SEARCH · Geology Reports

Results for “Chemistry International”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

173 records · Page 10Linked to original sources

USGS2017

Fluorine

Fluorine compounds are essential in numerous chemical and manufacturing processes. Fluorspar is the commercial name for fluorite (isometric CaF 2 ), which is the only fluorine mineral that is mined on a large scale. Fluorspar is used directly as a fluxing material and as an additive in different manufacturing processes. It is the source of fluorine in the production of hydrogen fluoride or hydrofluoric acid, which is used as the feedstock for numerous organic and inorganic chemical compounds. The United States was the world’s leading producer of fluorspar until the mid-1950s. In the mid-1970s, the U.S. fluorspar mining industry began to decline because of foreign competition. By 1982, there was essentially only a single U.S. producer left, and that company ceased mining in 1996. Consumption of fluorspar in the United States peaked in the early 1970s, which was also the peak period of U.S. steel production. Since then, U.S. fluorspar consumption has decreased substantially; the United States has nonetheless increased its imports of downstream fluorine compounds, such as, in order of tonnage imported, hydrofluoric acid, aluminum fluoride, and cryolite. This combination of no U.S. production (until recently) and high levels of consumption has made the United States the world’s leading fluorspar-importing country, in all its various forms. The number of fluorspar-exporting countries has decreased substantially in recent decades, and, as a result, the United States has become dependent on just a few countries to supply its needs. In 2013, the United States imported the majority of its fluorspar from three countries, which were, in descending order of the amount imported, Mexico, China, and South Africa. Geologically, in igneous systems, fluorine is one of a number of elements that are “incompatible.” These incompatible elements become concentrated in the residual magma while the common silicates crystallize upon magma ascent and cooling, leading to relatively high fluorine concentrations in the more evolved or differentiated igneous rocks and in hydrothermal deposits associated with those evolved igneous rocks. In sedimentary rocks, fluorine’s highest concentrations are found in phosphorites because fluorine substitutes for hydroxyl ions in apatite, which leads to fluorine concentrations of, typically, from 2 to 4 weight percent in phosphorites. Because of the presence of fluorine, phosphate fertilizer manufacturers can produce a fluorosilicic acid byproduct. Most deposits mined for fluorine are hydrothermal, however, and consist of fluorine minerals that precipitated from hot water. Magmatic brines and brines from deep within sedimentary basins that have high concentrations of dissolved fluoride are the mineralizing fluids for various types of hydrothermal fluorspar deposits. Relatively dilute hydrothermal fluids that formed in some volcanic rocks can also transport sufficient fluoride to form a high-grade fluorspar deposit. Fluorite has low solubility in a common range of hydrothermal temperatures, particularly from about 160 degrees Celsius (°C) down to 60 °C. The increasing fluorite solubility below 60 °C partly explains why some water with exceptionally high levels of dissolved fluorine are found even at ambient temperatures in evaporitic lake basins in some East African Rift valleys in Kenya and Tanzania. The geologic conditions that led to the high concentrations there are known to exist in a number of other places in the world as well, including, perhaps, places in the Basin and Range province of the United States. Eight minerals or mineral groups have sufficient fluorine in their structures to be considered as possible ores of the element; they are bastnaesite (also spelled bastnäsite; and other fluorocarbonates), cryolite, sellaite, villiaumite, fluorite, fluorapatite (in phosphorites), various phyllosilicates, and topaz. Fluorite is currently the only mineral that is mined for fluorine, and nomineral except fluorite is likely to become a source of commercially produced fluorine as a primary product as long as supplies from relatively thick and high-grade fluorite deposits continue to be available. At least seven classes (which include one subclass) of hydrothermal fluorite deposits are recognized; they are classified according to their tectonic and (or) magmatic settings, as follows: (1) carbonatite-related fluorspar deposits; (2) alkaline-intrusion-related fluorspar deposits; (3) alkaline-volcanic-related epithermal fluorspar deposits; (4) Mississippi Valley-type fluorspar deposits (and a subclass of salt-related carbonate-hosted fluorspar deposits); (5) fluorspar deposits related to