Regional geology and tectonic framework of the Southern Indian domain, Trans-Hudson Orogen, Manitoba

The collaborative federal-provincial Southern Indian Lake project in north-central Manitoba covered an area of more than 3500 km2 of the Trans-Hudson orogen. Regional-scale geological mapping, sampling, and lithogeochemical, isotopic and geochronological studies resulted in the identification of distinct assemblages of supracrustal rocks and varied episodes of plutonism. A granodiorite gneiss dated at ca. 2520 Ma is interpreted to represent the basement of the Southern Indian domain and is considered a separate crustal domain, named the Partridge Breast block. The Churchill River assemblage is composed of juvenile pillow basalt with intervening clastic sedimentary rocks, possibly a reflection of plume magmatism related to initial rifting of the Hearne craton margin. The Pukatawakan Bay assemblage consists mainly of massive to pillowed, juvenile metabasaltic rocks and associated basinal metasedimentary rocks. The Partridge Breast Lake assemblage is dominated by continental-arc volcanic and volcaniclastic rocks associated with basinal metasedimentary rocks. The Strawberry Island assemblage, consisting of arenite and polymictic conglomerate, is interpreted to have been deposited in a foreland-basin basin or intra-orogen pull-apart basin environment. The Whyme Bay assemblage is characterized by fluvial-alluvial orogenic sediments and is temporally linked to the Sickle Group rocks in the Lynn Lake greenstone belt. Granitoid rocks, dominantly monzogranite and granodiorite, range in age from ca. 1890 to 1830 Ma and occur throughout the Southern Indian domain, and intermediate and mafic intrusions of similar ages are also present. In this paper we integrate these new data into a tectonic framework for the Southern Indian domain of the Trans-Hudson orogen in Manitoba.

Facies Architecture and Sedimentary Structures in the drill cores of Uranium Bearing Sediments of Banganapalle Formation of Palnad Sub-basin, Guntur District, Andhra Pradesh

The Banganapalle Formation, the lowest member of the Neoproterozoic Kurnool Group of rocks, resting over the basement granites, has been identified as the host rock for uranium in Koppunuru area in the western part of Palnad sub-basin. The uppermost arenite facies of the Banganapalle Formation is exposed on surface and shows only few bedform indicators like ripple marks, planer laminations etc. Down-hole lithological examinations on course of core drilling in Koppunuru and adjoining areas identified five recognizable lithofacies of Banganapalle Formation, viz. basal conglomerate unit, quartzite-shale intercalated facies, and two quartz arenite facies separated by a grey shale dominated argillaceous facies. The polymictic conglomerate, with unsorted grit to pebble size clasts of granite, shale, quartzite, vein quartz and dolerite indicate short distance transportation and derivation from nearby granitoids traversed by quartz reef/dolerite dykes. Cyclic repetitions of arenaceous and argillaceous sediments in Banganapalle lithocolumn above the basal conglomerates point to alternate rhythmic marine transgression and regression regimes. These units can also be discriminated based on their sedimentary texture, bedforms and several soft-sedimentary penecontemporaneous deformational structures (PCD) like load structure, convolute bedding/laminations, and slump structures such as micro-slips, gravity faults and folds. These syn-sedimentary structures clearly indicate perturbation and submergence of the basin contemporaneous to deposition. Cross-beds suggests change in current direction/intensity while bi-directional symmetrical ripples in outcrops of upper arenite facies suggests that the Banganapalle sediments are derived from the basement granitoids exposed to the north as well as upper Cuddapah sediments to its west. Overall, the sedimentary structures, textural and composition variation of the lithounits suggest deposition of these sediments in marginal marine, inter- to supra-tidal flat environment. The porous and permeable nature of the quartz arenite and the basal conglomerates and the presence of available reductants in the form of sulphides and carbonaceous matter make them the best suited loci for fluid movement and precipitation of uranium.

Sedimentary evolution and stratigraphy of the ~765–740 Ma Kansuki-Mwashya platform succession in the Tenke-Fungurume Mining District, Democratic Republic of the Congo

The origin of the Mwashya Conglomerate at the base of the Mwashya Subgroup in the Lufilian Belt is uncertain since it is considered as either a tectonic or as a sedimentary breccia. At Tenke Fungurume Mining District (TFMD) in the Democratic Republic of the Congo, the Mwashya Conglomerate is marked by an iron-bearing polymictic conglomerate embedded between the Kansuki and Kamoya formations. In this paper, the Kansuki-Mwashya platform succession at TFMD was investigated to shed light on the origin of this conglomerate, the depositional evolution and the tectonostratigraphic framework of the platform. Lithofacies analysis revealed that the Mwashya Conglomerate is a periglacial olistostrome, which was formed around ~765–745 Ma. A pre-Sturtian age for this conglomerate is supported by the Kamoya Formation, which is here interpreted as a post-glacial cap carbonate sequence. The Kansuki-Mwashya platform succession consists of a protected coastal lagoon adjacent to a tidal flat environment, both bordered by a barrier shoal. This paper concludes that the Kansuki-Mwashya platform succession was driven by rifting pulses, occurring gravity flows on instable slope, superimposed upon the ~750–717 Ma long-lasting Sturtian glacial period.

