Geological setting of gold, western Wabigoon Subprovince, Canadian Shield: exploration targets in mixed volcanic successions

1988 ◽  
Vol 25 (12) ◽  
pp. 2075-2088 ◽  
Author(s):  
David R. Melling ◽  
Charles E. Blackburn ◽  
David H. Watkinson ◽  
Jack R. Parker
Keyword(s):  
Volcanic Rocks ◽  
Shear Zones ◽  
Canadian Shield ◽  
Field Mapping ◽  
Geological Setting ◽  
Intrusive Rocks ◽  
Volcaniclastic Rocks ◽  
Gold Bearing

The Archean volcanic rocks in the Cameron–Rowan lakes area may be divided into three distinct successions based on field mapping, petrographic studies, and lithogeochemical characteristics. The lowermost Rowan Lake Volcanics are tholeiitic pillowed basalts. These rocks are unconformably overlain by the Cameron Lake Volcanics, a mixed succession of tholeiitic massive and pillowed basalts and intermediate to felsic volcaniclastic rocks. The Brooks Lake Volcanics consist of tholeiitic basalts and represent the youngest volcanic rocks at the top of the preserved succession.Most of the gold concentrations in the Cameron–Rowan lakes area are confined to the mixed Cameron Lake Volcanics. The majority of these, including the Cameron Lake deposit, occur within shear zones near lithologic contacts. In the Eagle–Wabigoon and Manitou lakes areas there are similar stratigraphic subdivisions of the supracrustal rocks and many of the gold concentrations also occur in deformation zones within the mixed volcanic successions. The contrasting competencies among the basalts, the intermediate to felsic volcaniclastic rocks, and the intrusive rocks, which are characteristic of the mixed volcanic successions, localized stress during deformation, forming shear zones into which gold-bearing fluids gained access. The potential for successfully delineating economic gold concentrations appears greatest in the mixed volcanic successions within these areas and elsewhere in the western Wabigoon Subprovince of the Canadian Shield.

The Bail Hill Volcanic Group: alkaline within-plate volcanism during Ordovician sedimentation in the Southern Uplands, Scotland

1998 ◽  
Vol 89 (4) ◽  
pp. 233-247 ◽  
Author(s):  
E. R. Phillips ◽  
R. A. Smith ◽  
J. D. Floyd
Keyword(s):  
Small Area ◽  
Sedimentary Basin ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Volcanic Complex ◽  
Volcanic Group ◽  
Intrusive Rocks ◽  
Volcaniclastic Rocks ◽  
Formed Part ◽  
Basaltic Lavas

AbstractThe Bail Hill Volcanic Group (Caradoc) represents the largest, single volcanic complex exposed within the Ordovician turbidite succession of the Northern Belt in the Southern Uplands of Scotland. The group comprises a heterogeneous sequence of submarine lavas, volcaniclastic and intrusive rocks (up to 2 km thick), and crops out in a small area (c. 4 km2) around Bail Hill, north of Sanquhar. The Cat Cleuch Formation (older) is dominated by a sequence of autobrecciated basaltic lavas which contain large, zoned diopsidic clinopyroxene. The overlying Peat Rig Formation comprises a more mixed sequence of plagioclase-amphibole-phyric lavas, volcaniclastic rocks and contemporaneous volcaniclastic sedimentary rocks. The Cat Cleuch and lower part of the Peat Rig formations are cut by a vent breccia, the Bught Craig vent breccia, which formed part of the feeder to the upper part of the Peat Rig Formation. The Bail Hill volcanic rocks are alkaline in character, ranging from alkali basalt to trachyandesite in composition, possessing trace element characteristics and enrichment patterns typical of oceanic within-plate basalts. The Bail Hill Volcanic Group, although geochemically distinct, forms part of a mixed assemblage of tholeiitic and alkaline withinplate lavas within the Southern Uplands which are of broadly similar age, some of which are intercalated within the greywacke sandstone sequence. This assemblage clearly indicates that a period of extension and within-plate volcanism occurred during the early stages of the development of the Southern Uplands sedimentary basin.

