Spectral reflectance properties of zeolites and remote sensing implications

The 0.3- to 26-μm reflectance spectra of a suite of 28 zeolites were measured and analyzed to derive spectral-compositional-structural relationships. Below ~7 μm, the spectra are largely dominated by absorption features associated with zeolitic water. At longer wavelengths, the spectra are dominated by absorption features associated with the aluminosilicate framework. The spectra exhibit a number of systematic variations which can be used for both structurl and compositional determinations. These include: (1) distinguishing different structural groups on the basis of wavelength position variations associated with absorption features in the 8.5- to 26-μm region that are related to differences in the structure of the aluminosilicate framework; (2) determining the major cation which is present (Ca, Na, K) and the associated electronic environment of the zeolitic water on the basis of how these cations hydrogen bond to the water molecules in the void spaces and consequently affect water-related absorption band positions, particularly in the 1.4, 1.9, and 2.0- to 2.5-μm regions; (3) determining the Al:(Al + Si) ratio and SCFM chemical index on the basis of absorption features in the 7- to 26-μm region which are most sensitive to these compositional variations; and (4) identifying ironbearing zeolites on the basis of absorption features in the 0.35- to 0.9-μm region. The wavelength position and number of H2O-associated absorption bands are sensitive to factors such as the type of major cation, degree of hydrogen bonding, and size of the void space, all of which are somewhat interrelated.This study was supported by a research grant from the Natural Sciences and Engineering Research Council of Canada, a contract from the Canadian Space Agency Space Science Program, a discretionary grant from the University of Winnipeg (to E.A.C.), and the Louise McBee Scholarship of the Georgia Association for Women in Education, University of Georgia (to P.M.A.).This study was supported by a research grant from the Natural Sciences and Engineering Research Council of Canada, a contract from the Canadian Space Agency Space Science Program, a discretionary grant from the University of Winnipeg (to E.A.C.), and the Louise McBee Scholarship of the Georgia Association for Women in Education, University of Georgia (to P.M.A.).https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2000JE00146

Application of quality assurance human factors and reliability principles to the prevention of major environment, safety, and health incidents

The study described in this report is part of a program to investigate how proven principles and techniques from the disciplines of quality assurance, reliability, and human factors might be used, or modified, to support environment, health, and safety programs. This report describes a study undertaken to determine whether there appears to be genuine, potential benefit from the use or modification of such principles or techniques in accident prevention. Results are based on a hindsight analysis of major accidents which have occurred

Paleoproterozoic Reworking of Archean Crust and Extreme Back‐Arc Metamorphism in the Enigmatic Southern Trans‐Hudson Orogen

Abstract The crustal evolution of the southernmost ∼2000–1800 Ma Trans‐Hudson orogen (THO) is enigmatic due to burial by Phanerozoic sediments. We provide new insights through petrochronologic analysis of a paragneiss drill core sample. Detrital zircon age peaks at 2625, 2340, and 1880 Ma and Hf isotopes suggest Paleoproterozoic arc development proximal to Archean source(s). Phase equilibria modeling and ternary feldspar thermometry suggest peak conditions of ≥1 GPa, ≥900°C, the first recognition of extreme, ultra‐high temperature metamorphism in the THO. The largely isobaric P‐T path, rapid heating rate, and ∼20 Myr duration (1872–1850 Ma) of peak conditions suggest that this metamorphism occurred in a back‐arc tectonic setting. The sample records post‐peak (1850–1815 Ma) mid‐crustal residence, slow cooling, and exhumation. Further retrogression occurred during Proterozoic regional exhumation (1630–1470 Ma) and Phanerozoic (360–220 Ma) reheating and/or fluid influx. Evidence for Paleoproterozoic arc(s) supports geophysical data for Archean cratonic and Paleoproterozoic arc crust in this region

Tin-Essako 001: A Metal-Rich Ureilite?

Metal-rich achondrites include a variety of types, and likely have a variety of origins. Models range from gravitational mixing at the core-mantle boundaries of differentatiated asteroids, to complex impact mixing scenarios. We describe a new type of metal-rich achondrite that might be the first metal-rich ureilite

The first main group ureilite with primary plagioclase: A missing link in the differentiation of the ureilite parent body