Proposed correlation of Oman’s Abu Mahara Supergroup and Saudi Arabia’s Jibalah Group

ABSTRACT The Ediacaran–Cambrian Middle East Geologic Time Scale is extensively revised in the 2014 version (Enclosure). It suggests the top of the Abu Mahara Group glacial diamictites in Oman represent the termination of the late Cryogenian Marinoan Glaciation at 635 Ma. The overlying Ediacaran Nafun Group of Oman is shown between 635 and 547 Ma based on geochronologic data, and divided into: (1) the Lower Nafun Supersequence (635–582 Ma) consisting of the Hadash Formation (cap carbonate), the Masirah Bay Formation (clastics) and the Khufai Formation (carbonates); and (2) the Upper Nafun Supersequence (582–547 Ma) consisting of the Shuram Formation (clastics and carbonates) and the Buah Formation (carbonates). The Nafun Group lies below the Ediacaran– lower Cambrian Ara Group (evaporites and carbonates), which contains the Ediacaran/Cambrian Boundary currently dated at 541 Ma. The Sub-Shuram Unconformity, which corresponds to the global Shuram δ13C Negative Excursion, separates the Nafun supersequences. Its age was estimated by assuming the thicknesses of the Nafun formations are proportional to time in the Masirah-1 Well, where the Nafun Group attains its greatest-known thickness of 2,308 m in Oman. This assumption coincidently estimated the unconformity at 582 Ma, the same age as the Ediacaran Gaskiers (Varanger or Varingian) Glaciation. The new calibration was used to correlate the Nafun formations to the rock-time units of the Jibalah Group in several isolated basins along the Najd Fault System in the Arabian Shield, using recently published geochronologic data and δ13C measurements, as follows. The younger part of the Lower Nafun Supersequence (635–582 Ma) is here correlated to the Lower Jibalah Supersequence (605 ± 5 to 582 Ma), represented by the Umm al-Aisah Formation in the Jifn Basin, located along the Halaban-Zarghat Fault Zone of the Najd Fault System. The Umm al-Aisah Formation consists of volcanics and clastics that give way to the Umm al-Aisah Limestone. The Upper Nafun Supersequence (582–547 Ma) is here correlated to the Upper Jibalah Supersequence, which unconformably overlies the Umm al-Aisah Limestone, with its basal unit being the Gaskiers-coeval Jifn Polymictic Conglomerate (≥ 200 m thick). In the Bir Sija Basin, located along the Rika Fault Zone of the Najd Fault System, the likely Gaskiers-coeval polymictic conglomerate (150 m thick) is overlain by a 20 m-thick limestone unit, the Bir Sija Limestone, possibly a cap carbonate. The Upper Jibalah Supersequence continues with clastics overlain by the Muraykhah Formation (carbonates) or mixed clastics-carbonates of its equivalent formations. In several outcrops the Upper Jibalah Supersequence is overlain by the lower Cambrian Siq Sandstone Formation (≤ 525 ± 5 Ma) implying the Sub-Siq Unconformity represents a hiatus between 547 and 525 ± 5 Ma. The Jifn Formation in the Jifn Basin, however, may represent continuous deposition between 582 Ma and 525 ± 5 Ma.

Quartz arenites of the Cambro-Ordovician Kamouraska Formation, Quebec Appalachians, Canada: I. Deep-water depositional processes in a continental-slope environment

The Kamouraska Formation is an uppermost Cambrian – lowermost Ordovician quartz-arenite-dominated unit of controversial origin deposited on the southeastern slope of Laurentia bordering the Iapetus Ocean. It is exposed in the Quebec Appalachians on the south shore of the St. Lawrence Estuary. The formation consists of basal polymictic conglomerate and overlying massive sheet-like quartz arenite. The conglomerate beds are reversely and reversely to normally graded. The quartz arenite beds are generally massive, although they may show coarse-tail grading. Beds containing full or partial Bouma sequences are rare. Paleoflow directions from ripple-cross lamination, ripple marks on bed surfaces, and sole marks point towards southeast, south, and southwest. The clastic sediments of the Kamouraska were transported into the deep sea by sediment gravity flows that evolved from hyperconcentrated to concentrated density flows, and then to turbidity currents. The depositional environment is interpreted to have been a southwest-trending meandering submarine canyon. The exposed part of the canyon deposits is slightly oblique to the strike of slope. If correct, our interpretation establishes the preservation of continental-slope deposits in more distal deep-water siliciclastic sedimentary rocks of the Taconian orogen in Quebec, which traditionally have been interpreted as submarine-fan and (or) basin-plain deposits. The orientation of a canyon near parallel-to strike of the slope may have been controlled by syn-depositional growth faults. The coarsest hyperconcentrated flows, which deposited the conglomerate, were restricted to the deepest parts of the canyon during its early stages of development, whereas the concentrated density flows that deposited the massive quartz-arenite beds covered a wider area.

