Granular 5-15nm diam (matrix) Spherulites l-2cm diam Blocky <300um diain (pumice) Mix 30% Cr + 70% KAF Cr, KAF Mix 15-50% Cr + 05-50% KAF, NaAF Cr, KAF Mix 30% Cr + 70S KAF Mix 40% Cr + 60% KAF Cr, KAF Mix 40% Cr, Q + 60S KAF to 20% Cr, q + 80% KAF Mix 50% Cr.Q + 50% KAF Mix 10% Cr.Q + 90% KAF Cr(Q), KAF Mix 30% Q + 70% KAr Q(Cr), KAF Lithic rich En echelon fractures parallel to fabric are filled with quartz En echelon fractures parallel to fabric are filled with quartz En echelon fractures parallel to fabric are filled with quartz Mix 40% Q, Cr + t >0% KAF Fractures are filled with quartz Q(Cr), KAF Mix 40% Q, Cr + 00% KAF Lithic rich (with Mix 20% q, Cr + 80% KAF cherts) q(Cr), KAF Fractures are filled with quartz

The Stac Fada Member of the Mesoproterozoic Stoer Group (Torridon Supergroup) in NW Scotland is a proximal ejecta blanket surrounding an unidentified asteroid impact crater. A combination of field observations of the ejecta deposit and underlying strata, the geographical distribution of terrane-identified basement clasts found embedded in the impactite, and anisotropy of magnetic susceptibility of the impact melt rocks at different locations, can constrain the crater location to be about 15-20 km WNW of Enard Bay and thus buried under Mesozoic sediments in The Minch. Syn-compressional structures within the suevite at Stattic Point give a clear indication of a south-easterly direction of mass motion. The signatures of two different terranes within the Lewisian gneiss help identify the origin of clasts found in the impactite at three locations. These clasts are un-shocked and interpreted as having been swept up by the density current post-impact; their geographic distribution provides an important clue to ejecta emplacement pathways crossing the Assynt and Gruinard terranes. Anisotropy of magnetic susceptibility is used to measure flow direction in pyroclastic density current deposits and is applied here to derive a direction of motion for the impactoclastic density current. It provides good agreement with the other independent methods.The Mesoproterozoic Stac Fada Member (SFM) of the Stoer Group of NW Scotland was first described as a basal conglomerate containing clasts of mafic dyke material (Peach et al., 1907). The abundant mafic material was subsequently recognized as comprising dark green, vesicular, devitrified glass fragments, and a volcaniclastic origin for the deposit was proposed: as an ash or pyroclastic flow (Lawson, 1972); as a volcanic peperite formed by a phreatomagmatic eruption of basic magma in contact with groundwater or shallow lakes (Sanders & Johnson, 1989); as an airfall tuff (Young, 1999(Young, , 2002, or; as volcanic mudflow (Stewart, 2002). However, Stewart (2002) also recognized that none of the proposed origins adequately explain all the observations. The identification of quartz grains with multiple sets of planar deformation features, platinum group elements in higher than normal crustal abundances and a non-terrestrial chromium isotope anomaly led to the re-interpretation of the Stac Fada Member as a proximal impact ejecta blanket beyond the margins of an as yet undiscovered meteorite impact crater (Amor et al., 2008). Consequently many of the depositional, petrographic, and geochemical features of this unit and adjacent strata took on a new significance. Although no source impact crater (or related crustal structure) has yet been identified on the Scottish mainland, the possibility remains that it has been obscured by thrust sheets of the Moine thrust belt (~430 Ma) that formed during the Caledonian Orogeny in the course of the closure of the Iapetus Ocean. Recently, Simms (2015) suggested that the

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No abstract

Thirty-eight hydrothermal minerals were identified from 356 drill-core specimens that were obtained from three Scientific Observation Holes (SOH-1, SOH-2, and SOH-4) drilled along the lower East Rift Zone (ERZ) of Kilauea Volcano, Hawaii. The minerals formed during alteration of basaltic rocks and glass by hot, circulating, waters in aquifers consisting of variable mixtures of meteoric water and sea water. Several zeolites, hydrated calcium silicates, carbonates, clays, silicates, sulfates, sulfides, and other minerals were found filling open spaces of vesicles, fractures, and between breccia fragments of the recovered drill core; many specimens that originally consisted of glass are completely altered to some of these minerals, especially clays. Several hydrothermal minerals (erionite, mordenite, truscottite, smectite, chlorite-smectite, chalcedony, anhydrite, and hematite), occur in the SOH drill holes at higher measured temperatures than the same minerals are found in geothermal drill holes of Iceland or other geothermal areas, suggesting that temperatures within the ERZ geothermal system have increased since the minerals formed. Fluid-inclusion freezing data for quartz, anhydrite, and calcite from the three SOH holes show that composition of the inclusion fluids ranges from dilute meteoric water to highly modified sea water concentrated by boiling. Comparison of measured drill-hole temperatures with fluid-inclusion homogenization-temperature data indicates that only about 15% of the fluid inclusions could have formed under the present thermal conditions. The majority of fluid inclusions studied apparently formed during one or more temperature fluctuations associated with the emplacement of nearby dikes and their subsequent cooling. Bacteria-like particles at 1734.6 m depth in SOH-4 could be very significant because the particles occurred at much hotter temperatures (about 265°C) than the generally accepted 110°C limit for survival of bacteria. The presence of Cl in the particles suggests that they might have lived in a saline environment and did not result from contamination by the fresh water drilling fluids. We reccomend that future drilling and subsequent handling of drill hole specimens in the ERZ and elsewhere employ controls to minimize and(or) recognize bacterial contamination.