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Results for “Trace Elements Investigations”

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At least 685 records · Page 38Linked to original sources
USGS1950

Beryllium in Colorado

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Trace Elements Investigations↗
USGS2026

Magmatic source of the opening phase of Kīlauea’s 2018 Lower East Rift Zone eruption

The 2018 eruption of Kīlauea volcano in its Lower East Rift Zone began with the discharge of evolved high-Ti basalt as weak lava fountains and short, slow-moving lava flows. The lavas were quickly geochemically recognized as being derived from magmas stored within the rift zone and remobilized by a new intrusion, a sequence that is common at Kīlauea. This initial phase of the 2018 eruption, referred to as phase 1a, lasted for 6 days and was followed by extrusion of mixed magma after a 3-day pause. Even though remobilization of older rift zone magmas is common within Kīlauea’s rift zones, it is difficult to determine which past intrusion(s) may have initially emplaced those stored magmas. This difficulty stems from the tendency for Kīlauea magmas to follow very similar differentiation paths without significant variations in major, minor, or even trace element chemistry. We investigate possible magma sources for the lavas erupted during phase 1a of the 2018 eruption using whole-rock, mineral, and glass major and trace element compositions from historical East Rift Zone eruptions with adjacent fissures. We consider two primary hypotheses for the phase 1a source: magmas associated with the 1955 Lower East Rift Zone eruption or the nine eruptions in the Middle and Upper East Rift Zone during the 1960s. Our results suggest that magma associated with the earliest phases of Kīlauea’s 1955 eruption was the most likely source of the 2018 phase 1a remobilized magma. We determine volatile saturation pressures from melt inclusion chemistry and find similar storage depths for the 2018 phase 1a and early 1955 magmas. The phase 1a and early 1955 lavas are nearly indistinguishable in all of the compositional criteria considered, implying that the leftover 1955 magma body barely cooled and differentiated in the 63 years between eruptions (cooling rates of ~0.1 °C/year). This study sheds light on the potential for protracted storage of eruptible magmas in rift zones at Kīlauea, and highlights some of the challenges and solutions to identifying genetic relationships between magmas at Kīlauea.

Hawaii↗
USGS1994

Water-quality, lithologic, and water-level data for wells in Tulare Basin, Kings, Kern, and Tulare Counties, California, August 1990 to February 1993

Much of the Tulare Basin is characterized by saline shallow ground water containing elevated concen- trations of arsenic, selenium, and other trace elements. A comprehensive investigation of ground-water geochemist, and, to a limited extent, hydrology was initiated in response to concerns related to (1) adverse effects on migratory waterfowl of high concentrations of selenium in agricultural drainwater disposed of in evaporation ponds and (2) adverse effects on human health due to potential downward migration of ground water containing high concentrations of arsenic to regional aquifers used as drinking-water sources. This report presents data collected during the initial phase of this investigation. A total of 20 observation wells were installed at 5 locations in the basin. Four observation wells in a cluster were installed at each location at depths of about 20, 50, 100, and 200 feet. Water samples collected from each site were analyzed for major ions, trace elements (including arsenic and selenium), nutrients, and selected isotopes. Lithologic logs and well-construction information for each site and water-level measurements for each well measured periodically from August 1990 to February 1993 also are reported.

Open-File Report↗
USGS1985

Element mobility studies of two drill-cores from the Götemar Granite (Kråkemåla test site), southeast Sweden

A pilot study was carried out on two relatively deep drill-cores (∼ 600 m) from the Götemar Granite massif in S.E. Sweden. This granite is typical of the 1400-Ma anorogenic granites of the northern hemisphere. Samples from representative, unfractured parts of the cores, together with four samples taken along a profile tangential to a fracture plane at ∼ 280-m depth, were investigated chemically, mineralogically and isotopically. The results show that after crystallisation, subtle and pervasive open-system modifications of the trace-element chemistry of the granite took place. Whereas the major-element chemistry and minera-logical data emphasised the relative homogeneity of the Götemar Granite samples investigated, trace elements such as U, Rb, and Pb revealed irregular distributions which are probably the result of large-scale hydrothermal alteration processes. This conclusion is supported by isotopic studies which indicate that whole-rock samples were open to a gain or loss of Pb and possibly U at ∼ 420 ± 171 Ma ago. In addition, isotopic data for U-Pb and U-Ra are consistent with a recent minor loss of U. The pervasive alteration and the more recent mobilisation of U are evident to a depth of at least 600 m. The effects are most prevalent along major fracture zones and within the upper 250–300 m of one drill-hole where a high frequency of crush zones has been noted. Higher Fe oxidation ratios, higher Rb contents, lower U contents and correspondingly higher Th/U ratios, all characterise this zone.

Chemical Geology↗
USGS2026

Constraining the onset of carboniferous cyclicity in the Arkoma Basin of the Midcontinent, North America: Implications for calibrating a globally significant latest Bashkirian transgression

Cyclothems are defined by the repeat juxtaposition of littoral and open marine successions over short stratigraphic distances (meters to 10's of meters) and are interpreted to be driven by glacioeustatic forcing of sea level during the late Paleozoic Ice Age. The concept of cyclothems was defined in the Midcontinent region of the United States. However, correlating the Midcontinent region to other cyclic successions is difficult, which is the result of no geochronologic control for the Midcontinent biostratigraphic framework. We present the first high-resolution U Pb zircon CA-ID-TIMS and feldspar 40 Ar/ 39 Ar age control for the onset of Midcontinent cyclothem deposition in the Arkoma Basin, Arkansas USA. Geochronologic control is obtained from a volcaniclastic unit preserved in the newly recovered Dare Creek #1 core. We integrate these data with biostratigraphic, lithostratigraphic and trace element analyses to investigate the timing, stratigraphic and geochemical response to late Paleozoic climate forcing. The lowermost Atoka Formation is associated with the onset of five high frequency transgressive-regressive cycles, which are defined by nearshore sandstones juxtaposed on top of offshore marine mudstones and are associated with changes in salinity and redox conditions. The Trace Creek Member of the lower Atoka Formation hosts a thick, organic-rich black shale, which defines the last and maximum transgression of the lower Atoka Formation in the Arkoma Basin, in the latest Bashkirian. Base-level records from time equivalent stratigraphic successions from Arrow Canyon, Nevada, U.S.A. and the Donets Basin, Ukraine also record a maximum transgression in the latest Bashkirian. The synchroneity of maximum flooding events from multiple basins which span the low latitudes in the latest Bashkirian support that cyclothem deposition was controlled by allostratigraphic forcing mechanisms, likely glacioeustatic forcing resulting from dynamic glaciation in high-latitude Gondwana.

Arkansas, Oklahoma↗