The pedogenesis of tin- and sulfide-lode mineralization at True Hill, southwestern New Brunswick

The subvolcanic True Hill granite porphyry in southwestern New Brunswick is genetically related to the Beech Hill series of granites of Devono-Carboniferous age. Three True Hill (TH) greisenised granite porphyry cupolas host Bi-Sn-Mo-W mineralized zones that have similarities to the nearby W-Mo-Bi orebodies at Mount Pleasant (MP). Tin-bearing lodes (0.03 to 0.66 wt, % Sn) are developed along faults and fractures that cut both mineralized (Bi-Sn-Mo-W) and unmineralized True Hill granite porphyry and enclosing metasedimentary rocks of the Waweig Formation. Within these lodes, particularly the central Main lode, two types of mineralization are present, an early chlorite-sulfide assemblage (Stage 1) and a later hematite-phengite-cassiterite assemblage (Stage 2) that replaces, in part, the earlier Stage 1 assemblage. The Stage 1 assemblage consists of Fe-rich septechlorite, pyrite, low-Fe sphalerite, magnetite, chalcopyrite, galena, Pb-Bi sulfides, tennantite, arsenopyrite and native Ag. Fe-Mg-Mn metasomatism responsible for chloritization was coincident with leaching of alkali and alkali-earth elements during feldspar hydrolysis. The Stage 1 assemblage (chl-sulfide) was formed at low temperature (<200°C) and low oxygen fugacity. The Stage 2 assemblage includes hematite, phengite, cassiterite and monazite with minor late quartz and fluorite. This assemblage was deposited at slightly higher temperatures (200"-300°CX higher oxygen fugacity (above hematite magnetite buffer) and at moderate pH 's (<musc-Kfs buffer). The overprinting of Stage 2 assemblages on portions of Stage 1 locally produces complex textures within the lodes at True Hill. The composition of both Stage 1 and 2 assemblages in the lodes is controlled by the (i) host rock composition and (ii) the mineralizing hydrothermal fluids. The deposition of Sn and LREE from Stage 2 fluids formed cassiterite and monazite along the reaction front between Stage 2 assemblages and chlorite-sulfide (Stage 1) and granite. Deposition of cassiterite probably occurred in response to (i) an increase in the Fe-Cl complexing at the expense of Sn- and LREE-C1 complexes during interation with Stage 1 assemblages, (ii) an increase in pH due to the feldspar hydrolysis in the granite and (iii) cooling of the fluid by the host rock. Although uneconomic, tin-sulfide lodes at True Hill have similarities with lodes developed within the North Zone of Mount Pleasant (New Brunswick) and Cornwall (England). However, the association of hematite and phengite with cassiterite mineralization is unique to this deposit RÉSUMÉ Le porphyre granitique subvolcanique de True Hill (Nouveau-Brunswick méridional) est lié par sa genèse au cortege granitique dévono-carbonifère de Beech Hill. Trois coupoles de porphyre granitique de True Hill (TH) altéré en greisen renferment des zones minéralisées en Bi-Sn-Mo-W et qui montrent des similitudes avec les gisements voisins de W-Mo-Bi présents a Mount Pleasant (MP). Des faisceaux filoniens porteurs d'étain (0,03 à 0,66% pds. Sn) s'installent le long de failles et de cassures recoupant les porphyres granitiques de True Hill, tant minéralises que stériles, ainsi que leur encaissant métasédimentaire (Formation de Waweig). Au sein de ces faisceaux, et surtout du faisceau central principal, on note deux types de minéralisation: un assemblage précoce à chlorite-sulfure (stage 1) et un assemblage tardif à hématite-phengite-cassitérite (stage 2) qui remplace en partie le premier. L'assemblage représentant le stage 1 consiste en de la septechlorite riche en Fe, de la pyrite, de la blende pauvre en Fe, de la magnétite, de la chalcopyrite, de la galène, des sulfures à Pb-Bi, de la tennantite, du mispickel et de l'argent natif. La métasomatose des Fe-Mg-Mn, dont provient la chloritisation, s'accompagne d'un lessivage des éléments alcalins et alcalino-terreux durant l’hydrolyse des feldspaths. L'assemblage denotant le stage 1 (chlorite-sulfures) se forma à basse température (<200°C) et faible fugacite d'oxygene. L'assemblage traduisant le stage 2 comporte de l'hématite, de la phengite, de la cassitérite, ainsi que de la monazite avec de faibles quantités de quartz et de fluorine tardifs. Cet assemblage fait inlervenir des températures un peu plus élevées (200°C a 300°C), une fugacité d'oxygène plus élevée (au-dessus du tampon hématite-magnétite) et des pH modérés (en-dessous du tampon des feldspaths potassiques de la muscovite). La surimpression des assemblages représentant le stage 2 sur des portions du stage 1 produit localement des textures complexes au sein des faisceaux filoniens de True Hill. La composition des assemblages dénotant tant le stage 1 que le stage 2 au sein de ces faisceaux est régie par: (i) la composition de l'encaissant et (ii) les étutdes minéralisateurs hydrothermaux. Le dépôt d'euin et de T.R. légères à paitir des fluides du stage 2 engendra de la cassitérite et de la monazite le long du front réactionnel, entre les assemblages témoins du stage 2, les chlorite-sulfures et le granite. Le dépôt de la cassitérite est probablement le fruit de: (i) une augmentation de la formation de complexes à Fe-Cl aux depens des complexes à Snet à Cl-T.R. légères durant l’interaction avec des assemblages du stage l,(ii)une élévation du pH par suite de 1 l’hydrolyse des feldspaths du granite, et (iii) le refroidissement du fluide par rencaissant Bien que de nature non économique, les faisceaux filoniens à étain et à sulfures présents à True Hill ne sont pas sans rappeler les faisceaux développés dans la Zone Nord de Mount Pleasant (Nouveau-Bnmswick) et à Cornwall (Angleterre). Cependant, ce gisement se singularise par l’association d'hématite et de phengite avec la minéralisation en cassitérite. [Traduit par le journal

