TY  - JOUR
A1  - Schneider, K. P.
A1  - Hoffmann, J. E.
A1  - Münker, C.
A1  - Patyniak, Magda
A1  - Sprung, P.
A1  - Roerdink, D.
A1  - Garbe-Schönberg, D.
A1  - Kröner, A.
T1  - Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)
JF  - Chemical geology : official journal of the European Association for Geochemistry
N2  - A well-preserved sequence, by Archean standards, of mantle-derived metabasalts and metakomatiites forms large parts of the lower Onverwacht Group of the Barberton Greenstone Belt (South Africa). To elucidate the origin of mafic and ultramafic rocks from this 3.55 to 3.45 Ga sequence, we present a comprehensive geochemical dataset including major and trace elements as well as Lu-Hf and Sm-Nd isotope compositions for a variety of metavolcanic rocks. These include metabasalts of the amphibolite-facies Sandspruit and Theespruit Formations as well as metabasalts and metakomatiites of the lower greenschist-facies Komati Formation. Based on their incompatible trace element patterns, the basalts of the Sandspruit and Theespruit Formations can be subdivided into a light rare earth element (LREE) depleted group, a LREE-undepleted group, and a LREE-enriched group. Positive epsilon Hf-(t) and epsilon Nd-(t) values of ca. +3 to +4 and 0 to +2, respectively, together with depletions in Th and La-CN/Yb-CN indicate derivation of the LREE-depleted basalts from a depleted mantle source. However, chondritic epsilon Hf-(t) and epsilon Nd-(t) values combined with positive Th and La-CN/Yb-CN of the LREE-enriched samples indicate a contribution from older granitoid crust in the petrogenesis of these samples. Trace element patterns of komatiites and basalts of the Komati Formation are generally flat relative to primitive mantle with slight depletions in heavy rare earth elements and Th and overall positive epsilon Hf-(t) of + 2.5 +/- 3.5 (2 s.d.) and epsilon Nd-(t) of + 0.5 +/- 2.2 (2 s. d.). The coherence in trace element characteristics suggests a common magmatic origin for basalts and komatiites. This study reveals that the two lavas were derived from the same mantle plume, i. e. komatiites were formed by high degrees of melting of a depleted mantle source containing residual garnet and the basalts were formed by moderate degrees of partial melting in shallower regions of the mantle. Based on the current dataset, combined with published data, we propose a geodynamic model for the oldest units of the Barberton Greenstone Belt that describes the development from a submerged continental setting (for the Sandspruit and Theespruit Formations) to a submarine plateau setting (for the Komati Formation) as a consequence of continental rifting.
KW  - Paleoarchean
KW  - Assimilation-fractional crystallization
KW  - Mantle source
KW  - Ancient Gneiss Complex
Y1  - 2019
U6  - https://doi.org/10.1016/j.chemgeo.2019.02.020
SN  - 0009-2541
SN  - 1872-6836
VL  - 511
SP  - 152
EP  - 177
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Sulyanova, Elena A.
A1  - Shabalin, Anatoly
A1  - Zozulya, Alexey V.
A1  - Meijer, Janne-Mieke
A1  - Dzhigaev, Dmitry
A1  - Gorobtsov, Oleg
A1  - Kurta, Ruslan P.
A1  - Lazarev, Sergey
A1  - Lorenz, Ulf
A1  - Singer, Andrej
A1  - Yefanov, Oleksandr
A1  - Zaluzhnyy, Ivan
A1  - Besedin, Ilya
A1  - Sprung, Michael
A1  - Petukhov, Andrei V.
A1  - Vartanyants, Ivan A.
T1  - Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis
JF  - Langmuir
N2  - In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of temperature. A quantitative study of colloidal crystal lattice distortions and mosaic spread as a function of temperature was carried out using Williamson-Hall plots based on mosaic block model. The temperature dependence of the diameter of polystyrene particles was obtained from the analysis of Bragg peaks, and the form factor contribution extracted from the diffraction patterns. Four stages of structural evolution in a colloidal crystal upon heating were identified. Based on this analysis, a model of the heating and melting process in the colloidal crystal film is suggested.
Y1  - 2015
U6  - https://doi.org/10.1021/la504652z
SN  - 0743-7463
VL  - 31
IS  - 19
SP  - 5274
EP  - 5283
PB  - American Chemical Society
CY  - Washington
ER  -