Isotopic tracers of gold deposition in Paleozoic limestones, Southern Nevada

Strontium isotopic analyses of barren and mineralized Paleozoic carbonate rocks show that hydrothermal fluids added radiogenic strontium ({sup 87}Sr) to the mineralized zones. At Bare Mountain, samples collected from mineralized areas have {delta}{sup 87}Sr{sub t} values ranging from +3.0 to +23.0, whereas unmineralized carbonate rocks have {delta}{sup 87}Sr, values of {minus}0.6 to +2.9. In other ranges, {delta}{sup 87}Sr, values of the unmineralized carbonate rocks are even lower and virtually indistinguishable from primary marine values. This correlation of elevated {delta}{sup 87}Sr{sub t} values with mineralized zones provides a useful technique for assessing the mineral potential of the Paleozoic basement beneath Yucca Mountain, and may find broader use in mineral exploration in the Basin and Range province as a whole

Neoproterozoic to early Paleozoic extensional and compressional history of East Laurentian margin sequences: The Moine Supergroup, Scottish Caledonides

Neoproterozoic siliciclastic-dominated sequences are widespread along the eastern margin of Laurentia and are related to rifting associated with the breakout of Laurentia from the supercontinent Rodinia. Detrital zircons from the Moine Supergroup, NW Scotland, yield Archean to early Neoproterozoic U-Pb ages, consistent with derivation from the Grenville-Sveconorwegian orogen and environs and accumulation post–1000 Ma. U-Pb zircon ages for felsic and associated mafic intrusions confirm a widespread pulse of extension-related magmatism at around 870 Ma. Pegmatites yielding U-Pb zircon ages between 830 Ma and 745 Ma constrain a series of deformation and metamorphic pulses related to Knoydartian orogenesis of the host Moinerocks. Additional U-Pb zircon and monazite data, and 40Ar/39Ar ages for pegmatites and host gneisses indicate high-grade metamorphic events at ca. 458–446 Ma and ca. 426 Maduring the Caledonian orogenic cycle.The presence of early Neoproterozoic silici clastic sedimentation and deformation in the Moine and equivalent successions around the North Atlantic and their absence along strike in eastern North America reflect contrasting Laurentian paleogeography during the breakup of Rodinia. The North Atlantic realm occupied an external location on the margin of Laurentia, and this region acted as a locus for accumulation of detritus (Moine Supergroup and equivalents) derived from the Grenville-Sveconorwegian orogenic welt, which developed as a consequence of collisional assembly of Rodinia. Neoproterozoic orogenic activity corresponds with theinferred development of convergent platemargin activity along the periphery of the supercontinent. In contrast in eastern North America, which lay within the internal parts of Rodinia, sedimentation did not commence until the mid-Neoproterozoic (ca. 760 Ma) during initial stages of supercontinent fragmentation. In the North Atlantic region, this time frame corresponds to a second pulse of extension represented by units such as the Dalradian Supergroup, which unconformably overlies the predeformed Moine succession

The Influence of International Law on the International Movement of Persons

Many migration theories identify ‘the law’ as a significant constraint on the international movement of persons. While this constraint often operates through national migration legislation, this study examines the influence of international law in shaping contemporary patterns in the international movement of persons at the macro level. The analysis begins with an examination of the long-established power of a State to regulate cross-border movement of persons as an inherent attribute of State sovereignty, together with the accepted limitations on a State’s power to control entry and exit. Yet, international law reaches well beyond the movement of people across borders. The development of international human rights law has been a key constraint on state action in the United Nations era by also regulating the treatment of migrants within a State’s borders. The study considers how international law has responded to current migration issues, including: protection of migrant women and children; suppression of smuggling and trafficking of people; labour migration; and environmental migration. As in other areas of international society, there has been a proliferation of institutions through which international migration law is made and enforced. The most prominent among them are the United Nations High Commissioner for Refugees (UNHCR) and the International Organization for Migration (IOM), but the establishment of other entities with overlapping mandates has given rise to calls for a new international migration regime based on streamlined institutional arrangements. The study concludes that international law is an imperfect framework for regulating the international movement of persons because it has developed in a piecemeal fashion over a long time to deal with issues of concern at particular points in human history. Yet, despite its shortfalls, international law and its associated institutions unquestionably play a most important role in constraining and channeling state authority over the international movement of persons

Model International Mobility Convention

While people are as mobile as they ever were in our globalized world, the movement of people across borders lacks global regulation. This leaves many refugees in protracted displacement and many migrants unprotected in irregular and dire situations. Meanwhile, some states have become concerned that their borders have become irrelevant. International mobility—the movement of individuals across borders for any length of time as visitors, students, tourists, labor migrants, entrepreneurs, long-term residents, asylum seekers, or refugees—has no common definition or legal framework. To address this key gap in international law, and the growing gaps in protection and responsibility that are leaving people vulnerable, the "Model International Mobility Convention" proposes a framework for mobility with the goals of reaffirming the existing rights afforded to mobile people (and the corresponding rights and responsibilities of states) as well as expanding those basic rights where warranted. In 213 articles divided over eight chapters, the Convention establishes both the minimum rights afforded to all people who cross state borders as visitors, and the special rights afforded to tourists, students, migrant workers, investors and residents, forced migrants, refugees, migrant victims of trafficking and migrants caught in countries in crisis. Some of these categories are covered by existing international legal regimes. However, in this Convention these groups are for the first time brought together under a single framework. An essential feature of the Convention is that it is cumulative. This means, for the most part, that the chapters build on and add rights to the set of rights afforded to categories of migrants covered by earlier chapters. The Convention contains not only provisions that afford rights to migrants and, to a lesser extent, States (such as the right to decide who can enter and remain in their territory). It also articulates the responsibilities of migrants vis-à-vis States and the rights and responsibilities of different institutions that do not directly respond to a right held by migrants

Nationality and migration in modern Mexico

Scholarship on nationalism and the state has examined how immigration and nationality policy create boundaries of inclusion and exclusion. While a handful of countries of immigration have been analysed extensively, explanations of nationality law have not accounted adequately for countries of emigration. This paper's historical analysis of Mexican nationality law and its congressional debate demonstrates that the ways the state has defined nationality at different periods cannot be attributed simply to demographic migration patterns or legacies of past understandings of ethnic or state-territorial nationhood, according to the expectations of received theory. The literature's focus on geopolitically stronger countries of immigration obscures the critical effects of inter-state politics on nationality law in subordinate states. Mexico's nationality laws reflect its experiences as a geopolitically weak country of immigration, despite a net out-migration of its population