strongly differentiated granites; (6) subalkaline-volcanic-related epithermal fluospar deposits; and (7) fluorspar deposits that appear to be conformable within tuffaceous limy lacustrine sediments. An eighth class (not hydrothermal) is that of fluorspar deposits concentrated in soils and weathered zones; that is, residual fluorspar deposits. Generally, fluorspar deposits related to strongly differentiated granites have larger tonnages and lower grades than carbonatite-related fluorspar deposits, which, in turn, have larger tonnages and lower grades than fluorspar vein deposits from various other classes. The United States has a few identified resources of fluorspar, most notably the Klondike II property in the Illinois- Kentucky fluorspar district located about 8 kilometers southwest of Salem, Kentucky, which has a large vein that contains at least 1.6 million metric tons at a grade of 60 percent CaF 2 (Feytis, 2009). Additional fluorspar resources of lower grade but larger tonnage have been identified at Hicks Dome in the Illinois-Kentucky fluorspar district and at Lost River near the western tip of the Seward Peninsula in Alaska, along with a couple of dozen smaller, higher grade resources. Internationally, new mines that either opened before the beginning of 2013 or were scheduled to open soon after that time include the Nui Phao tungsten-fluorspar-bismuth-copper-gold deposit in northern Vietnam; the St. Lawrence project in Newfoundland, Canada, which is located in a well-known fluorspar district; the Bamianshan deposit, which is related to a strongly differentiated granite in northwestern Zhejiang Province, China, near some of that Province’s large, subalkaline-volcanic-related epithermal veins; and the Nokeng project in South Africa, which is also related to a strongly differentiated granite. Other deposits in northwestern Australia, Nevada (United States), Norway, South Africa, and Sweden have been identified and could be put into production within just a few years. Among undiscovered resources, an interesting possibility might be to produce a fluorine product from evaporitic, high-fluorine, high-pH sodium-carbonate brines like Lake Magadi (Kenya) and Lake Natron (Tanzania) in Africa’s Eastern Rift Valley. In addition, apparently conformable fluorspar deposits in tuffaceous limy lacustrine sediments, such as those in Italy, are likely to occur in similar young alkalic volcanic settings elsewhere in the world. Modern geophysical and geochemical exploration techniques have typically not been brought to bear in exploration for new fluorspar deposits, although such techniques are likely to be used in future exploration. The tendency for fluorine to dissolve in significant concentrations in water at low temperature allows both surface water and groundwater to be used as sampling media in geochemical exploration. Evolved granite-related fluorspar deposits may be particularly susceptible to geophysical exploration methods because crystalline rocks that form a basement to sedimentary sections can be approximately defined with gravity and magnetic methods, and magnetite-bearing skarns can be directly detected with magnetic surveys. Environmental considerations of fluorine mining focus especially on drinking water, where high fluorine concentrations can lead to tooth decay; dental and skeletal fluorosis; and bone and cartilage conditions, including genu valgum, which is the crippling bone deformity more commonly known as knock knee. Trace amounts of other elements in fluorspar ores are a concern at some deposits; for example, high beryllium concentrations in alkaline-volcanic-related epithermal deposits or high cadmium concentrations associated with Mississippi Valley-type and salt-related carbonate-hosted fluorspar deposits. Future research might include testing whether fluorine can be extracted economically from high-pH, sodium-carbonate brines and exploring for new occurrences of apparently conformable fluorspar deposits in tuffaceous limy lacustrine sediments outside of the Latium Region of Italy. Other promising new areas of research could be studies of fluorspar deposit fluid inclusion compositions by quadrupole mass spectrometry, by noble gas mass spectrometry on irradiated fluid inclusions, or by chlorine isotopes, while also measuring the chemistry of the same fluid inclusions either by bulk crush-and-leach methods or by laser ablation-inductively coupled plasma mass spectrometry. Advanced studies of fluid inclusion chemistry could be applied beneficially to some of the enigmatic large epithermal fluorspar veins at various places in the world, where they might determine those deposits’ possible relationships to igneous intrusions, or to dissolved salt, or to heated meteoric water in volcanic sections, or perhaps to all three. This knowledge could help focus new exploration.

