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IntroductionDog bite is the second most common injury sustained by humans after snake bites, and it is amongst the top 12 causes of non-fatal injuries worldwide. Globally, 59,000 human deaths occur annually due to rabies, and 95% of these deaths occur in Asia and Africa. Dog bites remained a public health concern in Ghana, with three out of every 1000 incidence resulting in human rabies. Analysis of the surveillance data is key in understanding the burden of dog bites in the Volta region. This study describes the epidemiology of dog bites in the Volta Region, Ghana, to inform policy on prevention and control.MethodsWe conducted a descriptive analysis of secondary data on dog bites. We obtained aggregate data from 2015 to 2019 from the District Health Management Information System (DHMIS). Variables extracted were gender, age, and location. Data were entered into a Microsoft Excel cleaned, reviewed, and analyzed. We used descriptive statistics to summarize results into frequency and proportion and displayed results in tables, graphs, and maps.ResultsDuring the study period, 4737 dog bite cases were identified from a population of 1,907,529 (incidence of 248 per 100,000). Twelve (0.25%) humans were confirmed for rabies with a 100% case fatality rate. Males accounted for 2455 (51.8%) of dog bite cases. The age group between 10 and 19 years (21.9%) was most affected. About 35.0% (1640/4737) were administered with the anti-rabies vaccine, and 25.3% (1200/4737) were administered anti-tetanus toxoid. Keta district (550 per 100000) reported the highest incidence of dog bites. Dog bite cases were highest in the third and fourth quarters of 2016 and the first quarter of 2017.ConclusionThe incidence of dog bites and rabies was high in the Volta region. Children and adolescents were mostly affected. There was a low coverage rate of anti-rabies vaccine and anti-tetanus toxoids usage. We recommended that the Regional Health Directorates and the Regional Veterinary Department develop robust strategies to control stray or free-roaming dogs in the Volta region.

Magnetite-bearing granophyre and quartz dolerite are the evolved fractions of differentiated dolerite (diabase) sills and are an important host to Archean gold deposits because they are chemical traps for orogenic fluids. Despite their economic importance, there is a poor understanding of how melt composition, crystal fractionation, sill geometry, and depth of emplacement increase the volume of host rock that is most favorable for gold precipitation during orogenesis. We use drill core logging, whole-rock geochemistry, magnetic susceptibility, gold assay, and thermodynamic modeling data from 11 mineralized and unmineralized ca. 2.7 Ga differentiated dolerites in the Eastern Goldfields superterrane (Yilgarn craton, Western Australia) to better understand the influence of igneous and emplacement processes on gold prospectivity. Orogenic gold favors differentiated dolerites, derived from iron-rich parental magmas, that crystallize large volumes of magnetite-bearing quartz dolerite (>25% total thickness). Mineralized sills are commonly >150 m thick and hosted by thick and broadly coeval sedimentary sequences. Sill thickness is an important predictor for gold prospectivity, as it largely controls cooling rate and hence fractionation. The parental melts of gold-mineralized sills fractionated large amounts of clinopyroxene and plagioclase (possibly up to 50%) at depth before emplacement in the shallow crust. A second fractionation event at shallow levels (

Coarsely crystalline mafic rocks, commonly referred to as dolerite and diabase, make up a substantial proportion of Archean greenstone belts and are hosts to major orogenic gold deposits, yet their internal architecture and contact relationships remain poorly documented and their emplacement origins are assumed rather than supported with evidence. We present results from drill core logging of several late Archean coarsely crystalline packages from the Eastern Goldfields Superterrane of the Yilgarn Craton, Western Australia, including the Golden Mile Dolerite. These large mafic bodies comprise mostly medium- to coarsely crystalline mafic rocks, but also include a variety of other products of differentiation. The bodies range from ∼75 to 460 m thick and extend for tens of kilometers, are primarily hosted in mudstones and basalt and appear to be concordant to stratigraphy. As such, this study excludes mafic dykes and extremely thick and internally complex bodies such as the Bushveld Complex. From base to top, the internal stratigraphy generally consists of a lower unit of aphyric basalt, dolerite/gabbro and peridotite ± pyroxenite, then a voluminous middle dolerite/gabbro, and an upper quartz dolerite/gabbro, and a topmost aphyric basalt. Granophyric veins and domains are common in the upper third of the mafic body. Contacts are gradational between all lithofacies, with the exception of granophric veins, which have sharp contacts. Within this overall stratigraphic framework there is variability in the relative thickness of lithofacies, number of lithofacies, as well as repetition of some lithofacies (several examples also include basalt in the interior). In well exposed examples, the key evidence for distinguishing intrusions from extrusions is provided by the top contact. However, the top contact from these examples is ambiguous. To overcome this gap, we review the character of well-studied thick ponded lavas from the literature. Most aspects of the internal character are not unique to intrusions, although the maximum groundmass grain size (excluding granophyric veins) of the Archean examples (>3 mm) is significantly coarser than that for any known ponded lavas (≪1 mm). The ability to distinguish intrusions from extrusions has important implications for reconstructing Archean greenstone stratigraphy and mineral exploration.

