We present new K-and L ′-band imaging observations for members of the young (3−5 Myr) σ Orionis cluster, obtained with UIST at UKIRT. We determine (K − L ′) colour excesses with respect to the photospheres, finding evidence for warm cir-cumstellar dust around 27 out of 83 cluster members that have masses between 0.04 M ⊙ and 1.0 M ⊙. This indicates a circumstellar disc frequency of at least (33...

The mid-Miocene (14.3 + 0.2 Ma; [1]) Ries impact crater located in southern Germany was formed in a two-layer target comprised of dominantly Mesozoic flat lying siliciclastic and carbonate sedimentary rocks that unconformably overlie crystalline Hercynian basement [2]. Ries is a complex crater with a total diameter of ~24 km [2]. Impactite and ejecta deposits are exceptionally well preserved. T...

Introduction: Kamacite grains corrode into tochilinite, an iron sulfide-hydroxide, if exposed to S-bearing water [1]. We evaluated this reaction in CM chondrites in order to determine the extent of aqueous alteration in these meteorites. Method: We looked at thin sections of Murchison, Cold Bokkeveld, Nogoya and Murray using optical microscopy and electron microprobe analysis (EMPA). We collect...

mercury mineralization has occurred in relation with a listwaenitic type hydrothermal alteration system in tavreh area located northwest of khoy. mercury-bearing alteration zone which has an area about 0.4 km2 is situated in one of aland river upstreams. the only mercury compound found in this district is mercury sulfide (cinnabar) deposited as vein and veinlet forms. geochemical investigations...

The northwestern part of the Kerman Cenozoic magmatic arc (KCMA) contains many areas with porphyry copper mineralization. In this research, we used the advanced space-borne thermal emission and reflection radiometer (ASTER) and Enhanced Thematic Mapper plus (ETM+) images of this region to map the distribution of hydrothermally altered rocks, based on their mineral assemblages. The spectral meas...

Alteration of fresh rock surfaces proceeds very rapidly in most terrestrial environments so that initial stages of modification of newly exposed surfaces are quickly masked by subsequent aqueous weathering processes. The hyper-arid and hypothermal environment of Beacon Valley, Antarctica, is limited in terms of available liquid water and energy available for alteration, which severely slows wea...