A Predictive Geospatial Exploration Model for Mississippi Valley Type Pb–Zn Mineralization in the Southeast Missouri Lead District

The Pb–Zn sulfide concentrations hosted by dolomitized Cambrian carbonates in Southeast Missouri are world-class Mississippi Valley Type (MVT) deposits. These deposits commonly are in sites where local Precambrian basement highs resulted in depositional pinchouts of the basal Cambrian sandstones that served as a regional aquifer for basinal fluid migration driven by late Paleozoic Ouachita deformation. Mineralization also appears to be spatially related to regional faults that probably served as local fluid conduits. Understanding spatial associations between sites of known mineralization and regional geology, geochemistry, and geophysics in Southeast Missouri will be a useful guide in future exploration efforts in this region and for similar geologic settings globally. The weights-of-evidence method is used to evaluate regional geology, geochemistry, and geophysical datasets and produce favorability maps for MVT deposits in Southeast Missouri. Host rock characteristics, regional structural controls, stream sediment geochemistry, and proximity to basement highs appear to be the most useful data for predicting the location of the major deposits. This work illustrates the potential utility of mineral potential modeling to prioritize areas for exploration and identify permissive areas for undiscovered MVT mineralization.

     

Experimental determination of activities in Fe−Mg olivine at 1400 K

The exchage equilibrium has been used to measure activity-composition relations along the olivine join FeSi_0.5O₂−MgSi_0.5O₂ at 1400 K and 1 atm pressure. Equilibrium Fe−Mg partitioning between the two phases was determined by reversing the compositions of olivine coexisting with oxide and matallic iron over the composition range Fo₂₃ to Fo₉₂. A detailed study of the thermodynamic properties of the oxide phase has recently been made by Srečec et al. and we have confirmed their results in the composition range of interest. Application of the oxide data to the exchange equilibrium enables the properties of olivine to be determined. Within experimental uncertainly (Fe, Mg)Si_0.5O₂ olivine can, at 1400 K, be treated as a symmetric solution with W _Fe-Mg ^o1 of 3.7±0.8 kJ/mol. The data permit the presence of only very slight asymmetry in the series. The data do not support recent assertions that olivine is highly non-ideal (W≈10 kJ/mol) under these conditions.     

Expériences sur la précipitation directe de l'apatite dans l'eau de mer: Implication dans la genèse des phosphorites

The direct precipitation of apatite in seawater is inhibited by Mg ions. The action of various factors on this precipitation is studied: addition of Ca, addition of F, reduction of pH and simultaneous effect of reduction of pH and addition either of F or of Ca. It is established that the reduction of the pH of seawater to 7 allows the precipitation of the apatite with a Ca/Mg ratio in the water of 1.2. The favourable environment for the settlement of natural apatite must then be either neutral or acid. This result is corroborated by the re-study of Gulbrandsen's equation. Such an acid environment with a high phosphorus content may be the result of oxidation of large quantities of organic matter due to previous intense biological activity. The acidity is probably brought about by bubbling of CO₂.     

Local variability in temperature, humidity and radiation in the BaekduDaegan Mountain protected area of Korea

A novel embedded sensor network records changes in key climatic-environmental variables over a range of altitude in the BaekduDaegan Mountain (BDM) of Gangwon Province in Korea, a protected mountain region with unique biodiversity undergoing climate change research. The investigated area is subdivided into three horizontal north-south study areas. Three variables, temperature (T, ℃), relative humidity (RH, %), and light intensity (LI, lumens m -2 , or lux, lx), have been continuously measured at hourly intervals from June, 2010 to September, 2011 using HOBO H8 devices at 10 fixed study sites. These hourly observations are aggregated to monthly, seasonal and annual mean values, and results are summarized to inaugurate a long-term climate change investigation. A region wide T difference in accordance with altitude, or lapse rate, over the interval is calculated as 0.4℃100 m -1 . T lapse rates change seasonally, with winter lapse rates being greater than those of summer. RH is elevated in summer compared to other seasons. LI within forestland is lower during summer and higher during other seasons. The obtained results could closely relate to the vegetation type and structure and the terrain state since data loggers were located in forestland.     

昆仑断裂带东段滑动速率梯度

欧亚大陆走滑断裂带是否实现对青藏地壳及岩石层的向东挤出,很大程度上取决于断层尾端变形的动力学机制。本文我们利用青藏高原北部昆仑断裂最东段千年尺度的地貌标志物提供一组最新的滑动速率测定结果。该断裂带是印度?亚欧碰撞带产生的最主要走滑断裂带之一,在西藏岩石层向东挤出的模型中扮演着主要的作用。曾有人争论在相当长的长度内该断裂显示出相同的滑动速率。黄河支流上的河流阶地位移以及阶地上物质的14C测年可以控制晚更新世至全新世断层以来的滑动速率。结果显示沿断裂东部约150km滑动速率从>10mm/a～<2mm/a自西向东系统地递减。这些数据向那些认为整条断裂滑动速率保持一致的观点提出质疑,相反揭示出位错的梯度性,这与那些在断层尾端预期的情形是类似的。另外,沿断层的滑动看起来在增厚的高原地壳内部终结,因此沿昆仑断裂的滑动导致的西藏岩石层的挤出都会被断裂尾端周围高原的内部变形所吸收。     

Review: Regional groundwater flow modeling in heavily irrigated basins of selected states in the western United States

Water resources in agriculture-dominated basins of the arid western United States are stressed due to long-term impacts from pumping. A review of 88 regional groundwater-flow modeling applications from seven intensively irrigated western states (Arizona, California, Colorado, Idaho, Kansas, Nebraska and Texas) was conducted to provide hydrogeologists, modelers, water managers, and decision makers insight about past modeling studies that will aid future model development. Groundwater models were classified into three types: resource evaluation models (39 %), which quantify water budgets and act as preliminary models intended to be updated later, or constitute re-calibrations of older models; management/planning models (55 %), used to explore and identify management plans based on the response of the groundwater system to water-development or climate scenarios, sometimes under water-use constraints; and water rights models (7 %), used to make water administration decisions based on model output and to quantify water shortages incurred by water users or climate changes. Results for 27 model characteristics are summarized by state and model type, and important comparisons and contrasts are highlighted. Consideration of modeling uncertainty and the management focus toward sustainability, adaptive management and resilience are discussed, and future modeling recommendations, in light of the reviewed models and other published works, are presented.     

The importance of social drivers in the resilient provision of ecosystem services

While a sustained flow of ecosystem services brings tangible benefits to humans, some ecosystem states and suites of services may be more desired by some people than others. Allocating or using the flow of services is loaded with asymmetries, complex power dynamics and political struggles between groups of people. We argue that the issues associated with such allocation and use questions are poorly integrated into the literatures of resilience, sustainability, and vulnerability. To illustrate this, we focus on three socially constructed factors that inhibit a fuller understanding about how to sustain the flow of ecosystem services: (1) rigidity/poverty traps; (2) power asymmetries; and (3) scientization of policy/politicization of science. These factors limit our ability to assess the sustainable flows of ecosystem services, and in particular to better understand the trade-offs and limits to aggregate human activity. We demonstrate that an improved understanding of the allocation trade-offs and limits to the flows of ecosystem services could result from more applied research that integrates the developing fields of deliberative democracy, pragmatic environmental philosophy, and legitimacy and rule compliance. Without the understanding that such integration would bring, researchers and policy makers risk underestimating the limits on flows of ecosystem services and how to accomplish their provision toward the greater collective - rather than individual - good.