Archean greenstone belts commonly consist of a stratigraphy that records subaqueous deposition capped by subaerial sedimentation, yet it remains unclear if the controls on this change were driven by horizontal or vertical processes. Clasts in conglomerates can provide important constraints on this question because they inform on the changing nature of sources. The 2.7 Ga Agnew Greenstone Belt, Yilgarn Craton, Australia, provides the ideal opportunity for such a study because it contains abundant and diverse conglomerate facies and its basal stratigraphy is well understood. This study focusses on the texture and composition of lithic clasts derived from three stratigraphic conglomerate units and their host successions. The lowermost conglomerate-bearing unit, hosted in the Vivien Formation, unconformably overlies the mafic-ultramafic lavas and intrusions of the Kalgoorlie Group (ca. 2720–2690 Ma) and is dominated by aphyric to porphyritic mafic and felsic volcanic clasts. The conformably overlying Maria Mine Formation conglomerates contain a higher proportion of felsic clasts with medium- and plutonic groundmass textures. The Vivien and Maria Mine Formations (ca. 2690–2670 Ma) are dominated by cherts, turbidites and conglomerates, and represent subaqueous sediments formed in the ring-plain surrounding an emergent volcanic island. The unconformably overlying Scotty Creek Formation (ca. 2665–2655 Ma) contains conglomerates with many plutonic felsic clasts, and is dominated by bedded and cross-bedded sandstones formed in a subaerial environment. Whole-rock geochemistry of mafic and ultramafic clasts matches the local Kalgoorlie Group rocks and indicates progressive erosion of the underlying supracrustal sequence. Undeformed conglomerates lack clasts with metamorphic foliations, indicating uplift by horizontal compression could not have been significant before ca. 2655 Ma, which is considered as the time of the first major compressional event in many published structural frameworks for the region. The systematic erosion of a felsic stratovolcano, its associated plumbing system, and any resultant upwarping of underlying sequences through vertically-driven diapirism, better explains the progressive changes observed in clast texture and composition, as opposed to horizontally-driven uplift, such as compression associated with subduction.

The thick package of ∼2.7 Ga mafic and ultramafic lavas and intrusions preserved among the Neoarchean of the Kalgoorlie Terrene in Western Australia provides valuable insight into geological processes controlling the most prodigious episode of growth and preservation of juvenile continental crust in Earth's history. Limited exposure of these rocks results in uncertainty about their age, physical and chemical characteristics, and stratigraphic relationships. This in turn prevents confident correlation of regional occurrences of mafic and ultramafic successions (both intrusive and extrusive) and hinders the interpretation of tectonic setting and magmatic evolution. A recent stratigraphic drilling program of the Neoarchean stratigraphy of the Agnew Greenstone Belt in Western Australia has provided continuous exposures through a c. 7 km thick sequence of mafic and ultramafic units. In this study, we present a volcanological, lithogeochemical and chronological study of the Agnew Greenstone Belt, and provide the first pre-2690 Ma regional correlation across the Kalgoorlie Terrane. The Agnew Greenstone Belt records ∼30 m.y. of episodic ultramafic–mafic magmatism that includes two cycles, each defined by a komatiite that is overlain by units that become more evolved and contaminated with time. The sequence is divided into nine conformable packages, each consisting of stacked subaqueous lava flows and comagmatic intrusions, as well as two sills without associated extrusions. Lavas, with the exception of intercalations between two units, form a layer-cake stratigraphy and were likely erupted from a system of fissures tapping the same magma source. The komatiites are not contaminated by continental crust ([La/Sm]PM ∼ 0.7) and are of the Al-undepleted Munro-type. Crustal contamination is evident in many units (Songvang Basalt, Never Can Tell Basalt, Redeemer Basalt, and Turrett Dolerite), as judged by [La/Sm] > 1, negative Nb and Ti anomalies, and geochemical mixing trends towards felsic contaminants. Crystal fractionation was also significant, with early olivine and chromite (Mg# > 65) followed by plagioclase and clinopyroxene removal (Mg 100 km, which has implications for exploration targeting for stratigraphically hosted ultramafic Ni and VMS deposits.

The sanctuary of Pan at Banias (to give the site its modern Arabic name) was one of the most important pilgrimage centres in Roman Palestine. The cultic origins of the sanctuary remain obscure. By ...

The Crusader Complex, part of the Agnew gold camp of the Lawlers Anticline of the Yilgarn Craton, Western Australia, is located close to or along the contact between the Lawlers Basalt and Agnew Ultramafics units. Au mineralization within the four orebodies that form the Crusader Complex is dominated by very pure Au, containing less than 1 wt.% Ag, with Au variably associated with scheelite, Bi-tellurides and minor chalcopyrite within a magnetite and titanite gangue assemblage. Hydrothermal alteration associated with this style of mineralization is characterized by increasing concentrations of Mo, Be, Li, Sn and Fe and depletions in Na, Cu, Ba, Pb, Mn, Zn, Si, and K relative to protolith concentrations; these enrichments are more typical in orebodies associated with felsic intrusive-related mineralizing systems rather than the more well-known orogenic Au deposits found elsewhere within the Lawlers Anticline (e.g. at Waroonga) and within the greater Yilgarn Craton. We propose that flexures of the contact between the Lawlers Basalt and Agnew Ultramafic units acted as conduits for Au-bearing felsic intrusive-derived fluids and generated structural traps that enhanced fluid flow. The mineralizing fluids that formed the Crusader deposits were derived from the Lawlers granitoid pluton that intruded into the study area. Enhanced fluid flow promoted interaction between hydrothermal fluids and the reactive mafic–ultramafic rock sequence, augmenting the amount of Au that was precipitated during formation of the orebodies at Crusader. The magnetite-dominated quartz- and sulfide-poor intrusion-related mineralization at Crusader contrasts sharply with other late Archean intrusion-related deposits of the Yilgarn Craton that are usually sulfide- and/or quartz-rich. This may in turn suggest that the Crusader deposit represents a new class of under-explored intrusion-derived deposits, possibly opening new mineral exploration opportunities for the Agnew region, and potentially the wider Eastern Goldfields Superterrane. Enrichments in Mo and Sn and significant depletions in Cu suggest that other parts of the Lawlers batholith may also be prospective for base metal mineralization. Integration of stratigraphic interpretation with the identification of key structural fluid pathways and the presence of felsic intrusive bodies, as presented in this study, enables the delineation of the key elements that underlie mineralization at the Crusader Complex. We propose that these key elements provide vital information for future gold exploration models that can be used within other Archean terranes and within the Eastern Yilgarn Craton in particular.