A new look at the stratigraphy of the Yellowknife Supergroup at Yellowknife, N.W.T. — implications for the age of gold-bearing shear zones and Archean basin evolution

1986 ◽  
Vol 23 (4) ◽  
pp. 454-475 ◽  
Author(s):  
H. Helmstaedt ◽  
W. A. Padgham
Keyword(s):  
Volcanic Rocks ◽  
Shear Zones ◽  
Gold Deposits ◽  
Spreading Center ◽  
Group Status ◽  
Slave Province ◽  
Lake Formation ◽  
Group A ◽  
Sea Floor Spreading ◽  
Gold Bearing

Based on recent detailed mapping, a revised stratigraphic column is proposed for the rocks of the Archean Yellowknife Supergroup in the Yellowknife greenstone belt. The mafic volcanic rocks of the Kam Formation, previously thought to represent the oldest supracrustal rocks of the belt, overlap remnants of an earlier volcanic–sedimentary sequence, here referred to as the Octopus Formation. As its enormous thickness makes it too unwieldy to be described as a single formation, the Kam Formation is raised to group status and subdivided into four formations. It is proposed that the Kam Group should replace the Beaulieu Group in the Yellowknife area. The Chan Formation, at the base of the Kam Group, consists of multiple gabbroic intrusions that were emplaced into a carapace of pillowed flows. The intrusions locally resemble sheeted mafic dyke complexes in Phanerozoic ophiolites, thought to represent evidence for sea-floor spreading. The Crestaurum Formation, which overlies the Chan Formation, is characterized by massive and pillowed flows interlayered with a number of laterally continuous cherts and felsic tuffs. The Townsite Formation consists of rhyodacite breccias interbedded with felsic tuffs and pillowed dacites. The Yellowknife Bay Formation, at the top of the Kam Group and comprising massive and pillowed flows with pillow breccias and numerous interflow sediments, contains all the important gold deposits mined at Yellowknife. The Banting Formation, directly overlying the Kam Group and consisting of mafic to felsic volcanics, is also given group status and subdivided into two formations. Conglomerates and sandstones of the Jackson Lake Formation, formerly thought to separate the Kam and Banting groups, are considered to represent the youngest rocks of the Yellowknife Supergroup near Yellowknife. Gold-bearing shear zones clearly postdate deposition of the Banting Group, making the rocks of this group a potential target for gold exploration. The presence of remnants of a possible spreading center at the base of the Kam Group suggests that plate-tectonic processes were active during the formation of Archean supracrustal basins in the Slave Province.

Petrology and volcanology of the Mesoproterozoic igneous rocks of the Saint Francois Mountains terrane, southeast Missouri, USA

2021 ◽  
pp. 253-289
Author(s):  
Gary S. Michelfelder*
Keyword(s):  
Volcanic Rocks ◽  
Field Trip ◽  
Magmatic Activity ◽  
Field Guide ◽  
Intrusive Rocks ◽  
History Of ◽  
Granitic Intrusions ◽  
High Silica ◽  
Volcaniclastic Rocks ◽  
Magmatic History

