Reply to Boslough: Is Greenland Pt anomaly global or local?
PNAS 110(52):E5036 (2013)
Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas.
PNAS 110(32):12917 (2013)
One explanation of the abrupt cooling episode known as the Younger Dryas (YD) is a cosmic impact or airburst at the YD boundary (YDB) that triggered cooling and resulted in other calamities, including the disappearance of the Clovis culture and the extinction of many large mammal species. We tes...
Fe–Al-rich tridymite–hercynite xenoliths with positive cerium anomalies: preserved lateritic paleosols and implications for Miocene climate
Chemical Geology 207(1):101 (2004)
We report isotopic and chemical compositions of unusual tridymite–hercynite xenoliths in middle Miocene Niutoushan tholeiites from the southeast coastal area of China. These xenoliths are characterized by positive cerium (Ce) anomalies and extremely high Al
3 (32–34 wt.%) and...
Constraints on melt movement beneath the East Pacific Rise from 230Th-238U disequilibrium.
Science 295(5552):107 (2002)
We report 230Th-238U disequilibrium data on mid-ocean ridge basalts recovered 5 to 40 kilometers off the ridge axis near 9 degrees 30'N of the East Pacific Rise. These data indicate near-symmetrical eruptions of normal mid-ocean ridge basalts (NMORBs) and incompatible element-enriched mid-ocean ...
Major, trace element, and Nd, Sr and Pb isotope studies of Cenozoic basalts in SE China: mantle sources, regional variations, and tectonic significance
Chemical Geology 171(1):33 (2000)
Major, trace element, and Nd–Sr–Pb isotopic compositions of mantle xenolith-bearing Cenozoic basalts in southeastern China are measured to provide an insight into the nature of their mantle sources and processes. Application of a modified dynamic melting inversion (DMI) method presented her...
Theoretical studies of238U-230Th-226Ra and235U-231Pa disequilibria in young lavas produced by mantle melting
Geochimica et Cosmochimica Acta 64(10):1809 (2000)
This paper provides ready-to-use equations to describe variations in uranium-series (U-series) disequilibrium as a function of elemental distribution coefficients, melting porosity, melting rate, and melting time. The effects of these melting parameters on U-series disequilibria are quantit...
Exploring the kappa conundrum: the role of recycling in the lead isotope evolution of the mantle
Earth and Planetary Science Letters 169(1):129 (1999)
It has long been known that the measured kappa (
κ) of mid-ocean ridge basalts (MORB) and, by inference, the upper mantle, is much lower than the time-integrated
κ recorded by Pb isotope ratios (
Pb). We examine models that can reconci...
Mantle fluids: Evidence from fluid inclusions
Geochimica et Cosmochimica Acta 60(17):3229 (1996)
A total dissolution technique has been developed and used to identify and quantify the incompatible element contents of fluids trapped in inclusions in minerals from peridotite xenoliths using “fluids” in the generic sense (i.e., COH fluids and melts). Fluids from lherzolites, a wehr...
A major and trace element and strontium, neodymium, and osmium isotopic study of a thick pyroxenite layer from the Beni Bousera Ultramafic Complex of northern Morocco
Geochimica et Cosmochimica Acta 60(8):1429 (1996)
Major and trace element concentrations and strontium, neodymium, and osmium isotopic compositions were determined for a series of samples from a thick, symmetrically zoned pyroxenite layer from the Beni Bousera massif. The two main rock types included in the layer, garnet pyroxenites and we...
Constraints on the degree of dynamic partial melting and source composition using concentration ratios in magmas
Geochimica et Cosmochimica Acta 60(4):711 (1996)
We present a dynamic melting inversion (DMI) method that permits calculation of the degree of partial melting for cogenetic primary magmas in the context of the dynamic melting model of Langmuir et al. (1977). The method uses variations of between-magma concentration ratios for two incompat...