The largest Neoarchean gold deposits in the world-class St Ives Goldfield, Western Australia, occur in an area known as the Argo–Junction region (e.g. Junction, Argo and Athena). Why this region is so well endowed with large deposits compared with other parts of the St Ives Goldfield is currently unclear, because gold deposits at St Ives are hosted by a variety of lithologic units and were formed during at least three different deformational events. This paper presents an investigation into the stratigraphic architecture and evolution of the Argo–Junction region to assess its implications for gold metallogenesis. The results show that the region’s stratigraphy may be subdivided into five regionally correlatable packages: mafic lavas of the Paringa Basalt; contemporaneously resedimented feldspar-rich pyroclastic debris of the Early Black Flag Group; coarse polymictic volcanic debris of the Late Black Flag Group; thick piles of mafic lavas and sub-volcanic sills of the Athena Basalt and Condenser Dolerite; and the voluminous quartz-rich sedimentary successions of the Early Merougil Group. In the Argo–Junction region, these units have an interpreted maximum thickness of at least 7,130 m, and thus represent an unusually thick accumulation of the Neoarchean volcano-sedimentary successions. It is postulated that major basin-forming structures that were active during deposition and emplacement of the voluminous successions later acted as important conduits during mineralisation. Therefore, a correlation exists between the location of the largest gold deposits in the St Ives Goldfield and the thickest parts of the stratigraphy. Recognition of this association has important implications for camp-scale exploration.

The thick piles of late-Archean volcaniclastic sedimentary successions that overlie the voluminous greenstone units of the eastern Yilgarn Craton, Western Australia, record the important transition from the cessation in mafic-ultramafic volcanism to cratonisation between about 2690 and 2655 Ma. Unfortunately, an inability to clearly subdivide the superficially similar sedimentary successions and correlate them between the various geological terranes and domains of the eastern Yilgarn Craton has led to uncertainty about the timing and nature of the region's palaeogeographic and palaeotectonic evolution. Here, we present the results of some 2025 U–Pb laser-ablation-ICP-MS analyses and 323 Sensitive High-Resolution Ion Microprobe (SHRIMP) analyses of detrital zircons from 14 late-Archean felsic clastic successions of the eastern Yilgarn Craton, which have enabled correlation of clastic successions. The results of our data, together with those compiled from previous studies, show that the post-greenstone sedimentary successions include two major cycles that both commenced with voluminous pyroclastic volcanism and ended with widespread exhumation and erosion associated with granite emplacement. Cycle One commences with an influx of rapidly reworked feldspar-rich pyroclastic debris. These units, here-named the Early Black Flag Group, are dominated by a single population of detrital zircons with an average age of 2690–2680 Ma. Thick (up to 2 km) dolerite bodies, such as the Golden Mile Dolerite, intrude the upper parts of the Early Black Flag Group at about 2680 Ma. Incipient development of large granite domes during Cycle One created extensional basins predominantly near their southeastern and northwestern margins (e.g., St Ives, Wallaby, Kanowna Belle and Agnew), into which the Early Black Flag Group and overlying coarse mafic conglomerate facies of the Late Black Flag Group were deposited. The clast compositions and detrital-zircon ages of the late Black Flag Group detritus match closely the nearby and/or stratigraphically underlying successions, thus suggesting relatively local provenance. Cycle Two involved a similar progression to that observed in Cycle One, but the age and composition of the detritus were notably different. Deposition of rapidly reworked quartz-rich pyroclastic deposits dominated by a single detrital-zircon age population of 2670–2660 Ma heralded the beginning of Cycle Two. These coarse-grained quartz-rich units, are name here the Early Merougil Group. The mean ages of the detrital zircons from the Early Merougil Group match closely the age of the peak in high-Ca (quartz-rich) granite magmatism in the Yilgarn Craton and thus probably represent the surface expression of the same event. Successions of the Late Merougil Group are dominated by coarse felsic conglomerate with abundant volcanic quartz. Although the detrital zircons in these successions have a broad spread of age, the principal sub-populations have ages of about 2665 Ma and thus match closely those of the Early Merougil Group. These successions occur most commonly at the northwestern and southeastern margins of the granite batholiths and thus are interpreted to represent resedimented units dominted by the stratigraphically underlying packages of the Early Merougil Group. The Kurrawang Group is the youngest sedimentary units identified in this study and is dominated by polymictic conglomerate with clasts of banded iron formation (BIF), granite and quartzite near the base and quartz-rich sandstone units containing detrital zircons aged up to 3500 Ma near the top. These units record provenance from deeper and/or more-distal sources. We suggest here that the principal driver for the major episodes of volcanism, sedimentation and deformation associated with basin development was the progressive emplacement of large granite batholiths. This interpretation has important implication for palaeogeographic and palaeotectonic evolution of all late-Archean terranes around the world.