ABSTRACT The Saint Francois Mountains are the physiographic expression of the central part of the Ozark Dome of southeastern Missouri. The mountains are made up of a quaquaversal-dipping series of Paleozoic units cored by the Mesoproterozoic-aged rocks of the broader Saint Francois Mountains terrane. The Saint Francois Mountains terrane lies within the Eastern Granite-Rhyolite province along the eastern margin of Laurentia and contains at least four mapped caldera complexes (Eminence, Lake Killarney, Butler Hill, and Taum Sauk), associated volcanic and volcaniclastic rocks, and four distinct types of intrusive units. The Mesoproterozoic rocks represent two major pulses of magmatic activity: (1) an older 1.48–1.45 Ga episode of caldera-forming volcanism and associated subvolcanic to massif-type granitic intrusions; and (2) a younger 1.33–1.28 Ga episode of bimodal intrusions. Volcanism included primarily high-silica rhyolite and volcaniclastic sediments associated with caldera-forming volcanism with lesser amounts of basalt and basaltic andesite that formed as flows and subvolcanic intrusions. The older (ca. 1.4 Ga) intrusive rocks can be divided into three broad categories: (1) granite massifs including the Butler Hill/Breadtray massif-type granites, (2) caldera ring–type granites such as the Silvermine Granite, and (4) mafic- to intermediate-composition intrusive rocks such as the Silver Mines Mafic Series. The younger (ca. 1.3 Ga) bimodal intrusions are represented by the highly evolved felsic Graniteville-types granites and the gabbros of the Skrainka Mafic Group. This field guide provides an overview of the magmatic history of the Mesoproterozoic rocks exposed in the eastern Saint Francois Mountains. Field-trip stops are divided into two days, highlighting well-known stops and lesser-known localities that illustrate the magmatic activity of one the premier igneous locations in the midcontinent region. The field trip is focused on two main areas. Day 1 focuses on the rhyolite sequence and associated caldera-forming eruption of the Taum Sauk caldera. Day 2 focuses on the volcanic rocks and granitic intrusions related to the Butler Hill caldera and ends with a visit to one of the youngest granitoids in the terrane, the Graniteville Granite. The field guide presents a summary of the volcanic history and petrogenesis of the Saint Francois Mountains rhyolites and granites.

An estimate of the oxygen isotope composition of a large segment of the Canadian Shield in northwestern Ontario

1977 ◽  
Vol 14 (5) ◽  
pp. 927-931 ◽  
Author(s):  
Yuch-Ning Shieh ◽  
Henry P. Schwarcz
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Weighted Average ◽  
Canadian Shield ◽  
Granitic Rocks ◽  
Large Segment ◽  
Metasedimentary Rocks ◽  
Northwestern Ontario ◽  
Intrusive Rocks ◽  
Composite Samples

The O18/O16 ratios of the plutonic and supracrustal rocks from a large segment of the Superior province of the Canadian Precambrian Shield in Ontario (total area 111 000 km2) have been determined, using 8 composite samples prepared from 8076 individual specimens. The δO18 values (in ‰) relative to SMOW are: granitic rocks, 7.6–8.6; basic intrusive rocks, 7.2; metasedimentary rocks, 9.2; and volcanic rocks, 7.6. The composites from the granitic, basic intrusive, and volcanic rocks display δ values very similar to their contemporary or younger equivalents reported in the literature. The metasedimentary composite shows significantly lower δO18 than most Phanerozoic and Proterozoic metasediments of comparable metamorphic grades, possibly reflecting the presence of a high percentage of little-altered igneous rock detritus in the Archean sediments. The weighted average δ value (according to percent outcrop of each rock type) of this part of the Canadian Shield is estimated to be 8.1‰.

scholarly journals From Ordovician nascent to early Permian mature arc in the southern Altaids: Insights from the Kalatage inlier in the Eastern Tianshan, NW China

Geosphere ◽  
2021 ◽  
Author(s):  
Qigui Mao ◽  
Jingbin Wang ◽  
Wenjiao Xiao ◽  
Brian F. Windley ◽  
Karel Schulmann ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Evolutionary Model ◽  
Early Permian ◽  
Calc Alkaline ◽  
Eastern Tianshan ◽  
Central Asian ◽  
Intrusive Rocks ◽  
Volcaniclastic Rocks ◽  
Felsic Volcanic ◽  
Potassium Enrichment

