STATE IMPLEMENTATION OF THE SURFACE MINING CONTROL AND RECLAMATION ACT OF 1977

The implementation of the Surface Mining Control and Reclamation Act (SMCRA) of 1977 in coal producing states is guided by a partial preemption policy approach t h a t establishes a balance between federal and state decision-making authority. The usefulness of this approach is assessed by analyzing state enforcement actions in relation the institutional capacity of states to shoulder regulatory responsibilities and the propensity of the federal Office of Surface Mining (OSM) t o oversee state enforcement actions and, if necessary, to undertake corrective action. Our results indicated that state administration of SMCRA was canstrained by the lack of effective federal oversight but was largely unaffected by interstate differences in political, economic, or administrative characteristics. Copyright 1989 by The Policy Studies Organization.

Petrology and Chemistry of Recent Lavas in the Northern Marianas: Implications for the Origin of Island Arc Basalts

Petrologic and chemical data are presented for samples from five volcanically active islands in the northern Marianas group, an intra-oceanic island arc. The data include microprobe analyses of phenocryst and xenolith assemblages, whole rock major and trace element chemistry including REE, and Sr isotope determinations (87Sr/86Sr=0.7034±0.0001). Quartz-normative basalt and basaltic andesite are the most abundant lava types. These are mineralogically and chemically similar to the mafic products of other intra-oceanic islands arcs. It is suggested, however, that they are not typical of the ‘island arc tholeiitic’ series, having Fe enrichment trends and K/Rb, for example, more typical of calc-alkaline suits. Major and trace element characteristics, and the presence of cumulate xenoliths, indicate that extensive near surface (\u3c 3 Kb) fractionation has occurred. Thus, even least fractionated basalts have low abundances of Mg, Ni and Cr, and high abundances of K and other large cation, imcompatible elements, relative to ocean ridge tholeiites. However, abundances of REE and small cation lithophile elements, such as Ti, Zr, Nb, and Hf are lower than typical ocean ridge tholeiites. The REE data and Sr isotope compositions suggest a purely mantle origin for the Marianas island arc basalts, with negligible input from subducted crustal material. Thus, subduction of oceanic lithosphere may not be a sufficient condition for initiation of island arc magmatism. Intersection of the Benioff zone with an asthenosphere under appropriate conditions may be requisite. Element ratios and abundances, combined with isotopic data, suggest that the source for the Marianas island arc basalts is more chondritic in some respects, and less depleted in large cations than the shallow (?) mantle source for ocean ridge tholeiites