Granite-cored domes are associated with many of the larger gold deposits of the Archaean Eastern Yilgarn Craton of Western Australia. The Scotia-Kanowna Dome is eroded to sufficiently deep levels to provide insights into the role granite-cored domes play in controlling fluid flow and gold deposition. At the centre of the Scotia-Kanowna Dome is a granite batholith, which is surrounded by outward-dipping greenstone belts and associated shear zones. This upper-crustal dome sits above mid-crustal domes, providing a series of stacked geometries favourable to focussed fluid flow. A number of small- to medium-sized gold deposits occur on the limbs and the centre of the dome, and the world-class Kanowna Belle gold mine occurs on the nose of the dome. At least three separate gold mineralising events are defined, each of regional significance, which can be correlated with other well known gold deposits of the Eastern Yilgarn Craton. The palaeostress across this region was dominated by both maximum contractional and extensional vectors oriented perpendicular to the north-northwest trending grain. The resultant strain is seen in the architecture of the Scotia-Kanowna Dome, with its margins and associated shear zones controlling the distribution of stratigraphy, which is relatively linear and parallel to the margin. Throughout most of the tectonic history, the flanking shear zones were high-strain domains that recorded multiple stages of contraction, with thrust and mostly sinistral strike-slip shear kinematics. In contrast, the dome nose region was a relatively low-strain domain as it was located in the strain shadow of the regional contractional events. For example, the early extensional record has been preserved at the nose, with late-stage basins formed in the hangingwall to the extensional faults, adding to the stratigraphic complexity of the local region. These late basins also may have contributed to the fluid budget. In contrast, along the flanks of the domes there is no record of these late basins or the extensional faults that controlled their deposition. The architecture of the dome played an important role in controlling mineralisation during a significant deviation in the maximum contractional stress vector to an east-southeast-west-southwest orientation. At this time, basins in the nose region underwent inversion, with thrusting to the north and northwest. Shortening was accommodated along the dome flanks by sinistral strike-slip shearing, which was relatively free to move due to the mostly linear stratigraphy, combined with limited anisotropy and perturbations along the flank. However, the stratigraphic and geometrical complexity around the dome nose resulted in localised maximum dilation and gold deposition at this time. The dome nose area was also a favoured locus for gold-enriched, dominantly Mafic-type magmas, which are seen as the extensive porphyry swarms in the region. These felsic-intermediate rocks also may have contributed to the complex fluid budget and are considered as indicators of particular fertility for gold. They may have been the primary source for much of the metal endowment. The architecture of granite-cored domes has played a critical role in focussing magma as well as mineralising fluids into regions of maximum dilation. They did this by virtue of their inherent competence, and by influencing the position and geometry of shear zones (fluid pathways) and hence distribution of stratigraphy (depositional sites) across the region. The Scotia-Kanowna Dome is a good example of this effect, and inferences can be made in favour of similar controls by concealed domes, such as beneath Kalgoorlie.

A new structural evolution consisting of both extensional and contractional events has been defined for the St Ives Goldfield in the south-central Kalgoorlie Terrane of the eastern Yilgarn Craton in Western Australia. These events shaped the development of the fault architecture, which controlled the location of the regional anticlines, the magmatic centres, and the deposition of the Archaean greenstone successions. The fundamental grain of the St Ives Goldfield is north-northwest-trending. This trend is marked by faults which developed during D1 extension, which was oriented east-northeast–west-southwest. Across these faults we map major stratigraphic changes in the thickness and composition of units, especially of the previously undivided Black Flag Group volcaniclastic rocks. The centre of the St Ives Goldfield is dominated by the Kambalda Anticline. This north-northwest-trending regional fold was likely established early during the D1 extensional history, and was fully established during subsequent east-northeast-oriented D2 contraction. The regional anticline is an important architectural element because (1) magmatism and gold mineralising fluids were focussed into this domed region, and (2) deformation was partitioned across the limbs and crest of this structure. The D3 event involved regional uplift and extension, resulting in the formation of late basins (Merougil Conglomerate locally) and the emplacement of granitoids sourced from a metasomatised mantle wedge (Mafic-type porphyries). The most significant gold event in terms of endowment occurred during D4b sinistral strike-slip shearing and associated thrusting (e.g., Tramways and Republican thrusts). These thrusts were previously interpreted as the first contractional structures to deform the area (‘D1’), but are here reinterpreted as relatively late (D4b). In this D4b event, the north-northwest-trending faults underwent sinistral strike-slip shearing and were linked across the Kambalda Anticline by accommodation structures represented by generally east- to east-northeast-trending thrusts. Reactivation of D1 transfer structures may have influenced the location of these later accommodation structures. Late-stage mineralisation during D5 was the result of dextral strike-slip brittle shearing.

The consensus view is that the O 2 concentration of the Archean atmosphere was very low and that it rose to its present level of 21% in a series of steps, two of which dwarf the others in importance. The first, known as the Great Oxidation Event, occurred at ∼2.4 Ga. It involved an increase in the relative abundance of O 2 , which has been estimated at three orders of magnitude, and it is important because it led to the first surface weathering. The second, although less important in relative terms, involved the addition of 9 × 10 17 kg of O 2 to the atmosphere, at least ten times as much as that required to produce the Great Oxidation Event. Its importance lies in the fact that it correlates with the rise of animals in the Ediacaran and Early Cambrian periods. Although it is widely accepted that an increase in atmospheric O 2 facilitated the appearance of animals at ∼575 Ma, followed by the Cambrian Explosion ∼50 Myr later, the cause of this increase remains controversial. We show that the surge in the O 2 level near the Precambrian–Cambrian boundary correlates with major episodes of continent–continent collision associated with Gondwana’s amalgamation, including convergence between East and West Gondwana, which produced the 8000-km-long Transgondwanan Supermountains. The eroded roots of these mountains include the oldest lawsonite-bearing blueschists and eclogites, and ultra high-pressure metamorphic rocks. The sudden appearance of these low-thermal gradient, high-pressure metamorphic rocks implies that the Gondwanan orogenic zones were cooler and stronger than those associated with the assembly of earlier supercontinents and therefore capable of supporting higher mountains. There is a log-linear relationship between relief and erosion rate, and a linear relationship between sedimentation rate and organic C burial. Taken together these two relationships imply a log-linear relationship between relief and C sequestration. We suggest that the Gondwanan supermountains were higher than those produced during the assembly of earlier supercontinents and that rapid erosion of these mountains released a large flux of essential nutrients, including Fe and P, into the rivers and oceans, which triggered an explosion of algae and cyanobacteria. This, in turn, produced a marked increase in the production rate of photosynthetic O 2 . Rapid sedimentation during this period promoted high rates of burial of biogenic pyrite and organic matter generated during photosynthesis so that they could not back react with O 2 , leading to a sustained increase in atmospheric O 2 .

