Geological Processes, Geochemistry

"The secular cooling of the mantle and of the continental lithosphere trigger an increase in the area of emerged land. The corollary increase in weathering and erosion processes has major consequences for the evolution of Earth's external envelopes.
We developed a physical model to evaluate the area of emerged land as a function of mantle temperature, continental area, and of the distribution of continental elevations. Our numerical results show that less than 15% of Earth's surface consisted of emerged land by the end of the Archaean. This is consistent with many geological and geochemical observations.
To estimate the secular cooling of the continental lithosphere, we combined thermo-mechanical models with field observations. Our results, constrained by geological data, suggest that the Moho temperature has decreased by ~ 200ºC over 2.7 Ga in the Pilbara Craton.
To evaluate the effect of continental growth on the evolution of the area of emerged land, we developed a model based on published thermal evolution models. Our results suggest that the area of emerged land was less than 5% of Earth's surface in the Archaean, and that it does not depend on crustal growth. This allows to reconcile the evolution of oceanic 87Sr/86Sr with early
crustal growth models.
Continents are enriched in phosphorus, which is essential to the biosphere. The emergence of the continents would thus have triggered an increase in the production of oxygen by photosynthetic micro-organisms, possibly contributing to the oxidation of the atmosphere 2.4 Ga ago."

Le refroidissement seculaire du manteau terrestre et de la lithosphere continentale se traduit par l'augmentation de la surface de terres emergees. L'augmentation corollaire des processus d'alteration et d'erosion des silicates a des consequences majeures pour les enveloppes externes.
Nous avons developpe un modele physique qui permet d'evaluer la surface de terres emergees en fonction de la temperature du manteau, de la surface totale de continents, et de la distribution des altitudes continentales. Nos resultats numeriques montrent qu'a la fin de l'Archeen, moinsde 15% de la surface terrestre etaient emergee, en accord avec nombre d'observations geologiques et geochimiques.
Pour estimer le refroidissement seculaire de la lithosphere continentale, nous avons combine des modeles thermo-mecaniques avec des observations de terrain. Nos resultats, contraints par des donnees geologiques, suggerent que la temperature au Moho a diminue de ~ 200ºC en 2,7 Ga dans le craton des Pilbaras.
Pour evaluer l'effet de la croissance continentale sur l'evolution de la surface de terres emergees, nous avons developpe un modele base sur un modele d'evolution thermique publie. Nos resultats suggerent que la surface emergee, de moins de 5% de la surface terrestre a l'Archeen, depend peu de la croissance continentale. Ceci permet de reconcilier l'evolution du 87Sr/86Sr oceanique avec une croissance continentale precoce.
Les continents sont enrichis en phosphate, element essentiel a la biosphere. Leur emergence aurait donc engendre une augmentation de la production d'oxygene par des micro-organismes photosynthetiques, contribuant ainsi a l'oxydation de l'atmosphere il y a 2,4 Ga.

This paper discusses the advance of the speleothem luminescence
research.  Potential,  resolution  and  limitations  of  high  resolution  luminescence  speleothem  proxy  records  of
Paleotemperature, Solar Insolation, Solar Luminosity, Glaciations, Sea Level advances, Past Precipitation, Plants
Populations, Paleosoils, Past Karst Denudation, Chemical Pollution, Cosmic Rays Flux variations, Cosmogenic
Isotopes production and Supernova Eruptions in the Past, Advances of Hydrothermal Waters, and Techtonic Uplift are
discussed. It is demonstrated that speleothems allow extremely high resolution (higher than in any other paleoclimatic
terrestrial archives) and long duration of records. Some speleothems can be used as natural climatic stations for
obtaining of quantitative proxy records of Quaternary climates with annual resolution.

