Russell S. Harmon

Bio: Russell S. Harmon is an academic researcher from North Carolina State University. The author has contributed to research in topics: Laser-induced breakdown spectroscopy & Basalt. The author has an hindex of 62, co-authored 259 publications receiving 12597 citations. Previous affiliations of Russell S. Harmon include Michigan State University & United States Army Corps of Engineers.

The hydrology of the humid tropics

Abstract: Hydrological processes in the humid tropics differ from other regions in having greater energy inputs and faster rates of change. In this Review it is argued that understanding of the key hydrological interactions there remains limited, and a vision of future research designed to address these shortcomings is outlined.

Oxygen isotope heterogeneity of the mantle deduced from global 18 O systematics of basalts from different geotectonic settings

Abstract: Based upon a compilation and analysis of O-isotope data for Neogene volcanic rocks worldwide, the δ18O variation for 743 basalts (historic lavas, submarine glasses, and lavas with <0.75 wt% H2O) is +2.9 to +11.4‰. Mid-ocean-ridge basalt (MORB) has a uniform O-isotope composition with δ180=+5.7±0.2‰. Basalts erupted in different tectonic settings have mean 18O/16O ratios that are both lower and higher than MORB, with continental basalts enriched in 18O by ca. 1‰ over oceanic basalts. The δ18O range for the subset of 88 basalts with Mg# [100·Mg(Mg+Fe2+)] 75–68, considered to be unmodified primary mantle partial melts, is +3.6 to +8.7‰. These features are a clear indication that: (1) the Earth's upper mantle is heterogeneous with respect to its O-isotope composition; (2) that both low-18O and high-18O reservoirs have contributed to basalt petrogenesis. Large-ion lithophile element-enriched basalts associated with subduction at convergent plate margins are slightly enriched in 18O, a characteristic that is considered to be an intrinsic feature of the subduction process. Intraplate oceanic and continental basalts have highly variable 18O/16O ratios, with individual localities displaying δ18O ranges in excess of 1.5 to 2‰. Systematic co-variations between O-, Sr-, Nd-, and Pb-isotope ratios reflect the same principal intramantle end-member isotopic components (DMM, HIMU, EM-I, EM-II) deduced from radiogenic isotope considerations and, therefore, imply that a common process is responsible for the origin of upper mantle stable and radiogenic isotope heterogeneity, namely the recycling of lithospheric material into the mantle.

Chemical and isotopic systematics of oceanic basalt : implications for mantle composition and processes

Abstract: Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.

Pattern Recognition and Machine Learning

Abstract: Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Composition of the Continental Crust

Abstract: This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories. We review the composition of the upper, middle, and lower continental crust. We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes. Finally, we compare the Earth's crust with those of the other terrestrial planets in our solar system and speculate about what unique processes on Earth have given rise to this unusual crustal distribution.

The geochemical evolution of the continental crust

Abstract: A survey is given of the dimensions and composition of the present continental crust. The abundances of immobile elements in sedimentary rocks are used to establish upper crustal composition. The present upper crustal composition is attributed largely to intracrustal differentiation resulting in the production of granites senso lato. Underplating of the crust by ponded basaltic magmas is probably a major source of heat for intracrustal differentiation. The contrast between the present upper crustal composition and that of the Archean upper crust is emphasized. The nature of the lower crust is examined in the light of evidence from granulites and xenoliths of lower crustal origin. It appears that the protoliths of most granulite facies exposures are more representative of upper or middle crust and that the lower crust has a much more basic composition than the exposed upper crust. There is growing consensus that the crust grows episodically, and it is concluded that at least 60% of the crust was emplaced by the late Archean (ca. 2.7 eons, or 2.7 Ga). There appears to be a relationship between episodes of continental growth and differentiation and supercontinental cycles, probably dating back at least to the late Archean. However, such cycles do not explain the contrast in crustal compositions between Archean and post-Archean. Mechanisms for deriving the crust from the mantle are considered, including the role of present-day plate tectonics and subduction zones. It is concluded that a somewhat different tectonic regime operated in the Archean and was responsible for the growth of much of the continental crust. Archean tonalites and trond-hjemites may have resulted from slab melting and/or from melting of the Archean mantle wedge but at low pressures and high temperatures analogous to modern boninites. In contrast, most andesites and subduction-related rocks, now the main contributors to crustal growth, are derived ultimately from the mantle wedge above subduction zones. The cause of the contrast between the processes responsible for Archean and post-Archean crustal growth is attributed to faster subduction of younger, hotter oceanic crust in the Archean (ultimately due to higher heat flow) compared with subduction of older, cooler oceanic crust in more recent times. A brief survey of the causes of continental breakup reveals that neither plume nor lithospheric stretching is a totally satisfactory explanation. Speculations are presented about crustal development before 4000 m.y. ago. The terrestrial continental crust appears to be unique compared with crusts on other planets and satellites in the solar system, ultimately a consequence of the abundant free water on the Earth.