The ability to effectively target ore shoots requires a clear understanding of the numerous parameters that control their formation. However, identification of the nature and timing of these parameters is difficult, particularly in polydeformed deposits with complex stratigraphic and hydrothermal histories. For example, ore shoots at Stawell gold mine’s Magdala gold deposits in southeastern Australia are hosted by rocks that experienced at least three ductile and two brittle deformation events in the 70 m.y. prior to the principal mineralization event, and have a close spatial relationship to strongly chlorite ± stilpnomelane–altered sedimentary units near the apex of numerous >5-m-thick reentrant basalt lobes. Whereas the ore shoots at Stawell are located only on the southwestern flank of the 1-km-thick Magdala basalt, about 15 km along strike at the Wildwood prospect the ore shoots are predominantly restricted to the northeastern flank of the basalt. Here, the important issue of controls on ore shoot formation and distribution at Stawell is addressed by presenting the results of a multidisciplinary review of the characteristics and architecture of the volcanic and sedimentary facies, the spatial distribution of alteration assemblages, and the variations in intensity and vergence relationships of the cleavages associated with ductile deformation. This investigation, undertaken at both a regional and shoot scale, shows that the structures hosting the ore shoots at Magdala formed during preferential and localized reactivation of preexisting faults following rotation of the stress field. Preexisting structures, such as Central Lode fault, host many of the ore shoots and were initially generated during east-northeast–west-southwest compression at ca. 510 to 488 Ma. The geometries of these faults were also influenced by the irregular paleotopography of the basalt lobes, which represent flows of pillow and massive basalt separated by interflow sedimentary units. Coincident with this deformation, locally intense chlorite ± stilpnomelane alteration indurated the mud-rich units between the basalt flow-lobes and the Central Lode-type structures. Those thick, mud-rich sedimentary units are present on the southwestern flank of the basalt at Stawell, but predominantly near the top and on the northeastern flank at Wildwood. The switch to east-west compression at ca. 440 Ma caused localized failure and focusing of mineralized fluids in the indurated sedimentary rocks near the apex of the northwest-plunging portions of the basalt lobes. A second, subordinate mineralizing event at ca. 425 to 420 Ma utilized the same architecture under a different stress regime. During both mineralizing events, the high-grade ore shoots formed in zones of high fluid flow defined by the complex preexisting architecture.

Some published tectonic reconstructions of the eastern Lachlan Orogen in New South Wales have shown Ordovician volcanic and volcaniclastic rocks of the Macquarie Arc conformably overlying or interfingering with a coeval Ordovician quartz-rich turbidite sequence. Re-examination of key contacts between the volcanic and quartz-rich successions has found no evidence to support this interpretation, and suggests that the two packages are separate tectonostratigraphic terranes. The contacts between these two coeval successions are generally marked by major faults containing mylonites, cataclasites and, at some locations, fragments of mid-ocean ridge-type pillow basalt and chert. The quartz-rich turbidites are generally highly deformed and of higher metamorphic grade than the adjacent volcanics. At Oberon and Mudgee, contacts are faulted but there are no mylonites or significant differences in metamorphic grade. At Palmers Oaky and Black Springs, Silurian quartz-rich sandstones overlying the Ordovician volcanics ...

The Ordovician to Lower Silurian Forest Reefs Volcanics in the Cadia – Neville region, northeastern Lachlan Orogen, represent the product of at least two shoshonitic volcanic centres intercalated with a volcaniclastic apron. The two episodes of shoshonitic volcanism in the Forest Reefs Volcanics are separated by between 15 and 20 million years. The Forest Reefs Volcanics are informally divided into lower and upper parts, separated by an inferred unconformity that broadly coincides in age with a limestone-forming hiatus in volcanism (449 – 447 Ma) and emplacement nearby of medium-K calc-alkaline dacitic intrusions (448 – 445 Ma). The lower part includes shoshonitic basaltic andesite, feldspar-rich sandstone, volcanic lithic breccia and lesser black mudstone; polymictic volcanic conglomerate with sandstone matrix and calcareous sandstone are important near the top. The basaltic facies association occurs near the base of the lower Forest Reefs Volcanics and could represent a submarine basaltic volcano at lea...

Early Ordovician (Phase 1) magmatism in the Macquarie Arc was followed by a magmatic hiatus of ∼9 million years, between late Bendigonian and early Darriwilian (i.e. between ca 475 and ca 466 Ma). Resumption of magmatism in the Middle Ordovician produced Phase 2 rocks, recorded by three major rock suites: (i) medium-K calc-alkaline lavas in the Cargo block (Molong Volcanic Belt) have primitive Nd values (+6.9 to +7.8) and volcanic facies suggesting eruption in an intra-oceanic arc stratovolcano; lavas in the fault-bounded Parkes Volcanics in the Junee – Narromine Volcanic Belt are compositionally identical to those in the Cargo block, suggesting that similar Phase 2 Middle Ordovician arc-type lavas may underlie the Cowra Trough; (ii) medium- to high-K dioritic to monzodioritic intrusions in the Narromine and Cowal Igneous Complexes of the Junee – Narromine Volcanic Belt have ages that cluster in the 470 – 460 Ma interval, and intrude presumed Phase 1 lavas and volcaniclastics; and (iii) in all three main ...