The British-Irish Palaeogene Igneous Province (BIPIP) is part of the larger North Atlantic Igneous Province and includes the lava fields of Antrim, Mull, and Skye. The Tardree Rhyolite Complex (TRC) in Northern Ireland forms an important stratigraphic unit between the Lower and Upper Basalt Formations of the Antrim Lava Group (ALG). Previous zircon age determinations obtained from the TRC have been used as a standard in zircon fission track studies, but contradict several 40Ar/39Ar sanidine and U-Pb zircon results. We provide new 40Ar/39Ar sanidine and U-Pb CA-TIMS zircon ages which resolve this discrepancy. Two sanidine samples from the Sandy Braes vent and the columnar-jointed dome-forming rhyolites of Tardree Forest yield a weighted mean 40Ar/39Ar age of 61.13 ± 0.42 Ma (2σ, internal error). Ten U-Pb CA-TIMS zircon analyses were undertaken, eight of which employed the CA-TIMS approach on both multi-grain fractions and single grains. Six of the CA-TIMS data yield a disequilibrium-corrected weighted mean 206Pb-238U age of 61.32 ± 0.09 Ma (2σ). The consistency of the 40Ar/39Ar ages with the CA-TIMS U-Pb zircon age, points to a closed system of both K and Ar since eruption. We propose that the crystallization age of the TRC be taken as 61.32 ± 0.09 Ma and that the currently used age of the zircon fission track standard (58.4 ± 0.7 Ma) be changed accordingly. This also places the eruption of the TRC in magnetochron C26r, which is consistent with the reversed polarity magnetic remanence observed in the ALG, and supports the conclusion of Ganerød et al. (2010) that the Lower Basalt Formation is older than the Vaigat Formation in Western Greenland. No resolvable zircon inheritance has been detected by the TIMS analyses, consistent with the fact that the temporal and geographic extent of rhyolitic magmatism within this sector of the BIPIP was very limited, and hence was unlikely to provide inherited magmatic zircons from slightly older magmas (antecrysts). Potentially older zircon xenocrysts would be derived from the underlying Caledonian basement (> 400 Ma) or yet older rocks. These should be easily detectable if the Tardree zircon was to be employed as a U-Pb zircon standard. The paired 40Ar/39Ar and 206Pb-238U results from this study indicate an age of 28.393 ± 0.194 Ma for the widely used Fish Canyon sanidine standard and gives further support to the recent calibrations of Kuiper et al. (2008) and Renne et al. (2010).

When illuminated  by ultraviolet  light, many  calcite speleothems  (stalagmites, stalactites,
flowstones)  display luminescence caused  by the presence of organic  (humic) substances  oc-
cluded  in the calcite.  The amplitude of luminescence varies  in a banded  pattern  parallel  to
growth layering. Through  laC and thermal ionization  mass spectrometry  uranium-series  dat-
ing, we show that cyclical oscillations in the luminescence  have periodicities  ranging  from a few
days to t10t yr. A well-defined  annual  cycle  is present in many vadose-zone  speleothems  and
can be used to define  the chronolory of short-term events.  This cycle is pmbably  a response to
hydrological events in the recharge  to the cave. Longer term oscillations  are inferred  to be
controlled by clirnaten  through  its effect on organic  activity  in the overlying soil

The composite intrusions of Drumadoon and An Cumhann crop out on the SE coast of the Isle of Arran, Scotland and form part of the larger British and Irish Palaeogene Igneous Province, a subset of the North Atlantic Igneous Province. The intrusions (shallow-level dykes and sills) comprise a central quartz–feldspar-phyric rhyolite flanked by xenocryst-bearing basaltic andesite, with an intermediate zone of dark quartz–feldspar-phyric dacite. New geochemical data provide information on the evolution of the component magmas and their relationships with each other, as well as their interaction with the crust through which they travelled. During shallow-crustal emplacement, the end-member magmas mixed. Isotopic evidence shows that both magmas were contaminated by the crust prior to mixing; the basaltic andesite magma preserves some evidence of contamination within the lower crust, whereas the rhyolite mainly records upper-crustal contamination. The Highland Boundary Fault divides Arran into two distinct terranes, the Neoproterozoic to Early Palaeozoic Grampian Terrane to the north and the Palaeozoic Midland Valley Terrane to the south. The Drumadoon Complex lies within the Midland Valley Terrane but its isotopic signatures indicate almost exclusive involvement of Grampian Terrane crust. Therefore, although the magmas originated at depth on the northern side of the Highland Boundary Fault, they have crossed this boundary during their evolution, probably just prior to emplacement.

