scholarly journals Capability of U–Pb dating of zircons from Quaternary tephra: Jemez Mountains, NM, and La Sal Mountains, UT, USA

2018 ◽  
Vol 67 (1) ◽  
pp. 7-16 ◽  
Author(s):  
Jana Krautz ◽  
Mandy Hofmann ◽  
Andreas Gärtner ◽  
Ulf Linnemann ◽  
Arno Kleber
Keyword(s):  
Chemical Composition ◽  
Tephra Layer ◽  
Bulk Chemical Composition ◽  
Volcanic Material ◽  
Glass Shard ◽  
Three Samples ◽  
Jemez Mountains ◽  
Bulk Chemical ◽  
Age Range ◽  
Age Determinations

Abstract. Two Quaternary tephras derived from the Jemez Mountains, New Mexico – the Guaje and Tsankawi tephras – are difficult to distinguish due to their similar glass-shard chemical composition. Differences in bulk chemical composition are small as well. Here we examine the feasibility to assign an age to a distal tephra layer in the La Sal Mountains, Utah, by U–Pb dating of zircons and to correlate it with one of the two Jemez eruptions. We also dated original Jemez tephras for comparison. Even though the tephras are very young, we obtained reasonable age determinations using the youngest cluster of zircon grains overlapping in age at 2σ. Thereafter, the Guaje tephra is 1.513 ± 0.021 Myr old. The La Sal Mountains tephra is correlated with the Tsankawi tephra. Three samples yielded a common age range of 1.31–1.40 Myr. All ages are in slight disagreement with published age determinations obtained by 40Ar ∕ 39Ar dating. These findings indicate that distal Jemez tephras can be distinguished by U–Pb dating. Furthermore, we encourage giving this method a try for age assignments even of Quaternary volcanic material.

scholarly journals Synrift sandstones and clayey rocks: bulk chemical composition and location on a number of discriminant paleogeodynamic diagrams

2019 ◽  
pp. 439-465
Author(s):  
A. V. Maslov ◽  
V. N. Podkovyrov ◽  
E. Z. Gareev ◽  
A. D. Nozhkin
Keyword(s):  
Chemical Composition ◽  
Continental Margins ◽  
Bulk Chemical Composition ◽  
East European ◽  
Fine Grained ◽  
Sedimentary Deposits ◽  
Data Points ◽  
Bulk Chemical ◽  
Clayey Rocks ◽  
Active Continental Margins

The bulk chemical composition of synrift sandstones and associated clayey rocks has been analized, and the distribution of the fields they form has been studied on discriminant paleogeodynamic SiO2K2O/Na2O [Roser, Korsch, 1986] and DF1DF2 [Verma, Armstrong-Altrin, 2013] diagrams. The studied sandstones in terms of bulk chemical composition mainly correspond to greywacke, lititic, arkose and subarkose psammites; Sublitites and quartz arenites are also found. A significant part in the analyzed data massif consists of psammites, in which log(Na2O/K2O)-1.0; missing on the Pettijohn classification chart. This confirms our conclusion, based on the results of mineralogical and petrographic studies, that the sedimentary infill of rift structures unites immature sandstones, the detrital framework of which was formed due to erosion of local sources, represented by various magmatic and sedimentary formations. Synrift clayey rocks, compared with sandstones, are composed of more mature fine-grained siliciclastics. As follows from the distribution of figurative data points of clayey rocks on the F1F2 diagram [Roser, Korsch, 1988], its sources were mainly sedimentary deposits. The content of most of the main rock-forming oxides in the synrift sandstones is almost the same as in silt-sandstone rocks present in the Upper Precambrian-Phanerozoic sedimentary mega-complex of the East European Plate, but at the same time differs significantly from the Proterozoic and Phanerozoic cratonic sediments, as well as from the average composition upper continental crust. It is shown that the distribution of the fields of syntift sandstones and clayey rocks on the SiO2K2O/Na2O diagram does not have any distinct features, and their figurative data points are localized in the areas of terrigenous rocks of passive and active continental margins. On the DF1DF2 diagram, the fields of the studied psammites and clayey rocks are located in areas of riftogenous and collisional environments. We have proposed a different position of the border between these areas in the diagram, which will require further verification.