The Kalatage inlier in the Dananhu-Haerlik arc is one of the most important arcs in the Eastern Tianshan, southern Altaids (or Central Asian orogenic belt). Based on outcrop maps and core logs, we report 16 new U-Pb dates in order to reconstruct the stratigraphic framework of the Dananhu-Haerlik arc. The new U-Pb ages reveal that the volcanic and intrusive rocks formed in the interval from the Ordovician to early Permian (445–299 Ma), with the oldest diorite dike at 445 ± 3 Ma and the youngest rhyolite at 299 ± 2 Ma. These results constrain the ages of the oldest basaltic and volcaniclastic rocks of the Ordovician Huangchaopo Group, which were intruded by granite- granodiorite-diorite plutons in the Late Ordovician to middle Silurian (445–426 Ma). The second oldest components are intermediate volcanic and volcaniclastic rocks of the early Silurian Hongliuxia Formation (S1h), which lies unconformably on the Huangchaopo Group and is unconformably overlain by Early Devonian volcanic rocks (416 Ma). From the mid- to late Silurian (S2-3), all the rocks were exhumed, eroded, and overlain by polymictic pyroclastic deposits. Following subaerial to shallow subaqueous burial at 416–300 Ma by intermediate to felsic volcanic and volcaniclastics rocks, the succession was intruded by diorites, granodiorites, and granites (390–314 Ma). The arc volcanic and intrusive rocks are characterized by potassium enrichment, when they evolved from mafic to felsic and from tholeiitic via transitional and calc-alkaline to final high-K calc- alkaline compositions with relatively low initial Sr values, (87Sr/86Sr)i = 0.70391–0.70567, and positive εNd(t) values, +4.1 to +9.2. These new data suggest that the Dananhu-Haerlik arc is a long-lived arc that consequently requires a new evolutionary model. It began as a nascent (immature) intra-oceanic arc in the Ordovician to early Silurian, and it evolved into a mature island arc in the middle Silurian to early Permian. The results suggest that the construction of a juvenile-to-mature arc, in combination with its lateral attachment to an incoming arc or continent, was an important crustal growth mechanism in the southern Altaids.

Mafic igneous rocks and mineralisation in the Palaeoproterozoic Ketilidian orogen, South-East Greenland: project SUPRASYD 1996

1997 ◽  
pp. 66-74
Author(s):  
Henrik Stendal ◽  
Wulf Mueller ◽  
Nicolai Birkedal ◽  
Esben I. Hansen ◽  
Claus Østergaard
Keyword(s):  
Mineral Exploration ◽  
Volcanic Rocks ◽  
Shear Zones ◽  
Field Work ◽  
Igneous Rocks ◽  
Border Zone ◽  
The South ◽  
East Greenland ◽  
North West ◽  
Arc Setting

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Stendal, H., Mueller, W., Birkedal, N., Hansen, E. I., & Østergaard, C. (1997). Mafic igneous rocks and mineralisation in the Palaeoproterozoic Ketilidian orogen, South-East Greenland: project SUPRASYD 1996. Geology of Greenland Survey Bulletin, 176, 66-74. https://doi.org/10.34194/ggub.v176.5064 _______________ The multidisciplinary SUPRASYD project (1992–96) focused on a regional investigation of the Palaeoproterozoic Ketilidian orogenic belt which crosses the southern tip of Greenland. Apart from a broad range of geological and structural studies (Nielsen et al., 1993; Garde & Schønwandt, 1994, 1995; Garde et al., 1997), the project included a mineral resource evaluation of the supracrustal sequences associated with the Ketilidian orogen (e.g. Mosher, 1995). The Ketilidian orogen of southern Greenland can be divided from north-west to south-east into: (1) a border zone in which the crystalline rocks of the Archaean craton are unconformably overlain by Ketilidian supracrustal rocks; (2) a major polyphase pluton, referred to as the Julianehåb batholith; and (3) extensive areas of Ketilidian supracrustal rocks, divided into psammitic and pelitic rocks with subordinate interstratified mafic volcanic rocks (Fig. 1). The Julianehåb batholith is viewed as emplaced in a magmatic arc setting; the supracrustal sequences south of the batholith have been interpreted as either (1) deposited in an intra-arc and fore-arc basin (Chadwick & Garde, 1996), or (2) deposited in a back-arc or intra-arc setting (Stendal & Swager, 1995; Swager, 1995). Both possibilities are plausible and infer subduction-related processes. Regional compilations of geological, geochemical and geophysical data for southern Greenland have been presented by Thorning et al. (1994). Mosher (1995) has recently reviewed the mineral exploration potential of the region. The commercial company Nunaoil A/S has been engaged in gold prospecting in South Greenland since 1990 (e.g. Gowen et al., 1993). A principal goal of the SUPRASYD project was to test the mineral potential of the Ketilidian supracrustal sequences and define the gold potential in the shear zones in the Julianehåb batholith. Previous work has substantiated a gold potential in amphibolitic rocks in the south-west coastal areas (Gowen et al., 1993.), and in the amphibolitic rocks of the Kutseq area (Swager et al., 1995). Field work in 1996 was focused on prospective gold-bearing sites in mafic rocks in South-East Greenland. Three M.Sc. students mapped showings under the supervision of the H. S., while an area on the south side of Kangerluluk fjord was mapped by H. S. and W. M. (Fig. 4).

