Petrogenesis of the Late Eocene to Early Oligocene Yao'an Shoshonitic Complex,Southeastern Tibet:Partial Melting of an Ancient Continental Lithospheric Mantle beneath the Yangtze Block

Cenozoic potassic-ultrapotassic igneous rocks are widespread in the southeastern Tibetan Plateau.Their petrogenesis and magmatic processes remain subject to debate in spite of numerous publications.Almost all of the Cenozoic extrusive and intrusive rocks in the Yao’an area,western Yunnan Province,SW China,are geochemically shoshonitic,collectively termed here the Yao’an Shoshonitic Complex(YSC).The YSC is located in the(south)easternmost part of the ENE-WSW-trending,~550 km-long and~250 km-wide Cenozoic magmatic zone;the latter separates the orthogonal and oblique collision belts of the India-Eurasia collision orogen.Previously published geochronological and thermochronological data revealed that the rocks of the YSC were emplaced over a short timespan of 34-32 Ma.This and our new data suggest that the primary magma of the YSC likely was formed by partial melting of ancient continental lithospheric mantle beneath the Yangtze Block.This part of the continental lithospheric mantle had likely not been modified by any oceanic subduction.Fractionation crystallization of an Mg-and Ca-bearing mineral and TiFe oxides during the magmatic evolution probably account for the variable lithologies of the YSC.

New Taxa of Chrysomelidae (Insecta:Coleoptera) from Rovno Amber,Late Eocene

Leaf beetles Chrysomelidae of Rovno amber, from the Late Eocene, are recorded and described. Chrysomelidae of Rovno amber are represented by three subfamilies： Galerucinae （Alticini）, Chrysomelinae, and Enmolpinae. Two new genera and three new species of Alticini： Manobiomorpha Nadein, gen. nov. （type species Manobiomorpha eocenica Nadein, sp. nov.）, Psyllototus Nadein, gen. nov. （type species PsyUototus progenitor Nadein, sp. nov.）, and Crepidodera decolorata Nadein et Perkovsky, sp. nov. are described. A new chrysomeline genus and species Paleophaedon minutus Nadein gen. nov. et sp. nov. is described. Probable trophic association of Crepidodera decolorata sp. nov., the taxonomic positions of Manobiomorpha gen. nov. and PsyUototus gen. nov., and the composition of leaf beetle faunas of Middle and Late Eocene of Europe are discussed.

Lagoonal carbonate deposition preceding rifting-related uplift:evidence from the Bartonian-Priabonian(Eocene)of the northwestern Gulf of Suez(Egypt)

Sedimentary successions in the northwestern Gulf of Suez provide important clues to the understanding of the geological evolution of NE Africa during the middle and late Eocene.This study focuses on detailed facies analyses in order to characterize the depositional environments and system tracts of the Bartonian-Priabonian succession cropping out in this area.Bartonian-Priabonian carbonate deposits in five stratigraphic sections constitute,from base to top,the Gebel Hof,Observatory,Sannur,Qurn,and Wadi Hof Formations.These formations contain four local assemblage zones of larger benthic foraminifers.Analyses of litho-,bio-,and microfacies in the succession resulted in the recognition of 12 lithofacies types.These lithofacies are represented by packages of lime-mudstones,wackestones,packstones,pack-to grainstones,grainstones,rudstones,boundstones and dolomites.These lithofacies have been grouped into four geneticallyrelated facies associations that represent,respectively,tidal flats/shallow subtidal,restricted-shelf/lagoonal,shoal bar,and outer-shelf lagoon/reefal depositional environments in a downslope shallow-marine inner-ramp setting.The vertical transitions of these facies associations,representing facies changes through time,imply fluctuations of the regional sea level.The two peaks in the Bartonian correspond to well-known global eustatic sea-level rises;the pronounced Priabonian regression must be ascribed to the known global eustatic sea-level fall in combination with regional tectonic activity.The facies distribution suggests that the study area was located in the direct vicinity of some islands during the Bartonian-Priabonian.