Multiple competing hypotheses have been proposed to explain the source of loess dust in the Carpathian Basin yet none has been demonstrated. Here bulk and grain-size differentiated Nd and Sr isotopic and bulk and clay mineralogical compositions, together with detrital zircon ages and morphologies from loess along the Danube in the Carpathian Basin are used to demonstrate that no single method is capable of unequivocally isolating sources, yet combined, they allow for discriminating likely provenance. Zircon ages indicate multiple sources for Carpathian Basin loess, restricting the use of bulk or grain-size differentiation methods. Ambiguities are further highlighted by the fact that the Sr-Nd isotopic composition of Greenland dust is very similar to Carpathian loess. This match demonstrates that such methods are not always capable of unequivocally excluding unlikely potential source areas and implies that current hypotheses regarding the origin of Greenland dust require further evaluation. Sr isotopes are also limited by high dolomite contents of loess, while palygorskite is of questionable utility as a Saharan dust indicator due to its rapid weathering under typical Carpathian climates. In terms of specific Carpathian loess sources, alluvial fans of the Danube River likely contribute, but detrital zircon ages and morphologies suggest that a proportion directly originates from eroded uplands and local rocks throughout the basin, while detrital dolomite implies local, primary sources such as the Transdanubian Range. An upper limit of 5-10% is placed on the North African contribution to fine dust in loess of the mid-Carpathian Basin based on mineralogy and grain size. Overall, results suggest that the single grain (zircon) approach is likely the most diagnostic method to identify sources in loess studies, although to solve complex provenance issues, simultaneous consideration of the isotopic characteristics of more than one heavy (or light) mineral is required.

Mineral and aqueous geochemical data are combined with a conceptual groundwater flow model, to establish the origin and fate of iron, aluminium and manganese in the groundwater system of a small backbarrier island. The flow model domain consists of an unconfined island fresh groundwater lens overlying a semi-confined hypersaline aquifer. The two aquifers are separated by a discontinuous, clay-rich aquitard and both contain diffusion governed variable density flow fields. High concentrations of dissolved iron and manganese are associated with brackish to hypersaline groundwater, although there is no systematic relationship with salinity. Calculation of S2_/SO4 2_ and Fe2+/Fe3+ redox couples and the results of thermodynamic modelling show that redox disequilibrium in the groundwater is widespread. Groundwater samples containing aqueous sulphide and ferric iron complexes are supersaturated with respect to pyrite, goethite and haematite but the prevailing state of redox disequilibrium controls mineral dissolution and precipitation. Aqueous iron in the deeper regions of both aquifers is derived from the dissolution of iron oxide–hydroxides in lateritic palaeosols controlled by seasonal fluctuations in groundwater redox state. Aqueous manganese is potentially derived from the dissolution of ilmenite and amorphous oxide– hydroxides. The oxidation of iron sulphides contributes to the aqueous iron concentration and sulphuric acid production in the shallow groundwater. The solubility of aluminium is also limited by this process, governed by acidity regulation. A significant proportion of aqueous iron is transmitted from the semi-confined to the overlying unconfined aquifer through discontinuities in the aquitard layer. Movement of metals in solution outside the island groundwater system is restricted by the presence of diffusion boundaries within variable density transition zones.