Age of the Grenville dyke swarm, Ontario–Quebec: implications for the timing of lapetan rifting

1995 ◽  
Vol 32 (3) ◽  
pp. 273-280 ◽  
Author(s):  
S. L. Kamo ◽  
T. E. Krogh ◽  
P. S. Kumarapeli
Keyword(s):  
Long Range ◽  
Volcanic Rocks ◽  
Canadian Shield ◽  
Dyke Swarm ◽  
Alkaline Complex ◽  
Southeastern Part ◽  
Time Marker ◽  
Continental Breakup ◽  
Iapetus Ocean

U–Pb baddeleyite and zircon ages for three diabase dykes from widely spaced localities within the Grenville dyke swarm indicate a single age of emplacement at [Formula: see text] Ma. The 700 km long Grenville dyke swarm, located in the southeastern part of the Canadian Shield, was emplaced syntectonically with the development of the Ottawa graben. This graben may represent a plume-generated lapetan failed arm that developed at the onset of the breakup of Laurentia. Other precisely dated lapetan rift-related units, such as the Callander Alkaline Complex and the Tibbit Hill Formation volcanic rocks, indicate a protracted 36 Ma period of rifting and magmatism prior to volcanism along this segment of the lapetan margin. The age of the Grenville dykes is the youngest in a progression of precisely dated mafic magmatic events from the 723 Ma Franklin dykes and sills to the 615 Ma Long Range dykes, along the northern and northeastern margins of Laurentia, respectively. Thus, the age for these dykes represents a key time marker for continental breakup that preceded the formation of the Iapetus ocean.

scholarly journals Mise En Évidence De Nouvelles Structures Géologiques Dans La Région De Brobo (Centre De La Côte d’Ivoire). Aide À La Compréhension De La Tectonique Du Paléoprotérozoïque Du Craton Ouest Africain

2018 ◽  
Vol 14 (18) ◽  
pp. 305
Author(s):  
Daï Bi Seydou Mathurin ◽  
Ouattara Gbele ◽  
Koffi Gnammytchet Barthélémy ◽  
Gnanzou Allou ◽  
Coulibaly Inza
Keyword(s):  
Cote D'ivoire ◽  
Field Data ◽  
Côte D’Ivoire ◽  
Volcanic Rocks ◽  
Shear Zones ◽  
Cote D’Ivoire ◽  
Metasedimentary Rocks ◽  
Large Structures ◽  
Côte D'ivoire ◽  
Ductile Shear Zones

