0000000000393936
AUTHOR
R. Sacchi
Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield
Abstract Juvenile continental crust of the Arabian–Nubian Shield (ANS) formed within a Neoproterozoic supercontinent cycle. Subsequent late Neoproterozoic deposition overlapped a series of dramatic climatic events that are unparalleled in subsequent Phanerozoic time, as proposed by the “Snowball Earth” hypothesis. In particular, extreme negative δ 13 C excursions coincident with glacial diamictite and cap carbonate sequences imply that profound carbon flux changes accompanied widespread glacial transitions (Snowball Events). Such a succession appears to be partially preserved in metasediments of the diamictite-bearing Tambien Group of northern Ethiopia (Negash syncline). Here, a pronounced …
Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVusing soft electronb-tagging
The authors present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318 pb{sup -1} of data collected with the CDF II detector, they measure the t{bar t} production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9{sub -1.0}{sup +1.0}(stat.){sub -1.0}{sup +1.1}(syst.) pb. The cross section value assumes a top quark mass of m{sub t} is presented in the paper. This result is cons…
Kibaran magmatism and Pan-African granulite metamorphism in northern Mozambique: single zircon ages and regional implications
Abstract Single zircons from granitoid orthogneisses in the foreland of the Lurio Belt of northern' Mozambique were dated by the evaporation method and yielded 207 Pb/ 206 Pb magmatic emplacement ages between 1040.1 ±0.4 and 1148.2±0.4 Ma. These data confirm previous RbSr whole rock and SHRIMP zircon analyses and record a period of magmatic activity corresponding to the Kibaran event of east central Africa. A1300 Ma old zircon xenocryst in one sample suggests the presence of still older crust in the region. Metamorphic zircons from a granulite-facies psammopelitic gneiss of the Mugeba klippe, which is derived tectonically from the Lurio Belt, were dated by evaporation, conventional techniq…