International audienceMS-MU-012, a 15.5 g clast from the Almahata Sitta polymict ureilite, is the first known plagioclase-bearing main group ureilite. It is a coarse-grained (up to 4 mm), equilibrated assemblage of 52% olivine (Fo 88), 13% orthopyroxene (Mg# 89.2, Wo 4.5), 11% augite (Mg# 90.2, Wo 37.3), and 14% plagioclase (An 68), plus minor metal and sulfide. The plagioclase grains have been secondarily remelted and internally recrystallized, but retain primary external morphologies. Melt inclusions occur in olivine. Rounded chadocrysts of olivine and orthopyroxene are enclosed in augite grains. In terms of texture, mineralogy, major and minor element mineral compositions, and oxygen isotopes, MS-MU-012 is virtually identical to the archetypal Hughes-type main group ureilites, with the significant addition of primary plagioclase. We conclude that MS-MU-012 formed as a cumulate in a common lithologic unit with the Hughes-type ureilites. Based on reconstructed compositions of melts trapped in olivine, orthopyroxene, and augite in the Hughes-type samples, we infer that the parent magma of the Hughes unit originated as a late melt in the incremental melting of the ureilite parent body (UPB), near the end of the melting sequence, but was not completely extracted from the mantle like earlier melts and was emplaced in an intrusive body. MELTS calculations indicate that olivine began to crystallize at ~1260 °C, followed shortly thereafter by co-crystallization of orthopyroxene and augite. Plagioclase began to crystallize at ~1170-1180 °C. Graphite was buoyant in the melt and became heterogeneously distributed in flotation cumulates. Residual silicate liquid was extracted from the cumulate pile and could have crystallized to form the "labradoritic melt lithology" (with plagioclase of An ~68-35), which is partially preserved as clasts in polymict ureilites. The final equilibration temperature recorded by the Hughes unit was ~1140-1170 °C, just before catastrophic disruption of the UPB. MS-MU-012 provides a critical missing link in the differentiation history of this asteroid

Replication Data for: The first main group ureilite with primary plagioclase: A missing link in the differentiation of the ureilite parent body

MS-MU-012, a 15.5 g clast from the Almahata Sitta polymict ureilite, is the first known plagioclase-bearing main group ureilite. It is a coarse-grained (up to 4 mm), equilibrated assemblage of 52% olivine (Fo 88), 13% orthopyroxene (Mg# 89.2, Wo 4.5), 11% augite (Mg# 90.2, Wo 37.3), and 14% plagioclase (An 68), plus minor metal and sulfide. The plagioclase grains have been secondarily remelted and internally recrystallized, but retain primary external morphologies. Melt inclusions occur in olivine. Rounded chadocrysts of olivine and orthopyroxene are enclosed in augite grains. In terms of texture, mineralogy, major and minor element mineral compositions, and oxygen isotopes, MS-MU-012 is virtually identical to the archetypal Hughes-type main group ureilites, with the significant addition of primary plagioclase. We conclude that MS-MU-012 formed as a cumulate in a common lithologic unit with the Hughes-type ureilites. Based on reconstructed compositions of melts trapped in olivine, orthopyroxene, and augite in the Hughes-type samples, we infer that the parent magma of the Hughes unit originated as a late melt in the incremental melting of the ureilite parent body (UPB), near the end of the melting sequence, but was not completely extracted from the mantle like earlier melts and was emplaced in an intrusive body. MELTS calculations indicate that olivine began to crystallize at ~1260 °C, followed shortly thereafter by co-crystallization of orthopyroxene and augite. Plagioclase began to crystallize at ~1170–1180 °C. Graphite was buoyant in the melt and became heterogeneously distributed in flotation cumulates. Residual silicate liquid was extracted from the cumulate pile and could have crystallized to form the “labradoritic melt lithology” (with plagioclase of An ~68-35), which is partially preserved as clasts in polymict ureilites. The final equilibration temperature recorded by the Hughes unit was ~1140–1170 °C, just before catastrophic disruption of the UPB. MS-MU-012 provides a critical missing link in the differentiation history of this asteroid

Improved confidence in (U-Th)/He thermochronology using the laser microprobe: An example from a Pleistocene leucogranite, Nanga Parbat, Pakistan

The newly developed laser microprobe (U-Th)/He thermochronometer permits, for the first time, the ability to generate precise (U-Th)/He cooling ages for even very young (<1 Ma) samples with a spatial resolution on the order of tens of micrometers. This makes it possible to test the reproducibility of independent (U-Th)/He age determinations within individual crystals, further increasing the reliability of the method. As an example, we apply it here to a Pleistocene granite from Nanga Parbat, Pakistan, where previous constraints on the thermal history are consistent with rapid exhumation and cooling. Twenty-one (U-Th)/He dates determined on two monazite crystals from a single granite sample yield a mean of 748,000 years with a ∼95% confidence level of ±19,000 years. There is no discernible variation in the distribution of (U-Th)/He ages in the cores of these crystals and therefore no evidence for the development of substantial diffusive-loss 4He zoning over 80% of the interior of the monazite crystals during postcrystallization cooling of the granite. Modeling of these data suggests that cooling at a mean rate of ∼300 K/Ma would be necessary to produce the observed ages and the lack of a 4He gradient, which is consistent with preexisting constraints for Nanga Parbat. Increased precision in thermochronology permits more tightly constrained exhumation models, which should aid geologic interpretation.National Science Foundation (U.S.