The lithological and structural observations of the region of Brobo (Central Côte d'Ivoire) indicate a succession of metasedimentary rocks (micaschists with cordierite, silstones, graphitic sediments, sandstones with amphibole-garnet, etc.) intermixed with volcanic rocks (rhyolite, dacite, andesite, basalt and the volcanoclastics). The whole is intruded by granites with one or two micas, sometimes porphyries, granodiorites, gabbros, and granite gneisses. Interpretations of Landsat ETM+ , RadarSat-1 and SRTM remote sensing imageries, as well as field data, revealed several lineament directions which, after field control, correspond to major faults and shear zones. These large structures show the N-S, NE-SW, NNE-SSW, E-W, NWSE, and NNW-SSE orientations. The field data also made it possible to describe several structures and to propose a preliminary geodynamic model for the setting and structuring of the formations of this region. This model suggests that the geodynamic took place in three stages: distension with a deformation of basement formations generating a gneissocity (D1), as well as deposits of sediments in the basins; followed by a NW-SE to E-W convergence generating a cleavage in the volcanogenic series (D2). This phase of deformation continues while creating, locally, a strain slip cleavage or a transposed schistosity. The third cleavage affects the volcanogenic series (fractures cleavages, D3) and ends in large corridors of ductile shear zones and associated faults.

Gold-bismuth-telluride-sulphide assemblages at the Viceroy Mine, Harare-Bindura-Shamva greenstone belt, Zimbabwe

2008 ◽  
Vol 72 (4) ◽  
pp. 953-970 ◽  
Author(s):  
T. Oberthür ◽  
T. W. Weiser
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Close Association ◽  
Shear Zones ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Main Stage ◽  
Melting Temperatures ◽  
Native Bismuth ◽  
Gold Bearing

AbstractGold mineralization at the Viceroy Mine is hosted in extensional veins in steep shear zones that transect metabasalts of the Archaean Arcturus Formation. The gold mineralization is generally made up of banded or massive quartz carrying abundant coarse arsenopyrite. However, most striking is a distinct suite of Au-Bi-Te-S minerals, namely joseite-A (Bi4TeS2), joseite-B (Bi4Te2S), hedleyite (Bi7Te3), ikunolite (Bi4S3), ‘protojoseite’ (Bi3TeS), an unnamed mineral (Bi6Te2S), bismuthinite (Bi2S3), native Bi, native gold, maldonite (Au2Bi), and jonassonite (AuBi5S4). The majority of the Bi-Te-S phases is characterized by Bi/(Se+Te) ratios of >1. Accordingly, this assemblage formed at reduced conditions at relatively low fS2 and fTe2. Fluid-inclusion thermometry indicates depositional temperatures of the main stage of mineralization of up to 342°C, in the normal range of mesothermal, orogenic gold deposits worldwide. However, melting temperatures of Au-Bi-Te phases down to at least 235°C (assemblage (Au2Bi + Bi + Bi7Te3)) imply that the Au-Bi-Te phases have been present as liquids or melt droplets. Furthermore, the close association of native gold, native bismuth and other Bi-Te-S phases suggests that gold was scavenged from the hydrothermal fluids by Bi-Te-S liquids or melts. It is concluded that a liquid/melt-collecting mechanism was probably active at Viceroy Mine, where the distinct Au-Bi-Te-S assemblage either formed late as part of the main, arsenopyrite-dominated mineralization, or it represents a different mineralization event, related to rejuvenation of the shear system. In either case, some of the gold may have been extracted from pre-existing, gold-bearing arsenopyrite by Bi-Te-S melts, thus leading to an upgrade of the gold ores at Viceroy. The Au-Bi-Te-S assemblage represents an epithermal-style mineralization overprinted on an otherwise mesothermal (orogenic) gold mineralization.

K-Ar Ages of Volcanic Rocks and Gold-Bearing Quartz-Adularia Veins in the Bodie Mining District, Mono County, California

1972 ◽  
Vol 67 (5) ◽  
pp. 597-603 ◽  
Author(s):  
Miles L. Silberman ◽  
Charles W. Chesterman ◽  
Frank J. Kleinhampl ◽  
Cliffton H. Gray
Keyword(s):  
Volcanic Rocks ◽  
Mining District ◽  
Gold Bearing
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