The scope of activities of University Center for Space Research and Technologies (UCSRT) includes fundamental and applied research in the field of theoretical and experimental physics, space physics, geophysics, atmospheric physics, space, astrophysics, cosmology, space- materials science, development of mathematical models of processes in the near and distant space. At the Center, research and educational activities are performed in the field of space research and technologies, which have applications in electronics, telecommunications, geophysics, meteorology, ecology, archeology and other fields. The Center performs also research on properties of materials for space technologies.
Main educational activities of the Center are master's Program on “Space research” and Module 1 “Aerospace engineering” (small aero-spacecraft) of the master’s Program “Aerospace engineering and communications”, but its members lead also many courses of undergraduate programs in physics and engineering physics.
University Center for Space Research and Technologies is an independent research and educational unit of Sofia University "St. Kliment Ohridski", founded in 1987 and reorganized in 1992 into Unit of the Faculty of Physics. University Centre for Space Research and Technology has its own Rules of Operation, which is approved by decision of the Academic Council of Sofia University. According to the Council, UCSRT represents Sofia University and the Physics Faculty before the national and international bodies and organizations for Space Research.
UCSRT coordinates and manages the efforts of scientists from various departments of Sofia University and Bulgarian Academy of Sciences in temporary research teams, which accomplish scientific tasks related to Space Research and Technologies. Therefore, the Center has associated one internationally recognized observatory (IAU - А79), companies (such as O&K), active student workshop on astronomy, as well as individual professionals. The Center forms temporary laboratories on different scientific high-priority hot topics.
Applied research fields of the Centre include development of IR, UV and visible imaging systems and photometry for remote sensing observations from aircrafts, UAVs and satellites, research of Solar and Space Impacts on the Environment and applications of Space Research and Technologies in Archaeological research and prospecting. It includes also research and location of asteroids and dangerous Near- Earth Objects (NEO) and assessment of the damage which they can produce in result of potential collisions.
The Center has a highly qualified teaching staff, and its scientific production is published in journals, monographs and encyclopedias, some of which are issued by world-known academic publishers such as Elsevier and Thompson company issuing also ISI Citation index. Two of these monographs are awarded by an International Union of UNESCO Prize for the best publication in the relevant scientific field during the year.
The scientific outcome of the Center is significantly higher than the average production of the departments in the Faculty of Physics, despite its smaller staff: the results of the research activities of the members of the Center are published in 750 publications in scientific journals, monographs (mostly international), and conference proceedings, from which 560 publications in journals with impact factor.
Their results are presented in 167 reports at international congresses, conferences, symposia and schools, as 23 of them are invited or plenary talks.
They are cited worldwide 31290 times from foreign scientists, and research teams. 89 from the papers are cited more than 89 times, each (h-factor 89).
Specialists of the Center lead national and international research projects and programs. They have participated in one European, 10 international, 3 Italian and two Canadian research projects. At the moment they are leading two international research programs of one international scientific union. They review articles in prestigious international journals; are members of the editorial boards of international journals, editors of foreign monographs; evaluate Italian research projects in the fields of physics, astrophysics and Earth sciences; and participate in the appraisal of Italian universities. They chaired scientific organizing committees of five international scientific schools and conferences, and 6 sessions of other international conferences.
Specialists from UCSRT participate in large international collaborations and experiments in elementary particle physics, such as ATLAS, CHORUS, DELPHI, HARP, OPERA and H1.
The only Archaeo-geophysics laboratory in Bulgaria operates at the UCSRT.
The Center has intensive international collaborations with Universities and scientific institutions in Australia,  Austria,  Belgium,  Brazil,  Canada, China,  Croatia,  Czech  republic,  Egypt,  France,  Germany,  Hungary, India, Indonesia, Iran, Iraq, Italy, Luxembourg, Portugal, Puerto Rico, Romania, Russia, Slovenia, South Africa, Serbia, Spain, Swisszerland, UK, USA and other countries.

University Center for Space Research and Technologies has YouTube channel:
https://www.youtube.com/channel/UCyH3fFqMfKjLLI9jS4xnWHw

University Centre for Space Research and Technologies, Sofia University 
performs  scientific  and  applied  research,  and  education  in  Space  Research  and
Technologies, which have applications in Monitoring of Pollutions and Protection of the
Environment,  Prevention  of  Forest  Fires,  Global  Change,  GIS,  Electronics,
Telecommunications, Geophysics, Meteorology, Ecology, Archaeology and other fields.
It also performs research on properties of materials for space technology.
The  Centre  coordinates  and  manages  efforts  of  scientists  from  various  departments  of  Sofia
University and external institutions in temporary research teams, which accomplish scientific and
applied tasks related to Space Research and Technologies. Centre forms temporary laboratories on
different high- priority hot topics. It ensures higher flexibility than this of most scientific institutes
and university departments in the country. 
The  Centre  have  affiliated  companies  (O&K,  Hydroloc,  etc),  internationally  recognized
Astronomical  observatory  IAU-  79  and  active  Astronomical  student  circle,  which  also  performs
scientific research. 
Applied  research  fields  of  the  Centre  includes  development  of  IR,  UV  and  visible  imaging
systems and photometry for remote sensing observations from aircrafts, UAVs and satellites, Solar
and Space Impacts on the Environment and  applications of Space Research and Technologies in
Archaeological research and prospecting. 
Main  educational  activity  of  the  Center  are  master's  Programs  on  “Space  research”  and
“Aerospace engineering”. 
Center’s web page is: 
http://www.phys.uni-sofia.bg/eng/departments/ucsrt/index.html
Center’s YouTube channel is:
https://www.youtube.com/channel/UCyH3fFqMfKjLLI9jS4xnWHw
Center forms temporary laboratories, which work in its current directions of research, as its
laboratory in Archaeo-geophysics:
http://www.phys.uni-sofia.bg/bul/departments/ucsrt/agpl/index.html