PGE distribution in massive sulfide deposits of the Iberian Pyrite Belt

We present the first platinum group elements (PGE) data on seven massive sulfide deposits in the Iberian Pyrite Belt (IPB), one of the world largest massive sulfide provinces. Some of these deposits can contain significant PGE values. The highest PGE values were identified in the Cu-rich stockwork ores of the Aguas Teñidas Este (Σ PGE 350 ppb) and the Neves Corvo (Σ PGE 203 ppb) deposits. Chondrite normalized PGE patterns and Pd/Pt and Pd/Ir ratios in the IPB massive, and stockwork ores are consistent with the leaching of the PGE from the underlying rock sequence.     

Paleoenvironmental proxy records from Lake Hovsgol, Mongolia, and a synthesis of Holocene climate change in the Lake Baikal watershed

Here we discuss paleoenvironmental evolution in the Baikal region during the Holocene using new records of aquatic (diatom) and terrestrial vegetation changes from Hovsgol, Mongolia's largest and deepest lake. We reconcile previous contradictory Baikal timescales by constraining reservoir corrections of AMS dates on bulk sedimentary organic carbon. Synthesis of the Holocene records in the Baikal watershed reveals a northward progression in landscape/vegetation changes and an anti-phase behavior of diatom and biogenic silica proxies in neighboring rift lakes. In Lake Baikal, these proxies appear to be responsive to annual temperature increases after 6 ka, whereas in Lake Hovsgol they respond to higher precipitation/runoff from 11 to 7 ka. Unlike around Lake Baikal, warmer summers between 6 and 3.5 ka resulted in the decline, not expansion, of forest vegetation around Lake Hovsgol, apparently as a result of higher soil temperatures and lower moisture availability. The regional climatic proxy data are consistent with a series of 500-yr time slice Holocene GCM simulations for continental Eurasia. Our results allow reevaluation of the concepts of ‘the Holocene optimum’ and a ‘maximum of the Asian summer monsoon’, as applied to paleoclimate records from continental Asia.     

Far-Ultraviolet Stellar Emission Measurements from UVSTAR

We present the relevant results from three UVSTAR missions on STS69,STS85 and STS95. In particular we discuss three hot sub-dwarf star and CMa (500–1250 Å) observations.     

Palaeogeographic and geodynamic evolution of the Gondwana continental margins during the Cambrian

During the Cambrian, two types of continental margins occurred around Gondwana. The eastern margin (Antarctica, Australia and southern South America) was characterized by a narrow continental shelf with a steep slope separating the shallow water environment from a deep-oceanic one accompanied by mafidultramafic volcanics. The western margin was characterized by a wider continental shelf, probably passing gradually to an unknown outer basin. This comprised three main domains: the Asiatic shelf, composed of distinct cratonic blocks, presumably separated from each other by deeper-water/ volcanic intracontinental basins; the European shelf, characterized by the development of shallow intracontinental siliciclastic basins; and the Americanc-African shelf, morphologically and depositionally uniform. The distinction of these two Gondwana continental margins expresses their different geodynamic behaviour during Cambrian extensional tectonics. In fact, the sedimentary/palaeogeographic evolution, suggests the establishment of an active Pacific-like margin in the eastern domain, and the tentative establishment of a divergent Atlantic-like margin, in the westem one.     

Ureilitic breccias: clues to the petrologic structure and impact disruption of the ureilite parent asteroid

The majority of the 143 ureilite meteorites are monomict (unbrecciated) ultramafic rocks, which represent the mantle (olivine+low-Ca pyroxene residues and less abundant cumulates) of a partially melted (25–30%), carbon-rich asteroid 125 km in radius. Accumulated petrologic and geochemical studies of these meteorites have led to a picture of a ureilite parent body (UPB) that was stratified in mg#, pyroxene abundance and pyroxene type, due to the pressure dependence of carbon redox control, and which preserved a pre-magmatic heterogeneity in Δ¹⁷O. The absence, however, of ureilitic crustal rocks (i.e. basalts) in the meteorite record, leads to significant gaps in our knowledge of the geologic history of the UPB.

Ureilitic breccias provide considerable information that cannot be obtained from the monomict samples, and help to fill in those gaps. Fourteen ureilites are polymict breccias (at least three of which contain solar wind gases) that formed in a regolith. They contain a variety of clast types representing indigenous ureilitic lithologies not known among the monomict samples, as well as several types of non-indigenous impactor materials. In addition, one ureilite (FRO 93008) is a dimict breccia, consisting of two ultramafic lithologies that could not have formed in close proximity on the UPB.

Several feldspathic lithologies representing melts complementary to the monomict ureilite residues or cumulates have been recognized in polymict ureilites. From these lithologies we infer that melt extraction on the UPB was a rapid, fractional process in which trace element and oxygen isotopic equilibrium was not achieved. The majority of melts that reached the surface erupted explosively (due to high contents of CO/CO₂) and were lost into space. Thus, it is likely that the UPB never had an extensive basaltic crust. Melts generated at the shallowest depths and late fractionates, in which carbon had largely been consumed by reduction, were the most likely to have been preserved. Our sample of the UPB is limited to depths equivalent to 100 bars pressure or less, but minor augite-bearing feldspathic lithologies and related cumulates may represent melts derived from deeper.

In addition, we infer that the UPB was catastrophically disrupted, while still hot, by an impacting projectile. Meter-sized ejecta from this impact reaccreted into one or more daughter bodies, on which the brecciated ureilites formed. Ureilite meteorites are derived from these offspring, rather than from the UPB. The remnant of the original UPB may consist largely of olivine plus augite, and thus not resemble the majority of ureilites.     

Power, politics and networks: shaping partnerships for sustainable communities

The emergence of environmental governance for sustainable development as a field of inquiry has stimulated a plethora of research into new formations for governing the environment. Partnerships hold an exalted status in these formations, but there has been surprisingly little evaluative work of their activities. This paper extends that embryonic analysis through empirical consideration of a partnership established to foster the development of sustainable communities, specifically by stimulating greater public participation in positive environmental activities. Theoretical insights about patterns of power, perceived authority and legitimacy in the partnership are developed through a consideration of 'actor–spaces' and the 'sociology of translation' that emerge from actor–network theory.