Fenites associated with carbonatite complexes : a review

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Carbonatites and alkaline-silicate rocks are the most important sources of rare earth elements (REE) and niobium (Nb), both of which are metals imperative to technological advancement and associated with high risks of supply interruption. Cooling and crystallizing carbonatitic and alkaline melts expel multiple pulses of alkali-rich aqueous fluids which metasomatize the surrounding country rocks, forming fenites during a process called fenitization. These alkalis and volatiles are original constituents of the magma that are not recorded in the carbonatite rock, and therefore fenites should not be dismissed during the description of a carbonatite system. This paper reviews the existing literature, focusing on 17 worldwide carbonatite complexes whose attributes are used to discuss the main features and processes of fenitization. Although many attempts have been made in the literature to categorize and name fenites, it is recommended that the IUGS metamorphic nomenclature be used to describe predominant mineralogy and textures. Complexing anions greatly enhance the solubility of REE and Nb in these fenitizing fluids, mobilizing them into the surrounding country rock, and precipitating REE- and Nb-enriched micro-mineral assemblages. As such, fenites have significant potential to be used as an exploration tool to find mineralized intrusions in a similar way alteration patterns are used in other ore systems, such as porphyry copper deposits. Strong trends have been identified between the presence of more complex veining textures, mineralogy and brecciation in fenites with intermediate stage Nb-enriched and later stage REE enriched magmas. However, compiling this evidence has also highlighted large gaps in the literature relating to fenitization. These need to be addressed before fenite can be used as a comprehensive and effective exploration tool.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant No 689909

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

The age of the Sokli carbonatite, Finland, and some relationships of the North Atlantic alkaline igneous province

Nine dates from the Sokli area are presented, including four not previously published. Dates of the carbonatite range from 334 to 392 my. with one markedly discordant date of 247 my. Fenites give dates ranging from 354 ± 19 my, close to the carbonatite contact, to 488 ± 18 and 1 220 ± 40 my. at approximately one kilometre from the contact. Unfenitized basement granite and syenite are dated at 1 760 + 30 and 1 740 + 35 my. A summary is presented of the spatial and temporal relationships of the carbonatites and alkaline complexes of the North Atlantic alkaline igneous province as defined by Doig (1970), for which there are now available some 50 isotopic dates. These fall into three main groups which correspond closely in time with the peaks of the Caledonian — Appalachian, Grenville, and Hudsonian — Svecokarelian orogenic episodes. All three groups are represented in Canada and Europe, and two of them in Greenland. It is pointed out that in addition to the carbonatites, most of the world's described alkaline complexes which are layered occur within the province. The correspondence between the ages of emplacement of the igneous intrusions and the orogenic episodes is ascribed to deep tensional faulting in the forelands caused by down buckling of crustal plates along the orogenically active zones. The production of carbonatite magma and layered alkaline igneous complexes in this relatively narrow zone, and over a time span of 2 000 my. during which there was presumably differential motion between crustal plates and mantle, suggests that the lithosphere probably played an important role in the production of these exotic igneous rocks