Age, correlation, and provenance of the neoproterozoic skelton group, Antarctica: grenville age detritus on the margin of east Antarctica

Detrital zircon U‐Pb ages constrain the age and provenance of the Skelton Group in southern Victoria Land, one of several Proterozoic‐Cambrian metasedimentary units that form basement to the Ross Orogen in East Antarctica. The age of the youngest detrital zircons combined with previous dating of crosscutting intrusive rocks indicates deposition of the northern and southern parts of the Skelton Group between ca. 1050–535 and ca. 950–551 Ma, respectively. Many zircons in the northern part of the Skelton Group crystallized after partial melting during upper amphibolite facies metamorphism at ca. 505–480 Ma, although older ca. 550‐Ma metamorphic zircon rims indicate an earlier episode of high‐grade metamorphism. Detrital zircon ages from the Skelton Group are dominated by ca. 1300–950‐Ma ages similar to those in the Beardmore Group in East Antarctica and the Adelaidean succession of South Australia, suggesting that these rocks are generally correlative. Zircons that crystallized at ca. 1050 Ma form the major age population of the northern Skelton Group, while a broader range of Neoproterozoic zircons form significant components in other sediments deposited on the margin of East Antarctica–Australia at this time, indicating a close proximity to exposed Grenville age crust. Inferred basement rocks of Grenville age beneath the Ross Orogen in East Antarctica (represented by a potential 1049 ± 11‐Ma orthogneiss), Paleozoic cover in eastern Australia, and ice in Marie Byrd Land in West Antarctica are potential sources for the Grenville age component in these Neoproterozoic sedimentary rocks

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Geology of the plutonic basement rocks of Stewart Island, New Zealand

Exposures of basement rocks on Stewart Island provide a c. 70 km long by 50 km wide map of part of the Median Batholith that spans the margin of the Western Province. Because of their distance from the present plate boundary, these rocks are relatively unaffected by Cenozoic tectonism, allowing examination of unmodified Carboniferous–Cretaceous relationships within the Median Batholith. Thirty individual plutons (>c. 20 km2) have been mapped along with numerous relatively small intrusions ( biotite (c. 23%); gabbro and anorthosite (c. 12%) and ultramafic rocks (c. 2%). U-Pb zircon and monazite dating indicates that c. 12% of these plutonic rocks were emplaced during the Carboniferous between 345 and 290 Ma, c. 20% in the Early–Middle Jurassic at c. 170–165 Ma, c. 30% in the latest Jurassic to earliest Cretaceous between 152 and 128 Ma, and c. 38% in the Early Cretaceous between 128 and 100 Ma. The distribution of Pegasus Group schists and peraluminous granitoid rocks indicates that the northern limit of extensive early Paleozoic Western Province basement is located either within the Gutter Shear Zone or at the Escarpment Fault, 10–15 km south of the Freshwater Fault System previously thought to mark this boundary. Carboniferous and Middle Jurassic magmatism extended plutonic basement northwards as far as the Freshwater Fault System, while further magmatism during the latest Jurassic and earliest Cretaceous produced the basement north of the Freshwater Fault System. The focus of Early Cretaceous plutonism then returned southwards into the Western Province, although the older basement in this area was only involved in the genesis of subordinate peraluminous plutonism at this time and not the more extensive metaluminous rocks. The Escarpment Fault disrupted this c. 40 km wide section across the margin of the Western Province at c. 110–100 Ma.

Geology of the plutonic basement rocks of Stewart Island, New Zealand

Exposures of basement rocks on Stewart Island provide a c. 70 km long by 50 km wide map of part of the Median Batholith that spans the margin of the Western Province. Because of their distance from the present plate boundary, these rocks are relatively unaffected by Cenozoic tectonism, allowing examination of unmodified Carboniferous–Cretaceous relationships within the Median Batholith. Thirty individual plutons (>c. 20 km2) have been mapped along with numerous relatively small intrusions ( biotite (c. 23%); gabbro and anorthosite (c. 12%) and ultramafic rocks (c. 2%). U-Pb zircon and monazite dating indicates that c. 12% of these plutonic rocks were emplaced during the Carboniferous between 345 and 290 Ma, c. 20% in the Early–Middle Jurassic at c. 170–165 Ma, c. 30% in the latest Jurassic to earliest Cretaceous between 152 and 128 Ma, and c. 38% in the Early Cretaceous between 128 and 100 Ma. The distribution of Pegasus Group schists and peraluminous granitoid rocks indicates that the northern limit of extensive early Paleozoic Western Province basement is located either within the Gutter Shear Zone or at the Escarpment Fault, 10–15 km south of the Freshwater Fault System previously thought to mark this boundary. Carboniferous and Middle Jurassic magmatism extended plutonic basement northwards as far as the Freshwater Fault System, while further magmatism during the latest Jurassic and earliest Cretaceous produced the basement north of the Freshwater Fault System. The focus of Early Cretaceous plutonism then returned southwards into the Western Province, although the older basement in this area was only involved in the genesis of subordinate peraluminous plutonism at this time and not the more extensive metaluminous rocks. The Escarpment Fault disrupted this c. 40 km wide section across the margin of the Western Province at c. 110–100 Ma.

