of over-pressured Si-rich fluid into newly-formed faults. The quartz-breccia bodies consist of a plexus of quartz veins with cockade and vuggy textures, indicative of open-space, high-level crystallisation. The faults comprise a NE-trending set of mineralised veins, including the Cononish Au–Ag deposit, and two pairs of conjugate [NW- and NE-trending] and [NNW- and NNE-trending], generally non-mineralised, faults. Their geometry is that predicted by the Coulomb model for Riedel R and R′ shear fractures, modified by variations in pore fluid pressure. They were active c. 430–425 Ma ago, coincident with emplacement of the Lochaber Batholith, whose buried extension, together with the mantle, probably provided the bulk of the fluid needed to form the veins.

Fluid regimes, fault-valve behavior and formation of gold-quartz veins — The Morro do Ouro Mine, Ribeira Belt, Brazil

2014 ◽  
Vol 56 ◽  
pp. 442-456 ◽  
Author(s):  
Angela Meira Faleiros ◽  
Ginaldo Ademar da Cruz Campanha ◽  
Frederico Meira Faleiros ◽  
Rosa Maria da Silveira Bello
Keyword(s):  
Quartz Veins ◽  
Fault Valve

Hydrology of a Southern Appalachian Hypocrene Spring-Fed Fen

2020 ◽  
Vol 26 (3) ◽  
pp. 359-366
Author(s):  
Jeffrey Wilcox ◽  
Emily Bradshaw Marino ◽  
Adam Warwick ◽  
Megan Sutton
Keyword(s):  
Open Space ◽  
Ground Surface ◽  
Early Spring ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Fractured Bedrock ◽  
Southern Appalachian ◽  
Discharge Rates ◽  
Hydrologic Restoration ◽  
Spring Flow

ABSTRACT Garland Seep is a Southern Appalachian fen that supports a population of federally endangered green pitcher plants (Sarracenia oreophila). The wetland is underlain by clayey stream deposits above fractured bedrock, is located at the base of a mountain slope, and is fed by groundwater that originates as recharge on the adjacent hillslope. Groundwater wells were installed following a hydrologic restoration in the mid-1990s and have been monitored at varying frequencies since that time. The 20+ year record provides evidence that Garland Seep can be classified as a “hypocrene fen,” in which spring flow rarely reaches the ground surface because of low discharge rates and high evapotranspiration (ET). In general, water-level fluctuations followed seasonal ET patterns, with higher water levels in the winter and early spring (when ET is low) and lower levels in the summer and fall. During wetter years, the water table remained near the ground surface for much of the year, with the clay layer underlying the site retaining moisture even after water levels had dropped. The “clay wetting” period was shorter during dryer years and corresponded with a reduction in the number of pitcher plant clumps observed at the site. In addition to the geologic and climatic controls on hydrology, previous landowners used fire to maintain open space for grazing, and The Nature Conservancy has continued the practice to combat woody vegetation and to open the canopy. Prescribed burns reduce ET (at least initially), cause a rise in water levels, and have helped maintain a thriving Sarracenia population.

Petrogenesis of amphibole – biotite – calcite – plagioclase alteration and laminated gold – silver quartz veins in four Archean shear zones of the Norseman district, Western Australia

1992 ◽  
Vol 29 (3) ◽  
pp. 388-417 ◽  
Author(s):  
Andreas G. Mueller
Keyword(s):  
Western Australia ◽  
Shear Zones ◽  
Wall Rock ◽  
Alteration Zone ◽  
Mining District ◽  
Low Grade ◽  
Fluid Temperature ◽  
Quartz Veins ◽  
The North ◽  
Gold Silver

