Trace-element geochemistry and S–O isotopes in the fluorite-barite mineralization of Merguechoum,Moroccan eastern Meseta:insights into ore genesis to the Pangea rifting

The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of fluorite 2,and barite 2 with calcite and minor quartz and sulfides.The Merguechoum ore deposits have never been investigated.This study was the first contribution that studied the genesis of fluorite and barite.The ore occurs as dissemination within granite intrusion and also fills the NE-SWtrending meter-sized fractures and faults.The values of the total Rare Earth Elements and Yttrium(REY)and the ratios of LREY/HREY,Y/Ho,Tb/Ca,and Tb/La indicate that the Merguechoum fluorite precipitated from hydrothermal fluids,likely basinal brines,which interacted with the Hercynian granite.The REY data indicate that the ore-forming fluids of the early stage have intensely interacted with the Hercynian granite compared to those of the late ore stage.The gradual decrease in the europium(Eu/Eu^(*)),yttrium(Y/Y^(*)),and cerium(Ce/Ce^(*))anomalies and a low concentration ofΣREY observed in the second ore stage compared to the first ore stage suggest an increase in p H and fO_(2)and by inference a decrease in temperature during the evolution of the hydrothermal system.This evolution could be explained by fluid mixing between the ascending basinal hydrothermal fluids and the diluted sulfate-rich meteoric water barite separates from selected samples reveal that the dissolved sulfates(SO_(4)^(2-))were derived from Permian–Triassic sulfates and/or coeval poreseawater sulfates.The proposed fluid mixing triggered the precipitation of an early-stage F-Ba assemblage followed by the second-stage F-Ba mineralization.Geologic fieldwork,REY inventories,and isotope data point to the ore genesis during the Permian–Triassic extensional tectonic activity concerning the Pangea rifting.This extensional tectonic environment is likely the driving force that mobilized a large amount of the ore-forming basinal brines along the available faults and fractures to the loci of ore deposition.

Characterization of Organic Matter Preserved in the Triassic Lockatong Formation in the Newark Basin

This study is aimed at characterizing the organic matter preserved in the Triassic Lockatong formation deposited in the Newark Basin. On the basis of the TOC （Total Organic Carbon）, the Lockatong formation was deposited in a reducing environment in the deep NW part of the basin, which is favorable to the accumulation of organic matter. However, the Lockatong formation of the SE border of the basin was deposited in oxic conditions that prevented the preservation of organic matter if there is any. The structuration of the basin into deep subsiding NW section due to the reactivation of the NE-SW striking faults and the development of anoxic conditions were favorable for the accumulation and preservation of the organic matter in the deep part of the basin.

Relationship between Age and Neurogenesis in Old World Monkeys

Hippocampal neurogenesis continues throughout the lifespan of adult mammals, but the rates decline dramatically with increasing age. Among the factors that have been shown to affect neurogenesis, aging has been shown to be one of its most potent regulators in mice. The mechanism for the decline in neurogenesis with age is thought to be related to age-dependent changes in local and systemic neuroendocrinology and neurochemistry, as well as internal changes to precursor cells that result in decreased reactivity to normal stimuli. Since most of the data about neurogenesis and age were established from rodent studies, we sought to study this relationship in nonhuman primates in five previously studied cohorts of bonnet monkeys (Macaca radiata). In the present study, we statistically analyze the relationship of age and hippocampal neurogenesis rates, as measured by the number of DCX expressing cells in the subgranular zone of the dentate gyrus in 71 subjects with ages ranging from 3.5 to 17 years. We observed a non-significant relationship between age and doublecortin for subjects less than nine years old (corresponding to young and full adulthood) but a linear significant decline for subjects 9 years or greater (middle age and senescence). In contrast to previous studies that show neurogenesis to decline linearly throughout the lifespan, this study shows that neurogenesis occurs steadily throughout adulthood and begins to decline in middle age in bonnet macaques.

Interesting Features of Three-Dimensional Discrete Lotka-Volterra Dynamics

Discrete Lotka-Volterra systems in one dimension (the logistic equation) and two dimensions have been studied extensively, revealing a wealth of complex dynamical regimes. We show that three-dimensional discrete Lotka-Volterra dynamical systems exhibit all of the dynamics of the lower dimensional systems and a great deal more. In fact and in particular, there are dynamical features including analogs of flip bifurcations, Neimark-Sacker bifurcations and chaotic strange attracting sets that are essentially three-dimensional. Among these are new generalizations of Neimark-Sacker bifurcations and novel chaotic strange attractors with distinctive candy cane type shapes. Several of these dynamical are investigated in detail using both analytical and simulation techniques.