Professional Paper↗

USGS1993

An extremely low UPb source in the Moon: U Th Pb, Sm Nd, Rb Sr, and 40Ar 39Ar isotopic systematics and age of lunar meteorite Asuka 881757

We have undertaken U Th Pb, Sm Nd, Rb Sr, and 40 Ar 39 Ar "> 40 Ar 39 Ar isotopic studies on Asuka 881757, a coarse-grained basaltic lunar meteorite whose chemical composition is close to low-Ti and very low-Ti (VLT) mare basalts. The Pb Pb internal isochron obtained for acid leached residues of separated mineral fractions yields an age of 3940 ± 28 Ma, which is similar to the U-Pb (3850 ± 150 Ma) and Th-Pb (3820 ± 290 Ma) internal isochron ages. The Sm-Nd data for the mineral separates yield an internal isochron age of 3871 ± 57 Ma and an initial 143 Nd 144 Nd "> 143 Nd 144 Nd value of 0.50797 ± 10. The Rb-Sr data yield an internal isochron age of 3840 ± 32 Ma ( λ( 87 Rb) = 1.42 × 10 −11 yr −1 "> λ( 87 Rb) = 1.42 × 10 −11 yr −1 ) and a low initial 87 Sr 86 Sr "> 87 Sr 86 Sr ratio of 0.69910 ± 2. The 40 Ar 39 Ar "> 40 Ar 39 Ar age spectra for a glass fragment and a maskelynitized plagioclase are relatively flat and give a weighted mean plateau age of 3798 ± 12 Ma. We interpret these ages to indicate that the basalt crystallized from a melt 3.87 Ga ago (the Sm-Nd age) and an impact event disturbed the Rb-Sr system and completely reset the K-Ar system at 3.80 Ga. The slightly higher Pb-Pb age compared to the Sm-Nd age could be due to the secondary Pb (from terrestrial and/or lunar surface Pb contamination) that remained in the residues after acid leaching. Alternatively, the following interpretation is also possible; the meteorite crystallized at 3.94 Ga (the Pb-Pb age) and the Sm-Nd, Rb-Sr, and K-Ar systems were disturbed by an impact event at 3.80 Ga. The crystallization age obtained here is older than those reported for low-Ti basalts (3.2–3.5 Ga) and for VLT basalts (3.4 Ga), but similar to ages of some mare basalts, indicating that the basalt may have formed from a magma related to a basin-forming event (Imbrium?). The age span for VLT basalts from different sampling sites suggest that they were erupted over a wide area during an interval of at least ~500 million years. The impact event that thermally reset the K-Ar system of Asuka 881757 must have been post-Imbrium (perhaps Orientale) in age. The lead isotopic composition of Asuka 881757 is nonradiogenic compared with typical Apollo mare basalts and the estimated 238 U 204 Pb "> 238 U 204 Pb (μ) value for the basalt source is 10 ± 3. This source-μ value is the lowest so far measured for lunar rocks. A large positive ϵ Nd value (7.4 ± 0.5) and the time averaged 147 Sm 144 Nd "> 1 47 147 Sm 144 Nd "> Sm 144 Nd ratio for the basalt source are similar to those for some Apollo 12, 15, and 17 basalts, suggesting a LREE-depleted mantle, which is consistent with the global magma ocean hypothesis. The U-Th-Pb, Sm-Nd, and Rb-Sr data on Asuka 881757 suggest that the basalt was derived from a low U Pb "> UPb , low Rb Sr "> RbSr , and high Sm Nd "> SmNd source region, mainly composed of olivine and orthopyroxene with minor amounts of plagioclase (or clinopyroxene) and with sulfides enriched in volatile chalcophile elements. The basalt source may be deep in origin and different in chemistry from those previously estimated from studies of Apollo and Luna mare basalts, indicating heterogeneous sources for mare basalts.

Geochimica et Cosmochimica Acta↗

USGS1996

Organic geochemistry applied to environmental assessments of Prince William Sound, Alaska, after the Exxon Valdez oil spill—a review

Organic geochemistry played a major role in the environmental assessments conducted following the Exxon Valdez oil spill, which occurred on March 24, 1989, and released about 258,000 bbls (41 million liters) of Alaska North Slope crude oil into Prince William Sound. Geochemical analyses of more than 15,000 sediment, tar, and biological samples and about 5000 water samples provide the largest database yet collected on oil-spill chemistry, and we review the results here. The marine environment of the Sound has a complex background of petrogenic, pyrogenic, and biogenic hydrocarbons from natural and anthropogenic sources. Geochemical evaluation of the fate and effects of the spilled oil required that this oil and its residues be distinguished from the background. A variety of molecular and isotopic techniques were employed to identify various hydrocarbon sources and to distinguish quantitatively among mixed sources in the samples. Although the specific criteria used to distinguish multiple sources in the region affected by the Exxon Valdez spill are not necessarily applicable to all spill situations, the principles that governed their selection are. Distributions of polycyclic aromatic hydrocarbons (PAH) and dibenzothiophenes distinguish Exxon Valdez oil and its weathered residues from background hydrocarbons in benthic sediments. Ratios of C 2 -dibenzothiophene C 2 -phenanthrene "> C 2 -dibenzothiopheneC 2 -phenanthrene and C 3 -dibenzothiophene C 3 -phenanthrene "> C 3 -dibenzothiopheneC 3 -phenanthrene were particularly useful. Carbon isotopes and terpane distributions distinguished Exxon Valdez residues found on shorelines from tars from other sources. Diesel and diesel soot were identified by the absence of alkylated chrysenes and a narrow distribution of n -alkanes, whereas pyrogenic products were distinguished by the dominance of 4- to 6-ring PAH over 2- to 3-ring PAH and by the dominance of non-alkylated over alkylated homologues of each PAH series. The presence of 18α(H)-oleanane in benthic sediments, coupled with its absence in Exxon Valdez oil and its residues, confirm another petrogenic source. Results of geochemical studies suggest that the petrogenic component in the background of benthic sediments is derived from oil seeps in the eastern Gulf of Alaska. In 1990 and 1991, Exxon Valdez residues, generally forming a small increment to the pre-spill background, were found to be only sporadically distributed in some shallow, near shore sediments adjacent to shorelines that had been heavily oiled in 1989. In 1994, occurrences of Exxon Valdez tars on shoreline surfaces were rare, although residues could be found buried in shoreline sediments at some isolated locations along the spill path where they were protected from wave action. Spilled oil residues collected 16 months after the spill were degraded, on average, by nearly 50%. Shoreline residues from sources other than the spill were also identified and are widespread throughout the Sound. These residues include (1) geochemically distinct tars and oils imported from California oil fields to Alaska for fuel and construction purposes prior to the discovery of the Cook Inlet and North Slope oil fields, (2) diesel and diesel soot, and (3) more highly refined products. Of the more than 2700 chemical analyses of biological samples of higher life forms (fish, birds, and mammals) about 150 (6%) indicate recognizable residues of Exxon Valdez oil, which were identified by their distribution of polycyclic aromatic hydrocarbons (PAH). Most of these samples (138) were collected in 1989 and most were associated with external surfaces or the gastrointestinal tract. Rarely do internal tissues or fluids contain recognizable fingerprints of spilled oil. This observation includes samples from marine mammals that were visibly oiled externally. Other hydrocarbon sources, including diesel and a non-petroleum artifact that occurs when concentrations of individual PAH are at or near their method detection limit, are also identified in biological samples.