The preparation of silicate compositions by a gelling method

1968 ◽  
Vol 36 (282) ◽  
pp. 832-838 ◽  
Author(s):  
D. L. Hamilton ◽  
C. M. B. Henderson
Keyword(s):  
Chemical Composition ◽  
Chemical Analysis ◽  
Bulk Chemical Composition ◽  
Weight Yield ◽  
Bulk Chemical

SummaryA method for the preparation of chemically homogeneous powders by a weighing and gelling technique is described in detail. Stress is placed on the importance of the weight yield as an indication of the bulk chemical composition and on the chemical analysis of several portions to test the homogeneity. A list of recommended chemicals is included in an appendix.

scholarly journals A Particle-into-Liquid Collector for Rapid Measurement of Aerosol Bulk Chemical Composition

2001 ◽  
Vol 35 (3) ◽  
pp. 718-727 ◽  
Author(s):  
R. J. Weber ◽  
D. Orsini ◽  
Y. Daun ◽  
Y.-N. Lee ◽  
P. J. Klotz ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Bulk Chemical Composition ◽  
Rapid Measurement ◽  
Bulk Chemical

Alluvial Soil Chronosequence in the Inner Coastal Plain, Central Virginia

1993 ◽  
Vol 39 (2) ◽  
pp. 201-213 ◽  
Author(s):  
Jeffrey L. Howard ◽  
Dan F. Amos ◽  
W. Lee Daniels
Keyword(s):  
Chemical Composition ◽  
Soil Properties ◽  
Clay Mineral ◽  
Coastal Plain ◽  
Chemical Weathering ◽  
Bulk Composition ◽  
Alluvial Soil ◽  
Bulk Chemical Composition ◽  
Late Middle Miocene ◽  
Bulk Chemical

AbstractA chronological sequence of soils formed on a series of alluvial depositional surfaces ranging in age from late-middle Miocene to late Pleistocene was characterized to clarify soil-geomorphic relations and provide a basis for allostratigraphic subdivision of the inner Coastal Plain. On Quaternary river terraces, Ultic Hapludalfs containing abundant weatherable mineral species and clast types are estimated to have formed in 60,000-120,000 yr, whereas Typic Hapludults greatly depleted in weatherable minerals and showing strong weathering of clast types are estimated to be 700,000-1,600,000 yr old. Typic Paleudults with incipient plinthite, duripan, and ferricrete development characterize interfluves that have been little eroded since early Pliocene time (3.4-5.3 myr ago). Typic-Plinthic Paleudults with intense weathering of siliceous clasts and moderate to strong duripan and ferricrete development are found on surfaces that formed near the beginning of late Miocene time (10.8-13.0 myr ago). Chemical weathering in the chronosequence may be classified into three progressive stages: (1) decomposition of unstable sand- and silt-sized minerals into a mixed (stable + unstable) clay-mineral suite (stable Fe + Al/Si bulk chemical composition, < 106 yr); (2) transformation of mixed clay-mineral suite into a stable suite (increasing Fe + Al/Si bulk chemical composition, 106 - 107 yr); and (3) transformation of stable suite into ultrastable clay-mineral suite (increasing Fe/Si bulk composition, > 107 yr). Not all soil properties show unidirectional development, nor is a steady state of pedon development observed even after approximately 107 yr of chemical weathering. Soil development in the chronosequence is episodic. The transition from one phase to the next is marked by a change in rate, and sometimes a reversal in the direction, of development of one or more soil properties.

scholarly journals Geology and Geochemical Assessment of Maastrichtian Coal Quality in Abocho area, Northern Anambra Basin, Nigeria

2021 ◽  
pp. 1-15
Author(s):  
A. A. Zakari ◽  
B. S. Jatau
Keyword(s):  
Chemical Composition ◽  
Specific Gravity ◽  
Calorific Value ◽  
Average Density ◽  
Physical Analysis ◽  
Geochemical Analysis ◽  
Geologic Mapping ◽  
Bulk Chemical Composition ◽  
Anambra Basin ◽  
Bulk Chemical