Distribution of dissolved and particulate230Th and232Th in seawater from the Gulf of Mexico and off Cape Hatteras as measured by SIMS
Earth and Planetary Science Letters 133(1):117 (1995)
We present vertical and horizontal profiles of dissolved and particulate
232Th concentrations in seawater from shelf and slope areas of the Gulf of Mexico and off Cape Hatteras in the Middle Atlantic Bight, as measured by secondary ion mass spectrometry (SIMS), and com...
Os isotope systematics of La Palma, Canary Islands: Evidence for recycled crust in the mantle source of HIMU ocean islands
Earth and Planetary Science Letters 133(3):397 (1995)
Sub-aerial lavas from the single ocean island of La Palma, Canary Islands show as large a variation in
isotope ratios (1.13–1.59) as found across all of French Polynesia ....
Extreme176Hf/177Hf in the sub-oceanic mantle
Earth and Planetary Science Letters 129(1):13 (1995)
The results of Hf isotopic analysis of peridotites are presented. Development of a hot-SIMS technique for Hf isotope analysis has made this possible at concentration levels that were previously prohibitively low.
177Hf ratios in abyssal peridotites and in two xenoliths f...
An isotopic study of the Ni-Cu-PGE-rich Wellgreen intrusion of the Wrangellia Terrane: Evidence for hydrothermal mobilization of rhenium and osmium
Geochimica et Cosmochimica Acta 58(2):1007 (1994)
Re-Os, Sm-Nd, Rb-Sr, and oxygen isotope systematics of the Wellgreen intrusion in the Wrangellia terrane were investigated in an effort to deduce the origin of this mafic-ultramafic sill and its attendant Ni-Cu-PGE deposit. Radiogenic initial Os ratios (1.06–1.82) and Sr ratios (0.7044–0.70...
Re-Os isotopic systematics in chromitites from the Stillwater Complex, Montana, USA
Geochimica et Cosmochimica Acta 57(16):4029 (1993)
New Re-Os isotopic data on chromitites of the Stillwater Complex demonstrate isotopic equilibrium between cumulate chromite and whole rock. Initial osmium isotopic ratios for the chromitites, chosen for their freshness, are consistent with derivation from a mantle-derived magma that suffere...
V. M. Goldschmidt Medal and Lester W. Strock and family honorarium:Introduction of Stanley R. Hart for the 1992 V. M. Goldschmidt award
Geochimica et Cosmochimica Acta 57(8):1891 (1993)
Os isotope systematics in ocean island basalts
Earth and Planetary Science Letters 120(3):149 (1993)
Os isotopic results for Os-poor basalts from St. Helena, the Comores, Samoa, Pitcairn and Kerguelen dramatically expand the known range of initial
187Os ratios in OIBs to values as high as 1.7. In contrast to the Os isotopic uniformity of Os-rich basalts fro...
Distribution and evolution of carbon and nitrogen in Earth
Earth and Planetary Science Letters 117(3):331 (1993)
In this paper we discuss the distribution, geochemical cycle, and evolution of CO
2 and N
2 in Earth's degassed mantle, and atmosphere plus continental crust. We estimate the present distribution of CO
2 and N
2 in Earth's degassed mantle based on amounts of He and A...
Uranium-234 anomalies in corals older than 150,000 years
Geochimica et Cosmochimica Acta 55(8):2385 (1991)
We present new precise U-Th ages of well-preserved coral specimens collected from the island of Barbados, West Indies, and the atoll of Mururoa, French Polynesia. Our new data confirm the ages attributed to oxygen isotope stage 7 in the framework of the Milankovitch theory (BERGER, 1978; Ma...
Further Sr and Nd isotopic results from peridotites of the Ronda Ultramafic Complex
Earth and Planetary Science Letters 96(1):161 (1989)
Clinopyroxenes derived from peridotites of the spinel and garnet facies of the Ronda Ultramafic Complex yield Sr and Nd isotopic ratios which extend the range of compositions found in the massif to values as depleted as 0.70205 for Sr and 0.51363 for Nd. Large-amplitude, short-wavelength is...