Variation of the Fe/Mn ratio of ferromanganese crusts from the Central North Pacific: implication for paleoclimate changes

Hydrogeneticferromanganesecrusts(Fe Mn crustshereafter),areinorganiccolloidprecipitatesfromseawater,whicharebelievedtohaverecorded theevolutionofelementalandisotopiccompositionsof seawaterovertime[1—7].Studiesontraceelements andisotopeshavebroughtmoreinsightsthanstudies onironandmanganesecontents.TheMn/Feratio hasbeenconsideredtoreflectwaterdepth,deep wa teroxygenation[8,9],andhasalsobeensuggestedasa reliablecriterionfordistinguishingdifferentgenetic typesofferromanganesedeposits[10].Apossi…     

Zircon U-Pb SHRIMP dating for the volcanic rocks of the Xiong’er Group: Constraints on the initial formation age of the cover of the North China Craton

The volcanic rocks of the Xiong’er Group occurringwidely in the southern part of the North China Craton,overlay the Archean and Paleo-Proterozoic crystallinebasement and are overlain by middle to late Paleozoicterrigenous detrital rocks, carbonate and tillite. TheXiong’er Group crops out over an area of more than60000 km2 in a thickness ranging from 3000 to 7000 m,the largest magmatism after the formation of the crystal-line basement of the North China Craton (Fig. 1(a)). TheXiong’er …