Alaska↗

USGS1998

Overview of a workshop on screening methods for detecting potential (anti-) estrogenic/androgenic chemicals in wildlife

The U.S. Congress has passed legislation requiring the U.S. Environmental Protection Agency (U.S. EPA) to develop, validate, and implement screening tests for identifying potential endocrine-disrupting chemicals within 3 years. To aid in the identification of methods suitable for this purpose, the U.S. EPA, the Chemical Manufacturers Association, and the World Wildlife Fund sponsored several workshops, including the present one, which dealt with wildlife species. This workshop was convened with 30 international scientists representing multiple disciplines in March 1997 in Kansas City, Missouri, USA. Participants at the meeting identified methods in terms of their ability to indicate (anti-) estrogenic/androgenic effects, particularly in the context of developmental and reproductive processes. Data derived from structure-activity relationship models and in vitro test systems, although useful in certain contexts, cannot at present replace in vivo tests as the sole basis for screening. A consensus was reached that existing mammalian test methods (e.g., with rats or mice) generally are suitable as screens for assessing potential (anti-) estrogenic/ androgenic effects in mammalian wildlife. However, due to factors such as among-class variation in receptor structure and endocrine function, it is uncertain if these mammalian assays would be of broad utility as screens for other classes of vertebrate wildlife. Existing full and partial life-cycle tests with some avian and fish species could successfully identify chemicals causing endocrine disruption; however, these long-term tests are not suitable for routine screening. However, a number of short-term tests with species from these two classes exist that could serve as effective screening tools for chemicals inducing (anti-) estrogenic/androgenic effects. Existing methods suitable for identifying chemicals with these mechanisms of action in reptiles and amphibians are limited, but in the future, tests with species from these classes may prove highly effective as screens. In the case of invertebrate species, too little is known at present about the biological role of estrogens and androgens in reproduction and development to recommend specific assays.

Environmental Toxicology and Chemistry↗

USGS2004

Mineral matter and potentially hazardous trace elements in coals from Qianxi Fault Depression Area in southwestern Guizhou, China

Mineralogy, coal chemistry and 21 potentially hazardous trace elements (PHTEs) of 44 coal samples from the Qianxi Fault Depression Area (QFDA) in southwestern Guizhou province, China have been systematically studied. The major minerals in coals studied are quartz, kaolinite, illite, pyrite, calcite, smectite, marcasite and accessory minerals, including rutile, dolomite, siderite, gypsum, chlorite, melanterite, apatite, collophane and florencite. The SiO2 content shows a broad variation (0.8-30.7%). A high SiO2 content in Late Permian coals reflects their enrichment in quartz. The Al2O3 content varies from 0.8% to 13.4%, Fe2O3 from 0.2% to 14.6%, CaO from <0.1% to 11.9% and the contents of other oxides are relatively low. The relationship between the major oxides and the ash content of coals from high to low is in the order of Si>Al>K>Ti>Na>Mg>Ca>Fe>S. A comparison with World coal averages shows that the Late Permian coals in QFDA are highly enriched in As, Hg, F and U, and are slightly enriched in Mo, Se, Th, V and Zn. The Late Triassic coals in QFDA are highly enriched in As and Hg, and are slightly enriched in Mo, Th and U. The concentrations of As, Hg, Mo, Se, Tl and Zn in the QFDA coal are higher than other Guizhou coal and Liupanshui coal nearby. The QFDA is an area strongly affected by the low-temperature hydrothermal activity during its geologic history (Yanshanian Age, about 189 Ma). The coals in QFDA are enriched in volatile PHTEs, including As, Hg, Se, Sb, Mo, among others. The regions where the coals are enriched in As, Hg and F have been mapped. The regions of coals enriched in volatile PHTEs overlap with the regions of noble metal ore deposits. These coals are located in the cores of anticline and anticlinorium, which are connected with the profound faults through the normal faults. Coals are enriched in volatile PHTEs as a result of the low-temperature hydrothermal activity associated with tectonic faulting. ?? 2003 Elsevier B.V. All rights reserved.

