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Harold Williams Series 318 HAROLD WILLIAMS SERIES widely separated regions experienced mately 500 m.y. of continental margin similar tectonomagmatic events, i.e., growth along southeastern Laurentia the Elzevirian (ca. 1.25–1.22 Ga), by accretion, continental margin arc Shawinigan (ca. 1.2–1.14 Ga), and magmatism, and metamorphism. Grenvillian (ca. 1.09–0.98 Ga) oroge- Accordingly, we briefly review the tec- nies and associated plate interactions. tonic and magmatic histories of these Notwithstanding these commonalities, Paleoproterozoic and Mesoproterozoic Nd model ages and Pb isotopic map- pre-Grenvillian orogens, i.e., Penokean, ping has revealed important differences Yavapai, and Mazatzal as well as the that are best explained by the existence Granite-Rhyolite Province and discuss of contrasting compositions of deep their ~5000 km transcontinental span. Tectonic Evolution of the crustal reservoirs beneath the Adiron- dacks and the southern Appalachians. SOMMAIRE Adirondack Mountains and The isotopic compositions for the Des recherches récentes en Grenville Orogen Inliers Adirondacks lie on the same Pb–Pb géochronologie et en tectonique révè- array as those for the Grenville lent d’importants faits nouveaux sur within the USA Province, the Granite-Rhyolite l’évolution de l’orogénie de Grenville en Amérique du Nord. Nous présen- Province and the Grenvillian inliers of 1 tons ici un sommaire des résultats de James M. McLelland , Bruce W. Texas suggesting that they all devel- 1 2 cet effort de recherche aux USA en Selleck , and Marion E. Bickford oped on Laurentian crust. On the mettant l’accent sur les indices datés other hand, data from the southern 1 entre env. 1,4 et 0,98 Ga, à partir des Department of Geology Appalachians are similar to those of Colgate University monts Adirondack jusqu’au sud des the Sunsas Terrane in Brazil and sug- Appalaches et au Texas. Des données Hamilton, NY, USA, 13346 gest that Amazonian crust with these Email: [email protected] géochronologiques récentes (par Pb–Pb characteristics was thrust onto microsonde SHRIMP principalement) eastern Laurentia during its Grenvillian indiquent que les roches de ces régions 2Department of Earth Sciences collision with Amazonia and subse- très éloignées les unes des autres ont Heroy Geology Laboratory quently transferred to the latter during subies l’effet d’épisodes tectonomag- Syracuse University the late Neoproterozoic breakup of matiques similaires, par exemple, aux Syracuse, NY, USA, 13244 the supercontinent, Rodinia, and the orogenèses de l’Elzévirien (env. formation of the Iapetus Ocean. The 1.25–1.22 Ga), de Shawinigan (env. SUMMARY ca. 1.3–1.0 Ga Grenville Orogen is also 1.2–1.14 Ga), et du Grenvillien (env. Recent investigations in geochronology exposed in the Llano Uplift of Texas 1.09–0.98 Ga), ainsi que des interac- and tectonics provide important new and in small inliers in west Texas and tions des plaques associées. Malgré ces insights into the evolution of the northeast Mexico. The Llano Uplift points communs, la chronologie Nd et Grenville Orogen in North America. contains evidence for a major collision la cartographie isotopique Pb a révélé Here, we summarize results of this with a southern continent at ca. des différences importantes qui s’ex- research in the USA and focus upon 1.15–1.12 Ga (Kalahari Craton?), mag- pliquent plus aisément par des compo- ca. 1.4–0.98 Ga occurrences extending matic arcs, and back-arc and foreland sitions contrastées des réservoirs pro- from the Adirondack Mountains to the basins, all of which are reviewed. fonds de croûte sous les Adirondacks southern Appalachians and Texas. The Grenvillian Orogeny is et le sud des Appalaches. Les compo- Recent geochronology (mainly by considered to be the culminating tec- sitions isotopiques des Adirondacks U/Pb SHRIMP) establishes that these tonic event that terminated approxi- sont de la même gamme Pb-Pb que Geoscience Canada, v. 40, http://dx.doi.org/10.12789/geocanj.2013.40.022 © 2013 GAC/AGC® GEOSCIENCE CANADA Volume 40 2013 319 ceux de la Province de Grenville, de la that evidence for many events of the Aleinikoff et al. (2004, 2008) and refer- Province Granite-rhyolite et des bou- same age are present in several loca- ences therein. At about the same time, tonnières grenvilliennes du Texas, sug- tions pointing to a shared tectonic evo- application of a range of other iso- gérant qu'ils se sont tous développées lution (McLelland et al. 2010a). Similar topic studies, e.g. Sm/Nd crustal dat- sur la croûte des Laurentides. Par timing of events is also noted between ing, oxygen isotopes, carbon isotopes, ailleurs, les données des Appalaches du the Adirondacks and the Mesoprotero- 40Ar/39Ar isotope geochemistry, Hf in sud sont semblables à celles du terrane zoic inliers of Texas. The shared evolu- zircon, and whole rock Pb/Pb investi- de Sunsas au Brésil, ce qui incite à tion of these terranes is summarized in gations greatly expanded the