Late Ediacaran to early Cambrian (Infracambrian) Jibalah Group of Saudi Arabia

ABSTRACT This paper is one of a series that document the Neoproterozoic – Cambrian rock units in the Middle East Geologic Time Scale. It is focused on the oldest sedimentary succession in Saudi Arabia, the late Ediacaran – early Cambrian (Infracambrian) Jibalah Group (ca. 585 to 530–520 Ma). The group crops out in disconnected, pull-apart basins (ca. 10–100 km long and up to 20 km wide) along the NW-trending, strike-slip Najd Fault System in the Arabian Shield. It was described and mapped in the 1960s to 1980s, and several formations were defined and named in two areas separated by ca. 400 km. The stratigraphic successions in these two areas have not been correlated, nor has their relationship to the subsurface been resolved. This paper reviews the nomenclature, type sections, lithologies and ages of the formations and members (sometimes units and/or facies) of the Jibalah Group. The Jibalah Group unconformably overlies the Ediacaran Shammar Group (ca. 620–585 Ma, consisting mainly of rhyolite or granitic plutons), or older Proterozoic rocks. The age of the intervening Sub-Jibalah Unconformity is here estimated at ca. 585 Ma based on radiometric data and regional correlations. The lower part of the Jibalah Group is defined in the northern Arabian Shield in the Mashhad area, where it consists of three formations, in ascending order: (1) undated Rubtayn Formation, divided informally into the “Volcanic Conglomerate Member” (up to ca. 700 m thick), “Polymictic Conglomerate Member” (up to ca. 1,500 m thick) and “Sandstone Member” (up to ca. 1,000 m thick); (2) poorly dated Badayi Formation consisting of andesite-basalt flows (ca. 150 m thick); (3) undated Muraykhah Formation (330–370 m thick) consisting of the informal “Cherty Limestone Member” (ca. 135 m thick), “Siltstone and Mudstone Member” (ca. 20 m thick) and “Dolomitic Limestone Member” (ca. 135–175 m thick). The Rubtayn, Badayi and Muraykhah formations in the northern Arabian Shield, by stratigraphic position and lithology, correspond to the Umm Al ‘Aisah Formation in the Najd pull-apart basins of the central Arabian Shield. In particular, the Cherty Limestone unit (300–500 m thick) of the Umm Al ‘Aisah Formation is correlated to the Muraykhah Formation, which represents a marine flooding event. Above the Muraykhah Formation, the uppermost part of the group is defined in the central Arabian Shield by the undated Jifn Formation (up to ca. 2,500 m thick). The Jibalah Group is unconformably overlain by the lower Cambrian Siq Sandstone Formation (Asfar Sequence), and the intervening Sub-Siq Unconformity (Angudan Unconformity) has an estimated age between ca. 530–520 Ma.

Geology of the shear-hosted Brookbank gold prospect in the Beardmore–Geraldton belt, Wabigoon subprovince, Ontario

The Beardmore–Geraldton belt consists of steeply dipping, intercalated panels of metavolcanic and metasedimentary rocks along the southern margin of the granite–greenstone Wabigoon subprovince in the Archean Superior Province, Ontario. It is an important past-producing gold belt that includes classic epigenetic iron-formation-hosted deposits near Geraldton and turbidite-hosted deposits, north of Beardmore. The Brookbank gold prospect belongs to a third group of related gold deposits that formed along dextral shear zones localized at contacts between panels of metasedimentary and metavolcanic rocks. The Brookbank prospect occurs along a steeply dipping shear zone at the contact between footwall polymictic conglomerate and hanging-wall calc-alkaline arc basalt. Early during shearing the basalt acted as a structural and chemical trap that localized brittle deformation, veining, and gold deposition, ankerite–sericite–chlorite–epidote–pyrite alteration, and the replacement of metamorphic magnetite and ilmenite by gold-bearing pyrite. This produced a low grade (≤5 g/t Au) ankerite-rich alteration zone that extends up to 20 m into the hanging-wall basalt. Later during shearing, gold was deposited within higher grade (≤20 g/t Au) quartz–orthoclase–pyrite alteration zones superimposed on the wider ankerite-rich alteration zone. Auriferous quartz–carbonate veins oriented clockwise and counter-clockwise to the shear zone walls are folded and boudinaged, respectively, consistent with dextral slip along the shear zone. A key finding of the study is that different groups of gold deposits in the belt, including epigenetic iron formation gold deposits near Geraldton, formed during post-2690 Ma regional dextral transpression across the belt.