International Journal of Coal Geology↗

USGS2014

Two hundred years of magma transport and storage at Kīlauea Volcano, Hawai'i, 1790-2008

This publication summarizes the evolution of the internal plumbing of Kīlauea Volcano on the Island of Hawaiʻi from the first documented eruption in 1790 to the explosive eruption of March 2008 in Halemaʻumaʻu Crater. For the period before the founding of the Hawaiian Volcano Observatory in 1912, we rely on written observations of eruptive activity, earthquake swarms, and periodic draining of magma from the lava lake present in Kīlauea Caldera. After 1912 the written observations are supplemented by continuous measurement of tilting of the ground at Kīlauea’s summit and by a continuous instrumental record of earthquakes, both measurements made during 1912–56 by a single pendulum seismometer housed on the northeast edge of Kīlauea’s summit. Interpretations become more robust following the installation of seismic and deformation networks in the 1960s. A major advance in the 1990s was the ability to continuously record and telemeter ground deformation to allow its precise correlation with seismic activity before and after eruptions, intrusions, and large earthquakes. We interpret specific events in Kīlauea’s 200- year written history as steps in a broad transition from summit lava-lake activity in Kīlauea Caldera to shield building on the east rift zone. The ability of the magmatic plumbing to deliver magma to eruption is critical to the history of eruption and intrusion. When the rate of magma supply equals the rate of eruption, there is little ground deformation or intrusion. When the magma supply rate is greater than the rate of eruption, then the edifice responds through any or all of summit inflation, intrusion, increased spreading rate, and large flank earthquakes. In Kīlauea’s 200-year history we identify three regions of the volcano in which magma is stored and supplied from below. Source 1 is at 1-km depth or less beneath Kīlauea’s summit and fed Kīlauea’s summit lava lakes throughout most of the 19th century and again from 1907 to 1924. Source 1 was used up in the series of small Halemaʻumaʻu eruptions following the end of lava-lake activity in the summit collapse of 1924. Source 2 is the magma reservoir at a depth of 2–6 km beneath Kīlauea’s summit that has been imaged by seismic and deformation measurements beginning in the 1960s. This source was first identified in the summit collapses of 1922 and 1924. Source 3 is a diffuse volume of magma-permeated rock between 5 and 11 km depth beneath the east rift zone and above the near-horizontal decollement at the base of the Kīlauea edifice. Magma distribution within source 2 has been derived by combining petrologic study of the three chemically uniform summit eruptions of 1952, 1961, and 1967–68 and the east rift eruptions within this interval with both observation of migrating centers of inflation determined from leveling surveys conducted before the 1967–68 eruption and with published models of expected deformation from different source geometries. We adopt a model of concatenated magmatic plugs with nodes beneath the inflation centers. Addition of erupted and intruded volumes of the three summit magma batches yields a liquid magma volume of about 0.2 km3, with dimensions of ~1 km by 1 km by 200 m centered at about 3-km depth within source 2. Following the Halemaʻumaʻu eruption of 1967–68, the chemistry of magma coming into Kīlauea’s summit reservoir has changed frequently, and during the eruption that began in 1983, chemical changes have been subtle and continuous. In this period we interpret changes in chemistry as related to an increase in magma supply resulting from increased partial melting in an expanding mantle source volume. We know from instrumental recording of eruptions since the long Halemaʻumaʻu eruption in 1952 that stress in the edifice accumulates as magma is added underground and is relieved by eruption and by dilation of the rift zones associated with seaward movement (spreading) of Kīlauea’s south flank. During and after the last half of the 20th century, magma transfer to the rift zone has dominantly occurred from source 2. High rates of flank motion have been correlated with high rates of endogenous growth; alternatively, lower rates of motion have characterized periods when the underground magmatic plumbing was being refilled following lateral removal of magma, as well as periods when a more open magmatic plumbing favored continuous eruption. Since at least 1952, source 3 has not drained during deflations, which was apparently not the case before 1924. Triangulation and leveling conducted in 1912, 1921, and 1926, combined with post-1912 tilt measurements, identified a broad regional uplift in 1918–19 and an equally broad collapse in 1924, neither of which has been seen since. We associate these elevation changes with addition or subtraction of magma from all three magma sources, dominantly source 3. We interpret the intrusion beneath the east rift zone during the 1924 collapse to have stabilized the rift zone-south flank relationship, preventing loss of magma from source 3 in subsequent collapses. Rates of seaward spreading were low until 1952, when earthquakes in 1950 and 1951 associated with surges of magma from the hotspot triggered a large offshore south flank earthquake swarm that unlocked the south flank and enabled a greatly increased rate of seaward spreading. Magma supply rates have been derived for the entire period of study. Between 1823 and 1840, magma was supplied from source 1 at a very high rate of more than 0.2 km 3 /yr, which we interpret as recovery from a substantial draining of magma from beneath Kīlauea in 1790. Inferred magma supply rates diminished to one-tenth of that value after 1840, in part because of increase in the activity of Mauna Loa beginning in 1843. Magma supply rates between 1918 and 1924 were about 0.024 km 3 /yr, matching that of the period from 1840 to 1894. During 1950–52 the magma supply rate increased to about 0.06 km 3 /yr, in part because of the great reduction in Mauna Loa activity following its large eruption in June 1950. Following the summit eruption of 1967–68, magma supply increased further to ~0.1 km 3 /yr, and further increases to more than 0.2 km 3 /yr occurred during the east rift eruption that began in 1983. Eruption at Kīlauea’s summit took place in 1952, and eruptive activity steadily increased as increased magma supply also drove increased spreading rates. The inability of magma supply to be accommodated by a combination of eruption and spreading during the 1969–74 Mauna Ulu period stressed Kīlauea’s south flank. The stress was relieved in part by the M7.2 earthquake of 29 November 1975. That earthquake, in turn, dilated Kīlauea’s east rift zone as the south flank moved seaward, producing a favorable condition for continuous east rift eruption, which began in 1983. The 1975 earthquake also resulted in the ability of the south flank to move independently under the influence of gravity, effectively decoupling the spreading rate from changes in the magma supply rate. The continuing increase in magma supply after 1983 was instead manifested in rift dilation, increased intrusion, and ultimately in the launching of a second eruption in Halemaʻumaʻu in March 2008, the first instance in Kīlauea’s recorded history of simultaneous eruption at the summit and on the east rift zone. Kīlauea’s history can be considered in cycles of equilibrium, crisis, and recovery. The approach of a crisis is driven by a magma supply rate that greatly exceeds the capacity of the plumbing to deliver magma to the surface. Crises can be anticipated by inflation measured at Kīlauea’s summit coupled with an increase in overall seismicity, particularly manifest by intrusion and eruption in the southwest sector of the volcano. Unfortunately the nature of the crisis—for example, large earthquake, new eruption, or edifice-changing intrusion—cannot be specified ahead of time. We conclude that Kīlauea’s cycles are controlled by nonlinear dynamics, which underscores the difficulty in predicting eruptions and earthquakes.

