Composition of altered oceanic crust at ODP Sites 801 and 1149

Kelley, K. A.; Plank, Terry; Ludden, John; Staudigel, Hubert

doi:10.1029/2002gc000435

Cited by 453 publications

(405 citation statements)

References 41 publications

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“…(1) Weyer et al (2002), (2) Eggins et al (1997), (3) Ishikawa and Nakamura (1994), (4) Lu et al (2007), (5) Kelley et al (2003), (6) Imai et al (1995). …”

Section: Icp-ms Measurementmentioning

confidence: 99%

A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples

Nagaishi

Ishikawa

2009

Geochem. J.

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An analytical technique for determining boron, zirconium, niobium, hafnium and tantalum contents in rock samples by inductively coupled plasma mass spectrometry (ICP-MS) is described. The rock samples (<30 mg) were decomposed with mannitol-added HF, and dissolved in a 0.015 M HF/0.12 M HNO 3 acid mixture for ICP-MS analysis. Boron, zirconium, niobium, hafnium and tantalum concentrations were measured by the internal calibration curve method using three internal standard elements, beryllium for boron, indium for zirconium and niobium, and rhenium for hafnium and tantalum. Seventeen rock reference samples from the Geological Survey of Japan and the U.S. Geological Survey were analyzed, and the determined concentrations showed good agreement with the reported values obtained by isotope dilution method, as well as with the recommended values. This technique is a simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum concentrations, and it has wide potential for geochemical application, particularly for the determination of boron.Keywords: ICP-MS, analytical method, rock reference samples, boron, high field strength elements 1990; Ishikawa and Nakamura, 1994;Ishikawa and Tera, 1997;Tonarini et al., 2001). Although the isovalent element pairs zirconium-hafnium and niobium-tantalum have very similar ionic radii and generally behave coherently during magmatic processes, the Zr/Hf and Nb/Ta ratios of some mantle-derived igneous rocks deviate sub-

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“…(1) Weyer et al (2002), (2) Eggins et al (1997), (3) Ishikawa and Nakamura (1994), (4) Lu et al (2007), (5) Kelley et al (2003), (6) Imai et al (1995). …”

Section: Icp-ms Measurementmentioning

confidence: 99%

A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples

Nagaishi

Ishikawa

2009

Geochem. J.

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“…Resulting sample solutions were evenly divided for trace element and isotopic analyses. Trace element solutions were converted to HNO 3 , diluted, and analyzed on the VG PQIIXS quadrupole ICP-MS at Boston University, following the procedures outlined by Kelley et al [2003] Rioux et al [2007]. Major element analyses were carried out on fused samples by inductively coupled plasma-atomic emission spectrometry (ICP-AES) at Boston University, following the procedure outlined by Kelley et al [2003].…”

Section: Analytical Techniquesmentioning

confidence: 99%

Intermediate to felsic middle crust in the accreted Talkeetna arc, the Alaska Peninsula and Kodiak Island, Alaska: An analogue for low‐velocity middle crust in modern arcs

et al. 2010

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Seismic profiles of several modern arcs have identified thick, low‐velocity midcrustal layers (Vp = 6.0–6.5 km/s) that are interpreted to represent intermediate to felsic plutonic crust. The presence of this silicic crust is surprising given the mafic composition of most primitive mantle melts and could have important implications for the chemical evolution and bulk composition of arcs. However, direct studies of the middle crust are limited by the restricted plutonic exposures in modern arcs. The accreted Talkeetna arc, south central Alaska, exposes a faulted crustal section from residual subarc mantle to subaerial volcanic rocks of a Jurassic intraoceanic arc and is an ideal place to study the intrusive middle crust. Previous research on the arc, which has provided insight into a range of arc processes, has principally focused on western exposures of the arc in the Chugach Mountains. We present new U‐Pb zircon dates, radiogenic isotope data, and whole‐rock geochemical analyses that provide the first high‐precision data on large intermediate to felsic plutonic exposures on Kodiak Island and the Alaska Peninsula. A single chemical abrasion–thermal ionization mass spectrometry analysis from the Afognak pluton yielded an age of 212.87 ± 0.19 Ma, indicating that the plutonic exposures on Kodiak Island represent the earliest preserved record of Talkeetna arc magmatism. Nine new dates from the extensive Jurassic batholith on the Alaska Peninsula range from 183.5 to 164.1 Ma and require a northward shift in the Talkeetna arc magmatic axis following initial emplacement of the Kodiak plutons, paralleling the development of arc magmatism in the Chugach and Talkeetna mountains. Radiogenic isotope data from the Alaska Peninsula and the Kodiak archipelago range from ɛNd(t) = 5.2 to 9.0 and 87Sr/86Srint = 0.703515 to 0.703947 and are similar to age‐corrected data from modern intraoceanic arcs, suggesting that the evolved Alaska Peninsula plutons formed by extensive differentiation of arc basalts with little or no involvement of preexisting crustal material. The whole‐rock geochemical data and calculated seismic velocities suggest that the Alaska Peninsula represents an analogue for the low‐velocity middle crust observed in modern arcs. The continuous temporal record and extensive exposure of intermediate to felsic plutonic rocks in the Talkeetna arc indicate that evolved magmas are generated by repetitive or steady state processes and play a fundamental role in the growth and evolution of intraoceanic arcs.

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“…Figure 2a (Kelley et al, 2003) shows that as the oceanic crust ages and interacts with sea-water and is oxidized, its U content increases. The original composition of U in the crust is about 0.2 ppm and with oxidation increases can be greater than ten-fold.…”

Section: The U/pb Ratio Of Altered Recycled Basaltic Oceanic Crustmentioning

confidence: 99%

Subduction fluxes through geologic time

Ludden

2009

Applied Geochemistry

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Much of my research career has been spent working both on modern oceanic volcanic systems and at the same time looking at their Archaean counterparts. Many authors have attempted to make inferences on early Earth models based on modern processes which can be increasingly well constrained. In this short review I show how we are beginning to understand and quantify inputs to modern subduction systems and I pose some questions as to how these processes may have affected Earth's evolution in its distant past.Geochemical models have convincingly demonstrated that sediment and altered oceanic crust must be recycled into the mantle through subduction zones. These 'subduction factories' use these components, along with molten mantle, to create arc magmas. The 'residue' from this process is recycled into the mantle and has a modified chemical and mineralogical composition. The altered oceanic crust input function in the current plate tectonic cycle seems to be relatively constant in composition, but the chemical compositions of the sediment fluxes into subduction zones vary widely and control many of the end-member compositions of arc magmas. They must also control the compositions of fluids and gases derived from these magmas and ultimately ore-deposition and atmospheric fluxes associated with arc volcanoes.There is relatively strong evidence for subduction processes for at least the past 3.5 Ma and some would argue that exogenic components have been recycled into the mantle since at least ~4.3 Ma. How might the subduction fluxes have changed through time, and how might they have influenced crust, ocean and atmospheric compositions?Can different ore regimes in temporal and spatial distribution on Earth be related to the change in inputs and residues from the subduction factory through time?

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Composition of altered oceanic crust at ODP Sites 801 and 1149

Cited by 453 publications

References 41 publications

A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples

A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples

Intermediate to felsic middle crust in the accreted Talkeetna arc, the Alaska Peninsula and Kodiak Island, Alaska: An analogue for low‐velocity middle crust in modern arcs

Subduction fluxes through geologic time

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