database, penser que la croûte amazonienne, this paper along with new develop- while modern geothermometry and avec de telles caractéristiques Pb-Pb, a ments of the past several years. geobarometry enabled a deeper under- été poussée sur la portion est de Lau- Isotope geochemistry and standing of processes and events rentia lors de sa collision grenvillienne geochronology have played major roles involved in the evolution of the avec l’Amazonie puis laissée à cette in extending our understanding of the Adirondacks as well as the Grenvillian dernière au cours de la rupture du entire Grenville Orogen, including the inliers of the Appalachians and Texas. supercontinent Rodinia vers la fin du Adirondacks where they have clarified References to these studies, together Néoprotérozoïque, avec la formation a geological history that had remained with appropriate citations, are made in de l'océan Iapetus. L’orogène de obscure for decades. The earliest sys- the text itself. Prior to this, we briefly Grenville (1,3 à 1,0 Ga env.) est égale- tematic U–Pb zircon dating studies summarize the pre-Grenvillian Pro- ment exposé dans le soulèvement de were due to L.T. Silver (Silver 1969) terozoic history of a long-lived series Llano au Texas et dans de petites bou- who used the Adirondacks as a labora- of continental margin arcs along tonnières dans l'ouest du Texas et le tory in which to advance his pioneer- southeastern Laurentia, i.e., the Paleo- nord du Mexique. Le soulèvement de ing research in multi-grain U–Pb zir- proterozoic Penokean, Yavapai, and Llano montre des indices d'une colli- con dating. Subsequent multi-grain Mazatzal orogens, together with the sion majeure avec un continent au sud, U–Pb zircon dating by McLelland et al. Mesoproterozoic Granite-Rhyolite entre env. 1,15 et 1,12 Ga (craton de (1988) and McLelland and Chiarenzelli Province. Tectonomagmatic activity Kalahari?), des zones d’arcs magma- (1990) extended Silver’s results and, for along these arcs set the stage for the tiques, d'arrière-arc et de bassin d'a- the first time, established a coherent culminating Grenvillian Orogeny that vant-pays, chacun étant présenté ci- chronology and sequence of events in resulted in the creation of the Rodin- dessous. the Adirondack Mountains. The results ian supercontinent. L'orogenèse de Grenville est demonstrated that the region was considéré comme l'événement tec- affected by three major orogenic REGIONAL SETTING OF THE tonique culminant qui marqué la fin events: the Elzevirian Orogeny GRENVILLE OROGEN WITHIN THE d’une période d’environ 500 ma d’ac- (1.25–1.22 Ga), the Shawinigan Oroge- USA croissement de la marge continentale le ny (ca. 1.16–1.14 Ga), and the Ottawan The Grenville Orogen (Fig. 1) repre- long de la bordure sud-est de la Lau- Orogeny (ca. 1.09–1.03 Ga) as well as sents the youngest of a series of Pale- rentie, par accrétion, magmatisme d’arc the late- to post-orogenic anorthosite– oproterozoic to Mesoproterozoic de marge continentale, et métamor- mangerite–charnockite–granite crustal additions to the southeastern phisme. C’est pourquoi, nous passons (AMCG) suite at ca. 1.15 Ga. This Laurentian margin. From oldest to brièvement en revue l'histoire tec- framework provided boundary condi- youngest, on the basis of Nd model tonique et magmatique de ces orogènes tions enabling the unraveling of ages (TDM), these include: the Penokean pré-grenvilliennes paléoprotérozoïques Adirondack tectonomagmatic history (ca. 2.0–1.8 Ga), Yavapai (ca. 1.8–1.7 et mésoprotérozoïques, pénokéenne, and placing the region into a self-con- Ga), and Mazatzal (ca. 1.87–1.65 Ga) de Yavapai, et de Mazatzal ainsi que la sistent plate tectonic overview that we provinces or orogens, and the Granite- Province de Granite-rhyolite, et discu- present here. More recently, McLelland Rhyolite Province (ca. 1.487–1.37 Ga). tons de son étendue sur env. 5 000 km. and co-workers (McLelland et al. 2001, Together, these terranes have been 2002, 2004; Heumann et al. 2006; Bick- interpreted as long-lived island and INTRODUCTION ford et al. 2010; Chiarenzelli et al. continental margin arcs that were the The Adirondack Mountains constitute 2010, 2011) undertook the first dating site of accretion and juvenile pluton- the southernmost contiguous portion of Adirondack zircon by U–Pb ism that resulted in ~600 million years of the Mesoproterozoic Grenville SHRIMP2 techniques and this has of crustal additions to Laurentia and Province (Fig. 1) and, as such, are well vastly improved understanding of the culminated with the 1.3–0.98 Ga Elze- situated to make geologic connections detailed geochronology of events in virian, Shawinigan and Grenvillian oro- with Grenvillian inliers in the the region. Both SHRIMP2 and ther- genies (Karlstrom et al. 2001; Whit- Appalachian Mountains to the south- mal ionization mass spectrometry meyer and Karlstrom 2007, and refer- east and with those in the Midconti- (TIMS) ages are presented in Table 1 ences therein).
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