POLLUTION AND PRESERVATION
By James I. Drever | December, 2012
The topic of urban geochemistry brings up the whole issue of the livability of cities and in particular the adaptation of historic cities to modern ways of living. Old towns and cities present problems for modern lifestyles. In addition to the problems of pollution discussed in this issue, there are fundamental questions concerning the adaptation of old cities to today’s lifestyles—I’m thinking of motor vehicles as well as the basics of electricity and plumbing. What value do we place on the preservation of old buildings? This question has had different answers at different times. After the Second World War, urban planners in Britain saw the bomb damage as a glorious opportunity to sweep away the impractical old buildings and erect modern city centers of concrete and glass. In Germany, on the other hand, much more emphasis was given to preservation of what had survived and rebuilding of what had not. Attitudes today in most countries favor preservation, but ideas as to what is worth preserving differ widely.
TAL ES, TALES…
By Georges Calas | October, 2012
The formation of ore deposits often appears to result from a “magic chain” made from a coherent succession of geological, geochemical, mineralogical, etc. processes that concentrate metallic elements. The efficiency of such element concentration is really extraordinary, as illustrated by elements such as gold, which is concentrated from the ppb level to nuggets weighing 70 kg. As a consequence, humankind has used for millennia these mineral resources, which have been central to technological progress since the Stone Age. And it is still the case. Rare earth elements do not take full advantage of this “magic chain.” The most abundant rare earth elements are indeed similar in crustal abundance to transition elements such as chromium or nickel. Despite this, ore deposits of the former are much rarer than those of the latter.
MIGMA VERSUS MA GMA
By John W. Valley | August, 2012
Much has been written about the great Granitization Controversy of the mid-twentieth century and of the Neptunist– Magmatist conflict, 150 years earlier. In one, granites were proposed to be metamorphic rocks and in the other, sedimentary. The idea that most granites formed without melting seems strange today, but it held great sway among geologists for over 100 years. In truth, evidence abounds in high grade metamorphic terrains for small-scale granitization. Granitizers went further, however, and asserted that entire granitic plutons form in this manner and that they could not be intrusive because of “the room problem.” Related controversies questioned the genesis of migmatites, anorthosites, granulites, and mafic fronts, to name but a few. There are current analogies in the study of pegmatites, as this issue of Elements describes.
BREAKING BOUNDARIES
By Georges Calas | June, 2012
Fifteen months have passed since a gigantic earthquake and resulting tsunami hit the Japanese islands on March 11, 2011, resulting in some 20,000 people killed or missing. Subsequent flooding of the Fukushima Daiichi nuclear power plant led to a major crisis, with radioactive contamination developing in the ensuing days and creating public fear and confusion. As observed in many countries, this accident may have superseded concerns of how Japan had been severely affected by the megatsunami and, to a lesser extent, the earthquake of March 11.
DECISIONS DECISIONS
By Tim Drever | April, 2012
In a previous editorial (Elements, December 2011), I discussed how difficult it is to predict with certainty the environmental impact of activities such as mining, energy production, and radioactive waste disposal. Here I shall continue on this theme with some musings on how regulatory decisions are made—particularly in the United States, the country with which I am most familiar. The first obvious point is that any activity such as mining or energy production will have an impact on the environment. Generally speaking the impact will be negative— loss of wildlife habitat, visual disturbance, air and water pollution. On the other hand there are benefits to society—we need energy and we need mineral resources. Ideally, conservation, substitution, and recycling will reduce these requirements, but they will not be eliminated, at least in the short term.
LIVING IN THE FAST LINE
By Hap McSween | February, 2012
We spend our days on a world that is constantly battered by foreign objects (“bolides”) traveling at very high speeds. The consequences of bolide impacts are described in this issue of Elements. Before bolides encounter our planet, they are called near-Earth objects (NE Os) , denoting asteroids or comets whose orbits approach the Earth’s orbit and so are potentially capable of striking us with devastating effect.