The present study is concerned with the effect of alloying additions (e.g. Co, Nb, Pd, La and Y) to the glass forming ability (GFA) of Al-Y-Ni alloys. Rapidly solidified ribbons of the following systems have been prepared by melt-spinning process: Al 88 Ni x / 2 Pd x / 2 Y 12-x (x=2, 5, 10), Al 88 Ni 1 Co 1 Y 10-x La x (x=0, 5, 10), Al 88 Ni 1 Nb 1 Y 10 , and Al 86 Ni 4-x Co x Y 10 (x=1, 2, 3). Characterisation of the melt spun alloys was carried out through a combination of X-ray diffractometry, differential scanning calorimetry, and transmission electron microscopy. GFA in Al 88 Ni 1 TM 1 Y 10 (where TM = Co, Nb, Pd) increases in the following order: Nb < Co < Pd. To maintain a fully amorphous structure in Al 88 -Ni-Pd-Y systems the optimum quantity of yttrium is 10 at.%. A complete substitution of Y with La, or aluminium with 2 at.% of (Co,Ni) decreases the glass forming ability in Al 88 Ni 1 Co 1 Y 10 but increases thermal stability of the residual amorphous phase. Partial replacement of Y with La significantly improves the thermal stability of the amorphous phase in Al-Ni-Co-Y.

The Ordovician volcanic and intrusive rocks of the Cadia – Neville region, in the southern Molong Volcanic Belt section of the Macquarie Arc in central-western New South Wales, display a temporal progression from shoshonitic basaltic volcanism (e.g. Mt Pleasant Basalt Member) in the late Darriwilian to Gisbornian (ca 460 – 453 Ma) to small-volume dacitic medium-K calc-alkaline magmatism (e.g. Copper Hill-type dacite) in the late Eastonian to early Bolindian (ca 450 – 445 Ma) to large-volume, high-K calc-alkaline to shoshonitic, mafic to highly evolved magmatism (e.g. Nullawonga Latite Member and Cadia Intrusive Complex) at about 445 – 440 Ma. The two episodes of shoshonitic magmatism are separated by at least 15 (but up to ∼20) million years, during which time limestones, associated with regional uplift, were deposited broadly coincident with emplacement of the medium-K calc-alkaline dacitic intrusions. Despite this, the lavas and intrusions associated with both episodes of shoshonitic magmatism have stri...

Since Ebola Virus Disease (EVD) was first identified in 1976 in what is now the Democratic Republic of Congo, and despite the numerous outbreaks recorded to date, rarely has an epidemic origin been identified. Indeed, among the twenty-one most documented EVD outbreaks in Africa, an index case has been identified four times, and hypothesized in only two other instances. The initial steps of emergence and spread of a virus are critical in the development of a potential outbreak and need to be thoroughly dissected and understood in order to improve on preventative strategies. In the current West African outbreak of EVD, a unique index case has been identified, pinpointing the geographical origin of the epidemic in Guinea. Herein, we provide an accounting of events that serve as the footprint of EVD emergence in Sierra Leone and a road map for risk mitigation fueled by lessons learned.

The explosive radiation of animals on Earth during the late Early Cambrian period (∼ 530–510 Ma) coincides with the deposition of enormous volumes of continentally derived sedimentary rocks throughout Gondwana. We show here, that these quartz-rich sedimentary units, collected from five continents, display remarkably similar detrital-zircon U–Pb age-patterns and propose that they were sourced from either side of a > 8000-km-long and generally > 1000-km-wide mountain chain (the Transgondwanan Supermountain), which formed following oblique collision between East and West Gondwana, commencing at ∼ 650 Ma. The depositional system supplied by this mountain chain was > 100 km3, which is equivalent to covering all 50 states of the USA with ∼ 10 km of sediment, and it lasted for at least 260 Myr. The enormous size of the vegetation-free mountain chain, its position close to the equator and the dramatic changes in global plate-motion in response to the cessation in continent–continent collision, together with the possible appearance of biota in the soils that promoted rapid chemical weathering, resulted in extreme erosion and sedimentation rates that are arguably the highest in the geological record. This led to an unprecedented flux of P, Fe, Sr, Ca and bicarbonate ions into the oceans. The addition of Sr was responsible for seawater 87Sr/86Sr building up to the highest levels in Earth's history, whereas the addition of P and Fe provided the essential nutrients that supported a bloom of primitive life that in turn provided abundant food to support the Cambrian explosion of life. The addition of Ca and bicarbonate ions increased CaCO3 supersaturation in the oceans, which allowed species in numerous phyla to simultaneously develop skeletons.

The paucity of microfossils in the Cambrian volcanic and sedimentary succession west of the Avoca Fault in western Victoria is generally attributed to their low preservation-potential in the polydeformed and highly altered early Palaeozoic host rocks. The resulting lack of biostratigraphic age control has made temporal correlations between Cambrian successions difficult, leading to a relatively poor understanding of the Cambrian palaeogeographic and palaeotectonic evolution of the region. Here, we present evidence of a diverse range of acritarchs and a rare possible conodont from siliceous mudstone (chert) of the middle Botoman (ca 515 Ma) Albion Formation at Stawell and the middle Middle Cambrian (ca 505 Ma) Glenronald Shale Member near Mt Stavely. Acritarchs are polyphyletic organisms that include the vegetative and resting cysts of unicellular protists, mainly phytoplankton, which underwent rapid diversification during the Early Cambrian. The morphologically heterogeneous populations of Early Cambrian ...

