Pyroxenes from iron-rich igneous rocks in Rogaland, SW. Norway

An igneous complex, consisting of several anorthosite massifs and the layered intrusion(lopolith) of Bjerkreim-Sokndal, is surrounded by high-grade metamorphic sveconorwegian migmatites. The upper part of the lopolith or (quartz-)monzonitic phase(QfW) consists of iron-rich pyroxene monzonites and -syenites + fayalite + Fe-Ti oxides. It may be subdivided in a lower stage(l) characterised by primary orthopyroxene and an upper stage(2) characterised by (inverted/decomposed) pigeonite. Two massifs mainly consisting of similar rocks are concordantly intercalated in the migmatite terrane: the Botnavatnet and Gloppurdi Igneous Complexes(BIC and GIC). The BIC is mainly comparable with stage 2 of the QMP. Textural evidence and iron-enrichment in pyroxenes and olivines suggest that stage 1 of the QMP must be affixed to the leuconoritic phase of the layered lopolith. Pyroxene crystallization temperatures in the QMP and BIC are comparable: ca 1050- ca 900oC. The total pressure during pyroxene crystallization varied between 5-7 kb in the QMP and from 7-10 kb in the BIC. Isotopic ages are about 950 Ma and> 1060 respectively. During crystallization and subsequent cooling the water pressure was low. A great number of microprobe analyses of pyroxenes and olivines are presented. The low amount of 'non-quadrilateral components' makes these phases suitable for use as geobaro- and geothermometers. Textural data were obtained with a light-optical microscope and an electron microscope. Exsolution of pyroxenes proceeded by heterogeneous nucleation and growth. Texture and scale appear to be largely diffusion controlled. In clinopyroxenes cation diffusion is easier in the c- than in the adirection. Clinopyroxene is capable of stabilising thin pigeonite lamellae //"(001)" to below its transition temperature. Lamellae which exceed the critical lamellar thickness invert to the Rogaland inverted pigeonite lamellae.Anhydrous conditions during crystallization and cooling hampered the nucleation of orthopyroxene, which provided the conditions for the pigeonite-orthopyroxene transition to take place as a massive transformation. The transition did not take place by inversion but rather by decomposition

Introducing a new stratospheric dust-collecting system with potential use for upper atmospheric microbiology investigations

The stratosphere is a known host to terrestrial microbes of most major biological lineages, but it is also host to incoming meteoric dust. Our goal is to (1) introduce DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval), an active collector for the nondestructive collection of nano- to micrometer particles in the stratosphere between 30 and 40 km altitude, and (2) demonstrate that even a single particle can be collected free of resident atmospheric and laboratory contaminant particles. DUSTER improves the pervasive and persistent contamination problem in the field of aerobiology research. Here, we demonstrate the collector's advances by the identification of a (terrestrial) spore particle found among a population of nanometer-scale inorganic meteoric particles. This was possible because the size, shape, morphology, and chemical composition of each particle can be determined while still on the collector surface. Particles can be removed from DUSTER for specific laboratory analyses. So far, DUSTER has not been fitted for aerobiological purposes; that is, no attempts were made to sterilize the collector other than with isopropyl alcohol. Its design and laboratory protocols, however, allow adjustments to dedicated aerobiological sampling opportunities. Key Words: Aerobiology—Upper stratosphere—Dust collector—Single particles—Sampling. Astrobiology 14, 694–705

Laboratory analyses of meteoric debris in the upper stratosphere from settling bolide dust clouds

Bolide and fireball fragmentation produce vast amounts of dust that will slowly fall through the stratosphere. DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval) was designed to intercept the nanometer to micrometer meteoric dust from these events for laboratory analyses while it is still in the upper stratosphere. This effort required extraordinary precautions to avoid particle contamination during collection and in the laboratory. Here we report dust from the upper stratosphere that was collected during two campaigns one in 2008 and another in 2011. We collected and characterized forty five uncontaminated meteoric dust particles. The collected particles are alumina, aluminosilica, plagioclase, fassaite, silica, CaCO3, CaO, extreme F-rich COCa particles, and oxocarbon particles. These particles are found in friable CI and CM carbonaceous chondrite, and unequilibrated ordinary chondrite meteoroids that are the most common source of bolides and fireballs. The oxocarbons have no meteorite counterparts. Some F-bearing CaCO3 particles changed shape when they interacted with the ambient laboratory atmosphere which might indicate their highly unequilibrated state as a result of fragmentation. Equilibrium considerations constrain the thermal regime experienced by the collected particles between ∼2000°C and ∼1000°C, as high as 3700°C and as low as ∼650°C after 9s, followed by rapid quenching (μs) to below 1600°C, but equilibrium conditions during these events is most unlikely. So far the observed thermal conditions in these events put the temperatures between ∼4300°C and ∼430°C for 5s and high cooling rates. Such conditions are present in the immediate wake of meteors and fireballs

Introducing a New Stratospheric Dust-Collecting System with Potential Use for Upper Atmospheric Microbiology Investigations

The stratosphere is a known host to terrestrial microbes of most major biological lineages, but it is also host to incoming meteoric dust. Our goal is to (1) introduce DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval), an active collector for the nondestructive collection of nano- to micrometer particles in the stratosphere between 30 and 40 km altitude, and (2) demonstrate that even a single particle can be collected free of resident atmospheric and laboratory contaminant particles. DUSTER improves the pervasive and persistent contamination problem in the field of aerobiology research. Here, we demonstrate the collector's advances by the identification of a (terrestrial) spore particle found among a population of nanometer-scale inorganic meteoric particles. This was possible because the size, shape, morphology, and chemical composition of each particle can be determined while still on the collector surface. Particles can be removed from DUSTER for specific laboratory analyses. So far, DUSTER has not been fitted for aerobiological purposes; that is, no attempts were made to sterilize the collector other than with isopropyl alcohol. Its design and laboratory protocols, however, allow adjustments to dedicated aerobiological sampling opportunities. Key Words: Aerobiology—Upper stratosphere—Dust collector—Single particles—Sampling. Astrobiology 14, 694–705