Hawai'i↗

USGS2006

Petrology and chemistry of Permian coals from the Paraná Basin: 1. Santa Terezinha, Leão-Butiá and Candiota Coalfields, Rio Grande do Sul, Brazil

The current paper presents results on petrological and geochemical coal seam characterization in Permian coal-bearing strata from the Paraná Basin, southern Brazil. Sequence stratigraphic analysis shows that peat accumulation in Permian time was closely linked to transgressive/regressive cycles, with peat accumulation occurring in a predominantly back barrier/lagoonal setting. Coal petrographic analysis indicates subbituminous coals at Candiota and Leão-Butiá and high volatile bituminous coals at Santa Terezinha, where locally the coal seams are thermally altered by volcanic intrusions. Petrographic composition is highly variable, with seams at Candiota and Santa Terezinha frequently enriched in inertinite. Chemical analyses indicate that all coals are mineral matter-rich (mean 49.09 wt.%), with SiO 2 and Al 2 O 3 dominating as determined by ICP-AES. Quartz is also the predominant mineral detected by X-ray diffraction, where it is associated with feldspar, kaolinite and hematite and iron-rich carbonates. The results from Scanning Electron Microscopy are broadly consistent with the bulk chemical and mineralogical analysis. Quartz and clays are common in all samples analyzed. Other minerals observed were, amongst others, carbonates (calcite, siderite, ankerite), pyrite, monazite, kaolinite, barite, sphalerite, rutile and quartz of volcanic origin. The distribution of trace elements is well within the range typical for coal basins of other areas despite the fact that the Paraná Basin coals are very high in ash yields. The average concentrations for elements of environmental concern (As, B, Be, Cd, Co, Cr, Cu, Hg, Li, Mn, Mo, Ni, Pb, Sb, Se, Tl, U, V, Zn) are similar to or less than the mean values for U.S. coal. However, considered on an equal energy basis, Paraná Basin coals will produce in combustion 5 to 10 times the amount of most elements compared to an equal weight US coal. Concentrations of major and trace elements, such as Fe, B and S, appear to be controlled by depositional setting, with increasing values in coal seams overlain by brackish/marine strata. Hierarchical cluster analysis identified three groups of major minerals and seven groups of trace elements based on similarity levels. On a regional scale, the coalfields can be separated by the differences in rank (Candiota and Leão-Butiá versus Santa Terezinha) and by applying discriminant analysis based on 4 trace elements (Li, As, Sr, Sb). Highest Rb and Sr values occur at Candiota and are linked to syngenetic volcanism of the area, whereas high Y and Sr values at Santa Terezinha can be related to the frequent diabase intrusions in that area.