The Hangingwall reefs are high-grade auriferous quartz lodes that occur in the upper levels of the Magdala mine at Stawell, and thus represent an important deposit style in western Victoria. Structural relationships indicate that the Hangingwall Reefs formed coincident with the same metallogenic event that produced the adjacent Magdala deposit. However, the host-rocks to the quartz – gold veins that make up the Hangingwall Reefs display markedly different structural and stratigraphic relationships. Hangingwall Reef mineralisation occurred during east – west shortening in a muscovite-altered turbidite sequence that had little prior iron alteration (cf. Magdala deposit). Lithological and structural data show that the distribution of the quartz – gold veins is related to the geometry of the Stawell Fault and its associated fault splays, with the quartz veining being localised where the faults are discordant with the pre-existing structural fabrics. This discordant relationship produced the dilational sites a...

Lower Cambrian basalts in the Stawell Zone (e.g. Magdala Basalt) are intercalated with a thick package of continentally derived quartz-rich turbidites, whereas similar basalts in the Heathcote and Mt Wellington Greenstone Belts are underlain by broadly coeval boninites and overlain by Upper Cambrian cherts. These marked differences in the magmatic – stratigraphic associations of the Early Cambrian basalts in Victoria have led to highly varied interpretations of their tectonic setting, which include subduction zones that are east-dipping, west-dipping and even a combination of east- and west-dipping systems. Here, we present new geochemical data for Cambrian basalts from the Stawell Zone and reassess the palaeogeographic and palaeotectonic setting of the region. Our geochemical data show that basalts in the Stawell Zone may be broadly divided into two units: basalts that are LREE-depleted relative to N-MORB and have low (≤3.0 ppm) Nb contents; and basalts that are slightly LREE-enriched relative to N-MORB ...

The Magdala deposit in the Stawell goldfield in western Victoria was formed during the 440 Ma gold event of the Lachlan Orogeny and is hosted by Cambrian quartz-rich turbiditic sedimentary rocks (Albion Formation) that onlap a thick pile of tholeiitic basaltic lavas (Magdala Basalt). Detailed petrographic and geochemical analyses suggest that the host-rock (Stawell Facies) was originally a turbiditic sedimentary rock that was hydrothermally altered in response to seawater interaction with the hot basaltic pile. Subsequent regional greenschist metamorphism and ductile deformation that lasted at least 10 million years culminated in the formation of the Magdala mineralised system and produced a complex pattern of hydrothermal alteration. Evolution of this alteration occurred over six stages: Stage 1, Fe-enrichment of sedimentary rock adjacent to the basalt pre-D1; Stage 2, chlorite (metamorphism), orbicular carbonate and pyrite, syn-D2; Stage 3, muscovite, siderite, ankerite and pyrrhotite, syn-D3 – D4a – b;...

The early Palaeozoic Macquarie Arc, southeastern Australia, hosts a variety of major late Ordovician to earliest Silurian subduction-related deposits (e.g., Cadia East, Ridgeway, Cadia Hill, Cowal and Northparkes). However, there is uncertainty about whether coeval high-sulfidation epithermal deposits, which occur in intra-oceanic metallogenic belts elsewhere in the West Pacific, (e.g., Lepanto and Chinkuashih), are also present in the Macquarie Arc. This has led to suggestions that their absence may be due to the poor preservation potential of deposits that form at relatively shallow crustal levels in ancient rocks. We present here an interpretation for evolution of the Peak Hill Au–Cu deposit based on the distribution of alteration facies, sulfur isotope data from several textural forms of pyrite and barite, and an assessment of the regional volcanic and sedimentary facies architecture. These data show that the Peak Hill deposit displays a distinct sub-vertical zoning with a pyrophyllite and vuggy-quartz core, that today extends about 350 m east–west and at least 550 m north–south, which grades out through paragonite+muscovite, kaolinite to a chlorite+epidote alteration zone at the margin. The alteration zoning reflects both lower temperatures and neutralisation of acid fluids with increasing distance from the core, which represents the conduit along which hot acidic hydrothermal fluids were channelled. Several temporally overlapping events of silicification, bladed-quartz-pyrite veining, brecciation and pyrite veining occurred during the last stages of hydrothermal alteration, although most appear to predate mineralisation. Au–Cu mineralisation was associated with late quartz-pyrite-barite veins, and the highest gold grades occur mainly in microcrystalline-quartz-altered rocks in the paragonite+muscovite alteration zone, generally within 50 m outward from the boundary of the pyrophyllite and vuggy-quartz core. Sulfur- and lead-isotope data, and the characteristic zoning of ore minerals and alteration assemblages support a magmatic source for the hydrothermal fluids. Similarities in many of the isotopic signatures between Peak Hill and deposits such as Northparkes support generation of the high-sulfidation mineralisation during the Late Ordovician to earliest Silurian (possibly ca. 440 Ma) metallogenic event. The Late Ordovician to Early Silurian volcanic and sedimentary facies associations at Peak Hill are consistent with alteration and mineralisation occurring in rocks deposited in a submarine setting.

Difficulties in correlating the Cambrian magmatic, depositional, structural and metamorphic events along the proto-Pacific margin of East Gondwana have led to subdivision of the region into the Delamerian, Lachlan and Tyennan Orogens in Australia, the Ross Orogen in Antarctica and the Takaka Terrane in New Zealand. As a result, the Cambrian tectonic evolution of the region is poorly understood. We present here a revised lithostratigraphic section from the late Early to Mid-Cambrian rocks exposed near Stawell in western Victoria, which is used as the basis for correlating geological events in East Gondwana. These data show that the Cambrian tectonic evolution of East Gondwana9s >4000 km long proto-Pacific margin involved predominantly compressional orogenesis separated by major short-lived extensional events at c . 516–514 and 504–500 Ma. The most significant extensional event, at c . 516–514 Ma, involved extensive slab rollback along the proto-Pacific margin in response to major changes in global plate motions and plate-boundary stresses following the termination of East–West Gondwana collision. Partial subduction of a ribbon of buoyant continental crust led to localized subduction-zone failure and obduction of the young hot forearc lithosphere in Tasmania at c . 510 Ma. Collision of the continental ribbon also significantly modified the architecture of the proto-Pacific margin and ultimately controlled the extent of the second major extensional event associated with slab rollback at c . 504–500 Ma. Tectonic evolution of the proto-Pacific margin of East Gondwana thus involved the complex interaction between convergent-margin processes and collisional orogenesis.