Detailed geologic mapping and geochemical analysis of coal samples around Abocho area, northern Anambra Basin, Nigeria was conducted in order to assess the quality of the coals in the area. Proximate and ultimate analyses were carried out on coal samples from the Mamu Formation to determine its chemical characteristics.  Physical analysis was also carried out on the coal samples to determine the specific gravity, density and hardness. Geochemical analysis was also carried out on the associated rocks in the study area (Abocho), particularly Shales and Clays to determine their major oxides composition. The area is composed of the Maastrichtian Mamu Formation overlain by the Ajali Sandstone of the same age both dipping between 16°E and 19°E. The geologic mapping of Abocho area revealed two mappable lithologic units: The Mamu Formation and the Ajali Sandstone. The Proximate analyses indicates that the coal contains an average 7.15%, 35.53%, 36.24% of moisture content, volatile matter and fixed carbon respectively. These burns to generate 4,339 kcal/kg calorific value with 20.80% ash yield. The result of the ultimate analysis shows 57.81% organic carbon, 4.15% hydrogen, 8.41% oxygen, 1.39% nitrogen and 0.3% Sulphur. The physical analysis revealed that, the coal has an average specific gravity of 1.5g/cm, average density of 1.4g/cm3 and average hardness of 1.2. These characteristics qualify the coal to be ranked as high volatile sub-bituminous to marginal lignite. The coal is thus, suitable for combustion, gasification, electric power generation and industrial uses. Geochemical results show that the Shale contains 60% Silica (SiO2) and 26%Alumina (Al2O3) constituting 86% of bulk chemical composition. The Clay contains 70% Silica (SiO2) and 25% Alumina (Al2O3), constituting 95% of bulk chemical composition. The occurrences of CaO, NaO and K2O which are the major component of feldspar in clay suggests the clay to be of granitic origin possibly from Oban massif, east of the Anambra Basin. It also suggests low feldspar content.

scholarly journals The ore minerals of the Ilímaussaq intrusion: their mode of occurrence and their conditions of formation

1978 ◽  
Vol 127 ◽  
pp. 1-51
Author(s):  
S Karup-Møller
Keyword(s):  
Chemical Composition ◽  
Thermodynamic Data ◽  
Phase Correlation ◽  
Coarse Grained ◽  
Bulk Chemical Composition ◽  
Native Iron ◽  
Ore Minerals ◽  
Mode Of Occurrence ◽  
Bulk Chemical ◽  
Hydrothermal Veins

On the basis of their chemical composition, the Ilímaussaq ore minerals in pegmatites and hydrothermal veins have been subdivided into the following four associations: I Pb-Zn-Mo, II Cu-Sb (including two subtypes: IIA Cu-Sb and IIB Cu-Sb-S), III Fe-As and IV Fe-Ni-As-Sb. Accessory rock-forming ore minerals have been studied in heavy mineral concentrates isolated from the augite syenite and from the following agpaitic rocks: alkali granite, sodalite foyaite, naujaite, green lujavrite, medium- to coarse-grained lujavrite and black, red and white kakortokites. The ore minerals comprise sulphides (galena, sphalerite, molybdenite, pyrrhotite, troilite, marcasite, pyrite, chaIcopyrite and djerfisherite), native elements (tin, lead and iron), aIloys (seinäjokite [FeSb2] and unnamed Sn-Cu(-Pb)phase), arsenides (westerveldite and loeIlingite) and one antimonide (gudmundite). Oxides of iron, titanium and chromium have been identified. Native iron, native tin, unnamed Sn-Cu(-Pb)phase, decomposed wüstite and chromite may represent contaminated material. Some of the accessory rock forming ore minerals form two additional associations: V Fe-Cu and VI Fe-Ti-O. The accessory ore minerals in the agpaitic rocks crystallized relatively late compared to the silicate minerals. In the augite syenite the original pyrrhotite and associated chaIcopyrite crystallized from an immiscible sulphide phase. Correlation between accessory rock-forming ore minerals and bulk chemical composition of the major rocks is severely limited due to the lack of chemical data. The ore minerals in the rocks, pegmatites and veins crystallized at low sulphur and oxygen fugacities. The log αS2 and log fO2 ranges are semi-quantitatively estimated on the basis of published thermodynamic data.

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