Evidence for meteorite impacts in the geological record may include the presence of shocked minerals, spherule layers, and geochemical anomalies. However, it is highly unusual to find unmelted crystals from the actual impactor within an ejecta layer. Here we detail the first recorded occurrence of vanadium-rich osbornite (TiVN) on Earth, from two sites on Skye, northwest Scotland, which are interpreted as part of a meteoritic ejecta layer. TiVN has only previously been reported as dust from comet Wild 2, but on Skye it has been identified as an unmelted phase. Both ejecta layer sites also contain niobium-rich osbornite (TiNbN), which has not previously been reported. An extraterrestrial origin for these deposits is strongly supported by the presence of reidite (a high-pressure zircon polymorph), which is only found naturally at sites of meteorite impact. Barringerite [(Fe,Ni) 2 P], baddeleyite (ZrO 2 ), alabandite (MnS), and carbon-bearing native iron spherules, together with planar deformation features and diaplectic glass in quartz, further support this thesis. We demonstrate through field relationships and Ar-Ar dating that the meteorite strike occurred during the mid-Paleocene. This is the first recorded mid-Paleocene impact event in the region and is coincident with the onset of magmatism in the British Palaeogene Igneous Province (BPIP). The Skye ejecta layer deposits provoke important questions regarding their lateral extent at the base of the BPIP and the possibility of their presence elsewhere beneath the much larger North Atlantic Igneous Province. BACKGROUNDMeteorite impact deposits are found throughout the geological record. However, in this paper we detail the youngest recorded UK meteorite impact event, located beneath mid-Paleocene lavas (Fig. 1A) at 2 sites 7 km apart on what is now the Isle of Skye, northwest Scotland (Fig. 1B). The only other known meteoritic ejecta deposit in Scotland is much older (1177 ± 5 Ma) than the Skye deposits and occurs within Precambrian rocks on the Scottish mainland (Parnell et al., 2011;Reddy et al., 2015).We present compelling mineralogical and textural evidence within the Skye deposits for impact-derived shock metamorphism at pressures ≥30 GPa. Within the deposits at both sites, unmelted vanadium-rich osbornite (TiVN) and niobium-rich osbornite (TiNbN) are preserved as part of the actual impactor. Recognition of actual unmelted impactor mineralogy has previously only been from the Chicxulub crater on the Yucatan Peninsula (Kyte, 1998).

Synopsis The occurrence of high-temperature calcic skarns is relatively rare, with around 30 being reported worldwide. Here, we report on a newly discovered occurrence of a melilite-bearing high-temperature calcic skarn at Camasunary Bay, Isle of Skye. The contact metamorphism was caused by the intrusion of the Cuillin Hills gabbro and the later intrusion of the Coire Uaigneich granophyre. The calcic skarn consists of a high-temperature assemblage of wollastonite, åkermanite–gehlenite, vesuvianite, tilleyite, spurrite. andradite–grossular garnet, monticellite and perovskite. It also includes the very rare Zr-rich garnet kimzeyite and baghdadite (Ca 3 (Zr,Ti)Si 2 O 9 ), indicating transfer of Zr, Ti and other incompatible element-rich fluids derived from the hydrous Coire Uaigneich granophyre. The calcic skarn contains numerous cherty nodules and stringers, which bear a remarkable resemblance to the Cambrian–Ordovician dolostone exposures observed in other parts of Skye. suggesting that the protolith was originally an impure dolomite. The nature of the contact between the calcic skarn and surrounding Torridonian sedimentary rocks could not be directly observed, but elsewhere on Skye this contact is the Kishorn Thrust plane. This has implications for the simplified tectonic map accompanying the British Geological Survey map of Broadford (Sheet 71W), which now requires modification.

Synopsis Silicic pyroclastic deposits, attributed to two discrete volcanic phases, are reported from a basal sequence of the Paleogene Skye Lava Field, NW Scotland. Phase 1 comprises relict silicic fall deposits that have been subsequently altered to a bed of K-bentonite. These fall deposits pre-date a thick ( c . 70 m) sequence of basaltic plateau lavas and a later underlying tholeiitic sill. The K-bentonite bed has a fabric that strongly resembles that of eutaxitic welded ignimbrite. Phase 2 comprises both basic and silicic ignimbrites that post-date the lowermost plateau lavas. The nature of these distinct ignimbrite lithofacies can be used to infer that eruption parameters, such as chemistry, intensity and flux output, underwent temporal variations. The recognition of these two phases of pyroclastic volcanism has major implications for the established sequence of the Skye Lava Field and gives important new insights into the nature of these Paleogene eruptions.

Caldera-forming eruptions are amongst the most hazardous events in the Earth’s history, and understanding their formation is essential to forecasting activity at active calderas worldwide.  In this study we present new field and geochronological evidence for a Paleocene-Eocene caldera from Skye, NW Scotland.  Magma exploited a regional thrust fault as a conduit, and then ponded against intrusive igneous rocks emplaced against a regional extensional fault.  Replenishment of silicic magma reservoirs with basaltic magma triggered eruptions.  The eruptions typically deposited extremely coarse ignimbrites, demonstrating catastrophic collapse of the caldera, which occurred via an inner ring fault and a complexly faulted marginal zone.  Collapse was followed by remobilisation of silicic magma and caldera resurgence.  The magma consumed dolostone country rocks, causing significant release of CO2 and contributed to the Paleocene-Eocene Thermal Maximum.  Our results demonstrate how tectonics localise magma and caldera development, and how this can cause cataclysmic volcanic and climatic hazards.