International Journal of Coal Geology↗

USGS2010

Polybaric evolution of phonolite, trachyte, and rhyolite volcanoes in eastern Marie Byrd Land, Antarctica: Controls on peralkalinity and silica saturation

In the Marie Byrd Land volcanic province, peralkaline and metaluminous trachytes, phonolites, and rhyolites occur in 18 large shield volcanoes that are closely associated in time and space. They are arrayed radially across an 800 km wide structural dome, with the oldest at the crest and the youngest around the flanks. Several lines of evidence suggest that these rocks evolved via opensystem, polybaric fractionation. We have used mass balance modeling of major elements together with trace-element data and mineral chemistry to help explain the evolution of this diverse suite of felsic rocks, which appear to have been generated coevally in isolated magma chambers, and erupted close to each other in patterns related to tectonic uplift and extension within the West Antarctic rift system. Isotopic and trace-element data indicate that this occurred with only minimal crustal contamination. We focus on volcanoes of the Executive Committee Range and Mount Murphy, where we find good representation of basalts and felsic rocks within a small area. Our results suggest that the felsic rocks were derived from basaltic magmas that differentiated at multiple levels during their passage to the surface: first to ferrogabbroic compositions near the base of the lithosphere, then to intermediate compositions near the base of the crust, and finally to felsic compositions in mid- to upper crustal reservoirs. The high-pressure history has been largely masked by low-pressure processes. The best indications of a high-pressure history are the mineral phases in cumulate nodules and their correlation with modeling results, with REE anomalies, and with the composition of an unusual gabbroic intrusion. Silica saturation characteristics are believed to have originated in magma chambers near the base of the crust, via fractionation of variable proportions of kaersutite and plagioclase. Development of peralkalinity in felsic rocks took place in upper crustal reservoirs by fractionating a high ratio of plagioclase to clinopyroxene under conditions of low pH 2 O. With increasing pH 2 O, the ratio plagioclase/clinopyroxene in the fractionated assemblage decreases and metaluminous liquids resulted. Crustal contamination seems to have had a role in suppressing peralkalinity , and was probably a factor in the origin of high- silica metaluminous rhyolite , but metaluminous rocks are uncommon. The volume and diversity of felsic rocks were probably enhanced by the structure of the lithosphere, the persistence of plume activity, and the immobility of the Antarctic plate. Mechanical boundaries at the base of the lithosphere and crust, and within the crust, appear to have acted as filters, trapping magmas at multiple levels, and prolonging the fractionation process. Final volumes would have been further enhanced by repeated refluxing of the same magma chambers, controlled by plume activity and plate immobility.

International Geology Review↗

USGS1989

The geology, botany and chemistry of selected peat-forming environments from temperate and tropical latitudes

Peat has been studied in several geologic settings: (1) glaciated terrain in cold temperate Maine and Minnesota, U.S.A.; (2) an island in the Atlantic Ocean off the coast of Maine, where sea level is rising; (3) the warm temperate U.S. Atlantic and Gulf Coastal Plains, where sea level has changed often; and (4) the tropical coast of Sarawak, Malaysia, and the tropical delta of the Batang Hari River, Sumatra, Indonesia. Most of these deposits are domed (ombrotrophic or partly ombrotrophic) bogs in which peat accumulation continued above the surface of the surrounding soil. However, the bogs of the U.S. Atlantic and Gulf Coastal Plains are comparatively not as domed, and many have almost level surfaces. In some bogs, aquatic or semi-aquatic plant materials accumulated, replaced water in the depressions, and formed a surface on which marsh or swamp vegetation could subsequently live, die, and accumulate. In others, the plant materials accumulated initially on level silt or sand surfaces supporting marshes or swamps. As the peat dome formed, plants growing on it changed from luxuriant ones near the base of the dome, where nutrients were brought into the bog by surface and ground water, to stunted ones at the top of the dome, where the raised bogs are fed by nutrient-poor precipitation. The physical and chemical changes that take place in the sequence of environments from the pond stage of deposit development, through the grassy marsh stage, through the forested swamp stage, and finally through the heath dome stage can be measured in terms of acidity and ash, volatile matter, carbon, hydrogen, nitrogen, sulfur and oxygen contents, as well as in the kind and distribution of trace elements. The organic and inorganic contents of the deposits relate to geomorphology, and geomorphology relates to their settings. As models of coal formation, some domed peat deposits may help in solving problems of distribution and character of ancient coal beds. But clearly not all peat deposits are precursors of coal. Most Holocene peat deposits are subject to destruction by erosion, fire and decomposition through microbial and chemical oxidation before burial. The best environments for coal precursors have biomass accumulation, a continuously rising water table within the mass, and minimum influx of clay and silt until preservation by burial. The most suitable settings for future economic coal deposits are domed bogs that accumulate thick, widespread peat having low ash and low sulfur contents. The ombrotrophic peat deposits of tropical Sarawak and Sumatra are thick and extensive, contain low-ash and low-sulfur peat, and have high heating values. They are considered to be the best tropical coal analogs because of their extent and chances of preservation; the base of the peat is below adjacent river levels, and chemical and structural conditions are favorable for accumulation.