The Norseman mining district in the Archean Yilgarn Block, Western Australia, has produced 140 t of gold and about 90 t of silver from 11.24 × 106 t of ore. The district is located within a metamorphic terrane of mafic and minor ultramafic greenstones, intruded by granite cupolas and swarms of porphyry dykes. The orebodies consist of laminated quartz veins, controlled by narrow (0.5–5 m) reverse shear zones that, in general, follow the contacts of metapyroxenite or porphyry dykes. Petrological studies of four shear zones, exposed on the Regent shaft 14 level, Ajax shaft 10 level, and in the stope above the North Royal shaft 5 level, show that the host rocks were metamorphosed to hornblende–plagioclase amphibolites and actinolite–chlorite rocks at temperatures of 500–550 °C prior to mineralization.At the localities studied, intense wall-rock replacement and low-grade (0.5 g/t) gold mineralization are confined to ductile or brittle–ductile shear structures. Alteration is similar in both ultramafic and mafic greenstones, and consists of an inner zone of biotite–quartz–calcite–plagioclase rock with minor actinolitic hornblende and quartz–calcite–actinolite veinlets, and an outer zone, locally developed, of chlorite–calcite–quartz rock. At an estimated pressure of 3 kbar (300 MPa), fluid temperatures during wall-rock alteration are constrained by the hydrothermal mineral assemblages to 480 ± 30 °C in two shear zones on the Regent shaft 14 level, and to 450 ± 20 °C in one shear zone in the North Royal shaft 5 level stope. The mole fraction of CO2 of the fluids is estimated at [Formula: see text], and the sulphur fugacity at 10−6 bar (10−1 kPa) (at 450 °C), based on the assemblage pyrrhotite + pyrite ± arsenopyrite. The development of an outer chloritic alteration zone at North Royal is related to the lower fluid temperature at this locality.High-grade (up to 75 g/t Au, 283 g/t Ag) veins formed within three of the shear zones studied at fluid temperatures of 400 °C and less, by the successive accretion of quartz laminae, separated by films of retrograde chlorite and sericite. The assemblage of ore minerals in the veins differs from that in the altered wall rocks, and includes disseminated galena, Pb–Bi–Ag tellurides, and native gold, which coprecipitated with the quartz. The orebodies at Norseman show affinities to Phanerozoic and Archean gold skarn deposits.

scholarly journals PANDUAN RANCANG RUANG TERBUKA DI JALAN JAMIN GINTING - PANCUR BATU

2018 ◽  
Vol 9 (1) ◽  
pp. 113-119
Author(s):  
Ulil Fahmi ◽  
Beny O.Y Marpaung
Keyword(s):  
Open Space ◽  
Ground Surface ◽  
Social Activities ◽  
Open Spaces ◽  
Functional Aspects ◽  
The Social ◽  
Sport Facility ◽  
Research Goal ◽  
Football Field

The football field located in the corridor of Jamin Ginting-Pancur Batu, District of Deli Serdang is one of open spaces in sub district of Pancur Batu, which both used as sport facility and place of feast celebration by the community. The football field has not been fully used since there are no facilities that can support the activities of the community. The football field is also often used in other activities, such as Pasar Malam that potentially damage the ground surface. The functional success of this open space can be achieved by redesign it by considering the proportion of aesthetics and functional aspects. The purpose of this research is to redesign the football field as an open space that can support the social activities of the community of Pancur Batu. This research will conduct by using descriptive-qualtative method. The research goal is to be a guideine that can be used to redesign the football field in Pancur Batu that fit the social activities of the community. By redesign the football field, it is expected to create an open space that can be an identity of the Jamin Ginting-Pancur Batu corridor.

