This volume contains the lectures presented at the NATO ADVANCED STUDY INSTITUTE that took place at Newark, Delaware, U.S.A., July 14-23, 1985. The objective of this meeting was to present and discuss selected topics associated with transport phenomena in porous media. By their very nature, porous media and phenomena of transport of extensive quantities that take place in them, are very complex. The solid matrix may be rigid, or deformable (elastically, or following some other constitutive relation), the void space may be occupied by one or more fluid phases. Each fluid phase may be composed of more than one component, with the various components capable of interacting among themselves and/or with the solid matrix. The transport process may be isothermal or non-isothermal, with or without phase changes. <...>

The geologic story of North America is a fascinating one. It’s also more than 4 billion years long—much more than we could ever hope to cover here. However, if you’re curious about the world around you, enjoy the big-picture perspective, and are interested in some of the processes that are constantly reshaping our planet, here’s a crash course on the basics. It’s a good place to start on your aerial tour of the continent’s most breathtaking landforms.

For many centuries Africa’s rich mineral endowment has shaped the fortunes of its peoples and the environment. Beginning in the early twenty-first century, the commodities price boom and concerns about human impacts on the environment have seen increasing value placed on the continent’s renewable and non-renewable natural resources. Operators explored and extracted mineral and energy resources at an unprecedented pace during the boom, with regulators scrambling to keep up. The limitations of the so-called commodities super cycle soon became apparent to Africa’s policymakers and investors alike, however, prompting a need for revised approaches to resource governance in the past five years.1 At the same time, competing land and water uses, deforestation, and loss of biodiversity remain key concerns for climate change mitigation and environmental conservation. This raises an enduring question: How does Africa develop its mineral fortune sustainably, both in environmental and in socio-economic terms? The concentration of low-income, resource-dependent countries in Africa places it at the center of global debates about sustainable development and the extractive industries. <...>

Carlin-type gold deposits are difficult to date and a wide range of ages has been reported for individual deposits. Therefore, several methods were employed to constrain the age of the gold deposits in the Jerritt Canyon district. Dated igneous rocks with well-documented crosscutting relationships to ore provided the most reliable constraints. K/Ar and 40Ar/39Ar dates on igneous rocks are as follows: andesite dikes 324 Ma, sericitic alteration in andesite dikes 118 Ma, basalt dikes 40.8 Ma, quartz monzonite dikes 39.2 Ma, and calc-alkaline ignimbrites 43.1 to 40.1 Ma. Of these, only the andesite and basalt dikes are clearly altered and mineralized. The gold deposits are, therefore, younger than the 40.8 Ma basalt dikes. The sericitic alteration in the andesite dikes is unrelated to the gold deposits. A number of dating techniques did not work. K/Ar and 40Ar/39Ar dates on mica from mineralized Ordovician to Devonian sedimentary rocks gave misleading results. The youngest date of 149 Ma from the smallest <0.1-)U,m-size fraction shows that the temperature (120°-260°C) and duration (?) of hydrothermal activity was insufficient to reset preexisting fine-grained micas in the host rocks. The temperature and duration was also insufficient to anneal fission tracks in zircon from Ordovician quartzites as they yield Middle Proterozoic dates in both mineralized and barren samples. Apatites were too small for fission track dating. Hydrothermal sulfides have pronounced crustal osmium isotope signatures (18'Os/188Osinitiai = 0.9-3.6) but did not yield a meaningful isochron due to very low Re and Os concentrations and large analytical uncertainties. Paleomagnetic dating techniques failed because the hydrothermal fluids sulfidized nearly all of the iron in the host rocks leaving no remnant magnetism.