Plutonic rocks of the Median Batholith in southwest Fiordland, New Zealand: field relations, geochemistry, and correlation

This paper provides a first description of all major plutonic rock units between Resolution Island and Lake Poteriteri in southwest Fiordland. Plutonic rocks, of which c. 95% are granitoids, comprise c. 60% of the basement in southwest Fiordland. Approximately 50% of the plutonic rocks were emplaced between c. 355 and 348 Ma, 5% at c. 164 Ma, 25% between c. 140 and 125 Ma, and 20% between c. 125 and 110 Ma. These episodes of plutonism occurred in response to terrane amalgamation, continental thickening, and subduction along the convergent margin of Gondwana. Correlatives of Devonian plutonic rocks which occur in Nelson are absent from the area described here.\ud \ud A wide variety of plutonic rocks were emplaced at c. 355–348 Ma. These include relatively small plutons of K- and Rb-rich gabbro-diorite and members of at least three distinct suites of granitoids. Plutons of two-mica ± garnet granodiorite, granite, and minor tonalite share affinities with the S-type Ridge Suite and are the most widespread c. 355–348 Ma old granitoids in southern Fiordland. Plutons rich in Ca, Fe and Zr, depleted in K and Na, and containing quartz diorite, tonalite, and minor granodiorite with the unusual assemblage red-brown biotite, garnet ± hornblende ± clinopyroxene also occur widely in southern Fiordland. These plutons are similar to peraluminous A-type granitoids, indicating A as well as I and S-type plutonism occurred in the Western Province at this time. The Newton River and Mt Evans Plutons have no correlatives amongst c. 355–348 Ma granitoids in southern Fiordland, but their chemistry is similar to that of the older Karamea Suite.\ud \ud Three regional-scale metasedimentary units—locally fossiliferous Fanny Bay Group Buller Terrane rocks in southern Fiordland, Edgecumbe and Cameron Group Takaka Terrane rocks in south-central Fiordland, and undifferentiated Deep Cove Gneiss high-grade metasedimentary rocks of western Fiordland—are all stitched by c. 355–348 Ma old plutons, indicating they have been in close proximity since at least c. 355–348 Ma. In south-central Fiordland, c. 355–348 Ma old plutons cut across fabrics defined by upper amphibolite facies mineral assemblages, indicating low pressure/high temperature metamorphism in this area before this time.\ud \ud The c. 164 Ma old leucocratic Lake Mike Granite is a unique pluton in southwest Fiordland with no obvious correlatives. Plutons emplaced between c. 140 and 125 Ma are similar to the Rahu Suite, although isotopic data are required to confirm this correlation. Rahu Suite plutonism may therefore have begun by c. 140 Ma, rather than c. 120 Ma as previously suggested. Plutons emplaced between c. 125 and 110 Ma have high Sr/Y ratios comparable with the Separation Point Suite. They occur in both an outboard location around Lake Poteriteri and an inboard location around the western end of Dusky Sound. The c. 115 Ma two-mica garnet granites of the Anchor Island Intrusives #2 probably formed by partial melting of adjacent ortho- and paragneisses, indicating that upper amphibolite facies metamorphism in western Dusky Sound occurred during the Early Cretaceous.\ud \ud The Dusky Fault does not pass directly out to the coast through outer Dusky Sound as previously mapped. Instead it merges with the major northeast-striking Lake Fraser Fault at Cascade Cove, which crosses the outer coast near West Cape. The Last Cove Fault is a minor structure which cannot be traced beyond Last Cove rather than a major fault of regional extent as has been previously suggested

The Tongon Au deposit, northern Côte d'Ivoire : an example of Paleoproterozoic Au skarn mineralization