Structural setting and timing of hydrothermal veins and breccias on Hurd Peninsula, South Shetland Islands: a possible volcanic-related epithermal system in deformed turbidites

1994 ◽  
Vol 131 (4) ◽  
pp. 465-483 ◽  
Author(s):  
Robert C. R. Willan
Keyword(s):  
Open Space ◽  
Hydrothermal Activity ◽  
South Shetland Islands ◽  
Shetland Islands ◽  
Quartz Veins ◽  
Intrusive Rocks ◽  
Extensional Faulting ◽  
High Level ◽  
The Antarctic ◽  
Main Vein

AbstractQuartz veins and vein-breccias in a greywacke-shale sequence of ?Carboniferous-Triassic age were previously regarded as mesothermal silicified fault breccias, and related to an adjacent Eocene granodiorite pluton. New mapping of vein assemblages and textures, and their structural and cross-cutting relationships, demonstrates that the steeply dipping, sheeted, epithermal-textured vein array was hydraulic in origin and possibly Cretaceous in age. The main vein and breccia swarm trends for 14 km NNE along-strike and 2 km across-strike, cutting large irregular areas of silicified and brecciated sandstone, and patchy areas of pyritic, propylitic and K-feldspar alteration. Angular vein fabrics and hydraulic disruption textures indicate wedging by hydrothermal solutions, hydraulic rupture, brecciation and fragment transport, followed by open-space precipitation, in veins generally < 15 cm thick and breccias up to a few metres thick. Hydrothermal quartz, chlorite, calcite and chalcedony predominate, with variable amounts of chalcopyrite, galena, sphalerite and pyrite. Epidote, arsenopyrite, K-feldspar and andradite garnet are conspicuous in places. Breccias were pre-and syn-mineralization, whereas mineral precipitation was pre-, syn- and post-breccia formation. Hydrothermal activity was simultaneous with extensional faulting, striking NNE, and accompanied by intrusion of dacitic dykes. There followed conjugate shearing on east- and ESE-striking faults, intrusion of high-level tonalite stocks, and several phases of basaltic andesite dyke intrusion. These hypabyssal rocks were probably coeval with the Antarctic Peninsula Volcanic Group dominating Livingston Island, dated between 130 and 75 Ma. Minor copper and iron sulphide-bearing veins occur in adjacent volcanic and hypabyssal intrusive rocks. The Hurd Peninsula veins may, therefore, form part of a volcanic-epithermal hydrothermal system (adularia-sericite-quartz type), of Cretaceous age, rather than a porphyry-related system of Eocene age.

scholarly journals Palaeoecology and palaeophytogeography of the Rhynie chert plants: further evidence from integrated analysis of in situ and dispersed spores

2017 ◽  
Vol 373 (1739) ◽  
pp. 20160491 ◽  
Author(s):  
Charles H. Wellman
Keyword(s):  
Hot Springs ◽  
Terrestrial Ecosystem ◽  
Land Plants ◽  
Integrated Analysis ◽  
Exceptional Preservation ◽  
Rhynie Chert ◽  
Floodplain Deposits ◽  
Early Land

The remarkably preserved Rhynie chert plants remain pivotal to our understanding of early land plants. The extraordinary anatomical detail they preserve is a consequence of exceptional preservation, by silicification, in the hot-springs environment they inhabited. However, this has prompted questions as to just how typical of early land plants the Rhynie chert plants really are. Some have suggested that they were highly adapted to the unusual hot-springs environment and are unrepresentative of ‘normal’ plants of the regional flora. New quantitative analysis of dispersed spore assemblages from the stratigraphical sequence of the Rhynie outlier, coupled with characterization of the in situ spores of the Rhynie chert plants, permits investigation of their palaeoecology and palaeophytogeography. It is shown that the Rhynie inland intermontane basin harboured a relatively diverse flora with only a small proportion of these plants actually inhabiting the hot-springs environment. However, the flora of the Rhynie basin differed from coeval lowland floodplain deposits on the same continent, as it was less diverse, lacked some important spore groups and contained some unique elements. At least some of the Rhynie plants (e.g. Horneophyton lignieri ) existed outside the hot-springs environment, inhabiting the wider basin, and were indeed palaeogeographically widespread. They probably existed in the hot-springs environment because they were preadapted to this unstable and harsh setting. This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.

Sign in / Sign up

Export Citation Format

Share Document