Peperite involving basalt and polymictic volcanic conglomerate occurs in the Pliocene Ba Volcanic Group at Yaqara in northern Viti Levu, Fiji. Because the host sediment is coarse-grained and dominated by basalt clasts, the peperite could be easily overlooked and mistaken for another coarse volcaniclastic facies. However, the presence of groups of basalt clasts that show jigsaw-fit texture, fluidally shaped basalt clasts with complete glassy margins, gradational contacts with adjacent sedimentary facies and the absence of stratification indicate that molten basalt mingled with unconsolidated gravel. Using these criteria, we show that other superficially similar, coarse, polymictic facies with fluidal basalt clasts are not peperite. Both blocky and fluidal basalt clasts occur together in the peperite. The amoeboid basalt clasts in the fluidal peperite result from dismembering of ductile, low-viscosity, relatively hot magma. At this stage, propagating magma lobes were probably insulated from direct contact with the wet sediment by a vapour film. The angular, polyhedral basalt clasts in the blocky peperite indicate brittle disintegration of somewhat cooler, higher-viscosity magma. The presence of jigsaw-fit texture and polyhedral clasts with glassy margins suggest that quench fragmentation of the basalt was important in the formation of the blocky peperite. Although there is no positive evidence for steam explosivity, the presence of steam could be recorded by small quartz-filled cavities that occur within the host sediment. The co-existence of fluidal and blocky basalt clasts is interpreted to reflect successive ductile then brittle fragmentation of intruding magma. The change from fluidal to blocky peperite might have resulted from progressive cooling of the magma during intrusion, and also from the breakdown of fluidisation when the limited supply of fine sediment in the host gravel was exhausted.

The Lunnon Basalt is an Archaean, subaqueous, tholeiitic metabasalt succession, with a minimum inferred thickness of 1750 m. It forms the oldest exposed stratigraphic unit at Kambalda in the nickel sulfide‐rich Norseman‐Wiluna Greenstone Belt, Western Australia, and is dominated by variable proportions of massive basalt, pillow basalt, and basalt breccia. These facies form intimately inter‐layered massive, pillow and complex lava flow units, with an average thickness of about 20 m. The stratigraphy of the basalt can be subdivided into a ‘lower’ MgO‐rich member and an ‘upper’ less MgO‐rich member, these being separated by a sedimentary horizon. Of the possible palaeovolcanic and tectonic settings (layer 2 of oceanic crust, a large shield volcano, or a tectonically‐topographically ponded sea‐floor lava field), the Lunnon Basalt appears to be the remains of a ponded (?rift) lava succession. The presence of inherited zircon xenocrysts indicates that the subjacent crust at the time of formation was sialic, Arc...

The dramatic increase in diversity of animals between about 530 and 510 million years ago (i.e., the Cambrian explosion), coincides with the deposition of enormous volumes of continentally derived sedimentary rocks throughout Gondwana. These early Palaeozoic quartz-rich sedimentary units generally display remarkably similar U–Pb detrital-zircon age patterns, despite their present-day distribution in at least seven different countries on four different continents. The striking correlation between the detrital-zircon age spectra for these quartz-rich sedimentary units and the rocks from the East African–Antarctic Orogen, which stetched from the Arabian–Nubian Shield through East Africa to Antarctia, clearly shows that the detritus was derived from the mountains that developed along this long collisional zone. The >8000-km-long and generally >1000-km-wide East African–Antarctic Orogen formed following collision between East and West Gondwana from 650 Ma and is large enough to supply the huge volume of quartz-rich detritus dispersed over such a remarkably large areal extent. Here, we refer to the surface expression of this collisional zone as the Transgondwanan Supermountain to emphasise its palaeogeographic significance. The depositional system supplied by this mountain chain was >100 km (i.e., equivalent to covering all 52 contiguous states of the USA with >10 km of sediment) and lasted at least 260 million years. The enormous size of the mountain chain, it position close to the equator, the absence land plants and possibly the appearance of biota in the soils that promoted rapid chemical weathering, resulted in extreme erosion and sedimentation rates that are arguably the highest in the geological record. This led to an unprecedented flux of P, Fe, Sr, Ca and bicarbonate ions into the oceans. The addition of Sr was responsible for seawater Sr/Sr building up to the highest levels in Earth’s history, the addition P and Fe provided the essential nutrients that supported a bloom of primitive life, which in turn provided abundant food to support the Cambrian explosion of life, and the addition Ca and bicarbonate ions increased CaCO3 supersaturation in the oceans which allowed species in numerous phyla to simultaneous develop skeletons.

The collision of a seamount or microcontinental block with an arc may produce complex strain distributions and changes in the tectono-magmatic setting. Slab rollback and associated upwelling of asthenosphere occurred ca. 440 Ma near the margin of East Gondwana in response to subduction zone lock-up following arc collision ca. 455 Ma. World-class porphyry copper gold deposits (e.g., Cadia) formed in the backarc during extension and magmatism associated with slab rollback. Upwelling of the asthenosphere also provided the heat engine for generation of hydrothermal fluids. The result was elevated fluid pressures and compressional brittle deformation associated with orogenic gold mineralization (e.g., Bendigo) inboard of the East Gondwana margin.