International Journal of Coal Geology↗

USGS2012

Geochemical modeling of changes in shallow groundwater chemistry observed during the MSU-ZERT CO2 injection experiment

A field experiment involving the release of carbon dioxide (CO 2 ) into a shallow aquifer was conducted near Bozeman, Montana, during the summer of 2008, to investigate the potential groundwater quality impacts in the case of leakage of CO 2 from deep geological storage. As an essential part of the Montana State University Zero Emission Research and Technology (MSU-ZERT) field program, food-grade CO 2 was injected over a 30 day period into a horizontal perforated pipe a few feet below the water table of a shallow aquifer. The impact of elevated CO 2 concentrations on groundwater quality was investigated by analyzing water samples taken before, during, and following CO 2 injection, from observation wells located in the vicinity of the injection pipe, and from two distant monitoring wells. Field measurements and laboratory analyses showed rapid and systematic changes in pH, alkalinity, and conductance, as well as increases in the aqueous concentrations of naturally occurring major and trace element species. The geochemical data were evaluated using principal component analysis (PCA) to (1) understand potential correlations between aqueous species, and (2) to identify minerals controlling the chemical composition of the groundwater prior to CO 2 injection. These evaluations were used to assess possible geochemical processes responsible for the observed increases in the concentrations of dissolved constituents, and to simulate these processes using a multicomponent reaction path model. Reasonable agreement between observed and modeled data suggests that (1) calcite dissolution was the primary pH buffer, yielding increased Ca +2 concentrations in the groundwater, (2) increases in the concentrations of most major and trace metal cations except Fe could be a result of Ca +2 -driven exchange reactions, (3) the release of anions from adsorption sites due to competitive adsorption of carbonate could explain the observed trends of most anions, and (4) the dissolution of reactive Fe minerals (presumed ferrihydrite and fougerite, from thermodynamic analyses) could explain increases in total Fe concentration. Highlights ► Because the possibility of CO 2 leakage cannot be completely ruled out, the potential impact of CO 2 intrusion on the quality of fresh water aquifers overlying CO 2 storage sites needs to be investigated. ► Geochemical data from a field experiment involving the release of carbon dioxide (CO 2 ) into a shallow aquifer were evaluated. ► Geochemical model used to assess possible geochemical processes responsible for the observed increases in the concentrations of dissolved constituents. ► Reasonable agreement between observed and modeled data suggests that increases in the concentrations of most major and trace metal cations except Fe could be a result of Ca +2 -driven exchange reactions and the release of anions from adsorption sites due to competitive adsorption of carbonate could explain the observed trends of most anions.

Montana↗

USGS2024

Evaluation of chronic effects of potassium chloride and nickel on survival, growth, and reproduction of a unionid mussel (Lampsilis siliquoidea)

The ASTM International standard test method for freshwater mussels (E2455‐13) recommends 4‐week toxicity testing with juveniles to evaluate chronic effects on survival and growth. However, concerns remain that the method may not adequately address the sensitivity of mussels to longer term exposures (>4 weeks), particularly in relation to potential reproductive impairments. No standard method directly evaluates toxicant effects on mussel reproduction. The objectives of the present study were to (1) evaluate toxicity endpoints related to reproduction in fatmucket ( Lampsilis siliquoidea ) using two common reference toxicants, potassium chloride (KCl) and nickel (Ni); (2) evaluate the survival and growth of juvenile fatmucket in standard 4‐week and longer term (12‐week) KCl and Ni tests following a method refined from the standard method; and (3) compare the sensitivity of the reproductive endpoints with the endpoints obtained from the juvenile mussel tests. Reproductive toxicity tests were conducted by first exposing female fatmucket brooding mature larvae (glochidia) to five test concentrations of KCl and Ni for 6 weeks. Subsamples of the glochidia were then removed from the adults to determine three reproductive endpoints: (1) the viability of brooded glochidia; (2) the viability of free glochidia in a 24‐h exposure to the same toxicant concentrations as their mother; and (3) the success of glochidia parasitism on host fish. Mean viability of brooded glochidia was significantly reduced in the high KCl concentration (26 mg K/L) relative to the control, with a 20% effect concentration (EC20) of 14 mg K/L, but there were no significant differences between the control and any Ni treatment (EC20 > 95 µg Ni/L). The EC20s for viability of free glochidia after the additional 24‐h exposure and parasitism success were similar to the EC20s of brooded glochidia. The EC20s based on the most sensitive biomass endpoint in the 4‐week juvenile tests were 15 mg K/L and 91 µg Ni/L, similar to or greater than the EC20s from the reproductive KCl and Ni tests, respectively. When exposure duration in the juvenile tests was extended from 4 to 12 weeks, the EC20s decreased by more than 50% in the KCl test but by only 8% in the Ni test. Overall, these results indicate that a standard 4‐week test with juvenile mussels can prove effective for estimating effects in chronic exposures with different life stages although a longer term 12‐week exposure with juvenile mussels may reveal higher sensitivity of mussels to some toxicants, such as KCl.

Environmental Toxicology and Chemistry↗