The Ticks (Arachnida: Acari: Ixodida) of Arkansas

Although ticks are a nuisance to humans and other animals, they are an important part of the biota of North America. In addition, they are vectors of many tick-borne disease agents that can negatively affect higher vertebrates. In Arkansas, there have been no recent comprehensive summaries of the ticks (Acari: Ixodida) in the last 40+ yrs. Here, we provide a summary of the ticks of the state and note the disease agents they can transmit

Observing the Structure of the Landscape with the CMB Experiments

Assuming that inflation happened through a series of tunneling in the string theory landscape, it is argued that one can determine the structure of vacua using precise measurements of the scalar spectral index and tensor perturbations at large scales. It is shown that for a vacuum structure where the energy gap between the minima is constant, i.e. $\epsilon_i=i m_f^4$, one obtains the scalar spectral index, $n_s$, to be $\simeq 0.9687$, for the modes that exit the horizon 60 e-folds before the end of inflation. Alternatively, for a vacuum structure in which the energy gap increases linearly with the vacuum index, i.e. $\epsilon_i=\frac{i^2}{2} m_f^4$, $n_s$ turns out to be $\simeq 0.9614$. Both these two models are motivated within the string theory landscape using flux-compactification and their predictions for scalar spectral index are compatible with WMAP results. For both these two models, the results for the scalar spectral index turn out to be independent of $m_f$. Nonetheless, assuming that inflation started at Planckian energies and that there had been successful thermalization at each step, one can constrain $m_f<2.6069\times 10^{-5} m_P$ and $m_f<6.5396\times 10^{-7} m_P$ in these two models, respectively. Violation of the single-field consistency relation between the tensor and scalar spectra is another prediction of chain inflation models. This corresponds to having a smaller tensor/scalar ratio at large scales in comparison with the slow-roll counterparts. Similar to slow-roll inflation, it is argued that one can reconstruct the vacuum structure using the CMB experiments.Comment: v1: 8 pages, 2 figures; v2: grammatical typos corrected, results unchanged v3: To be published in JCA

Preliminary evidence of increased striatal dopamine in a nonhuman primate model of maternal immune activation.

Women exposed to a variety of viral and bacterial infections during pregnancy have an increased risk of giving birth to a child with autism, schizophrenia or other neurodevelopmental disorders. Preclinical maternal immune activation (MIA) models are powerful translational tools to investigate mechanisms underlying epidemiological links between infection during pregnancy and offspring neurodevelopmental disorders. Our previous studies documenting the emergence of aberrant behavior in rhesus monkey offspring born to MIA-treated dams extends the rodent MIA model into a species more closely related to humans. Here we present novel neuroimaging data from these animals to further explore the translational potential of the nonhuman primate MIA model. Nine male MIA-treated offspring and 4 controls from our original cohort underwent in vivo positron emission tomography (PET) scanning at approximately 3.5-years of age using [18F] fluoro-l-m-tyrosine (FMT) to measure presynaptic dopamine levels in the striatum, which are consistently elevated in individuals with schizophrenia. Analysis of [18F]FMT signal in the striatum of these nonhuman primates showed that MIA animals had significantly higher [18F]FMT index of influx compared to control animals. In spite of the modest sample size, this group difference reflects a large effect size (Cohen's d = 0.998). Nonhuman primates born to MIA-treated dams exhibited increased striatal dopamine in late adolescence-a hallmark molecular biomarker of schizophrenia. These results validate the MIA model in a species more closely related to humans and open up new avenues for understanding the neurodevelopmental biology of schizophrenia and other neurodevelopmental disorders associated with prenatal immune challenge