The Tongon deposit in northern Côte d’Ivoire is the first reported occurrence of Au skarn mineralization hosted in Paleoproterozoic greenstone rocks of the West African craton. Tongon is an unusually large skarn (3.8 Moz at 2.5 g/t Au) replacing noncarbonate host rocks. The deposit is hosted exclusively in basaltic-andesitic crystal tuffs of the Senoufo greenstone belt. All other rock types in the local stratigraphy, including carbonaceous shales, siltstones, and dacitic crystal and lapilli tuffs, are devoid of mineralization. This observation implies a strong bulk compositional control on the distribution of the skarn. At the district scale, the Tongon hydrothermal system is confined to a corridor of ENE-striking orogen-oblique transfer faults, which link orogen-parallel N-to NNE-striking reverse faults to the north and south. Ferroan A-type granites and lamprophyric dikes also occur along these orogen-oblique faults. To date, no Au skarn mineralization has been discovered outside the corridor of ENE-striking faults elsewhere in the Senoufo belt. The alteration haloes surrounding the deposit formed during three main stages: stage 1, early/distal potassic (biotite-K-feldspar-actinolite) metasomatism; stage 2, prograde clinopyroxene ± grossularitic garnet skarn; and stage 3, retrograde skarn consisting of epidote-clinozoisite-prehnite-albite and slightly later quartz-sulfide-Au. Garnets contain high Al and Ti, and the skarns have elevated Ni and Cr, reflecting the mafic composition of the host rocks. Proximal to peripheral mineral zonation patterns are defined by decreases in the ratio of garnet to pyroxene, increasing Fe in pyroxene, higher Au concentrations, and an increase in the intensity of retrograde alteration, seen as a change from white-to green-colored skarn. Spatially, gold-rich stage 3 alteration coincides with stage 2 intermediate diopside-rich skarn and distal hedenbergite-ferroactinolite skarn, whereas the proximal garnet-bearing skarn typically has much lower Au grades. Fluid inclusions studies in the prograde skarn assemblages show primary, high temperature (>400°C), moderately saline (8–14 wt % NaCl equiv) H2O-NaCl-CaCl2 inclusions, with pressures estimated at 2 ± 0.5 kbar. The source of these fluids remains unclear, as plutonic rocks immediately to the west of Tongon intrude the skarn. U-Pb dating of hydrothermal titanite indicates the Au skarn formed between 2139 ± 21 and 2128 ± 21 Ma, 20 to 70 m.y. before the major episode of orogenic Au mineralization in southwest Ghana and western Mali. Dating provides further evidence that Au mineralization within the Paleoproterozoic rocks of West Africa craton occurred over several tens of millions of years through a variety of different processes

Tectonic model for development of the Byrd Glacier discontinuity and surrounding regions of the Transantarctic Mountains during Neoproterozoic-Early Paleozoic

The Byrd Glacier discontinuity us a major boundary crossing the Ross Orogen, with crystalline rocks to the north and primarily sedimentary rocks to the south. Most models for the tectonic development of the Ross Orogen in the central Transantarctic Mountains consits of two-dimensional transects across the belt, but do not adress the major longitudinal contrast at Byrd Glacier. This paper presents a tectonic model centering on the Byrd Glacier discontinuity. Rifting in the Neoproterozoic producede a crustal promontory in the craton margin to the north of Byrd Glacier. Oblique convergence of the terrane (Beardmore microcontinent) during the latest Neroproterozoic and Early Cambrian was accompanied by subduction along the craton margin of East Antarctica. New data presented herein in the support of this hypothesis are U-Pb dates of 545.7 ± 6.8 Ma and 531.0 ± 7.5 Ma on plutonic rocks from the Britannia Range, subduction stepped out, and Byrd Glacier. After docking of the terrane, subduction stepped out, and Byrd Group was deposited during the Atdabanian-Botomian across the inner margin of the terrane. Beginning in the upper Botomian, reactivation of the sutured boundaries of the terrane resulted in an outpouring of clastic sediment and folding and faulting of the Byrd Group

Geology and geochronology of the Archean plutonic rocks in the northeast Democratic Republic of Congo

Here we report the first regional-scale study of Archean plutonic rocks from 50,000 km of the northeast Democratic Republic of Congo (DRC). We include 50 new U-Pb zircon Sensitive High-Resolution Ion MicroProbe (SHRIMP) ages supported by petrographic and whole rock geochemical data from a further ~400 samples, and 39 additional U-Pb zircon ages reported by Kabete et al. (submitted) and Bird (2016). Felsic-intermediate magmatism across the northeast DRC occurred from ~ 3200 to 2530 Ma. Plutonism before ~ 2670 Ma is restricted to the West Nile Gneiss in eastern and northern-most DRC, whereas plutonism across the remainder of the northeast DRC initiated between 2670 and 2640 Ma. Two Neoproterozoic granite plutons ~ 1000–950 Ma are also present within the West Nile Gneiss. Magmatism between ~ 2670 and 2530 Ma marks the principal period of crustal growth in the northeast DRC. Felsic-intermediate plutonism between ~ 2670 and 2600 Ma included two suites of magnesian, calc-alkaline rocks, (1) a sodic-calcic suite with high Sr/Y ratios (>40) comparable with tonalite-trondhjemite-granodiorite (TTG) suites in other Archean terranes, and (2) a calc-alkaline to high-K suite of granitoids with low Sr/Y ratios ( 40 km is inferred to have produced the high Sr/Y magnesian granitoids, whereas the low Sr/Y magnesian granitoids were derived from melting-assimilation-storage-hybridization (MASH) processes in the overlying low-mid crust during the same period. Trans-lithospheric extension after ~ 2600 Ma, enabled asthenospheric mantle to interact with the base of the crust, resulting in high-temperature melting that produced the HFSE-elevated granitoids. Inherited Meso- and Paleoarchean zircons are almost completely restricted to the area within 30–40 km of the West Nile Gneiss, implying most of the northeast DRC is underlain by juvenile Neoarchean crust