SILURIAN AND EARLY DEVONIAN AGES FOR THE MIXER POND AND ASSOCIATED ORTHOGNEISS PROVIDE AGE CONSTRAINTS ON MAGMATIC ACTIVITY, MIGMATIZATION, AND DEXTRAL SHEAR EVENTS IN THE LIBERTY–ORRINGTON BELT OF SOUTH–CENTRAL MAINE

2017 ◽  
Author(s):  
Stephen G. Pollock ◽  
◽  
K. Gray ◽  
David Gibson ◽  
Jeffrey Vervoort
Keyword(s):  
Magmatic Activity ◽  
Early Devonian ◽  
South Central ◽  
Dextral Shear ◽  
Age Constraints

scholarly journals Granitoid plutons in peri-Gondwanaan terranes of Cape Breton Island, Nova Scotia, Canada: new U-Pb (zircon) age constraints

2018 ◽  
pp. 021-080 ◽  
Author(s):  
Sandra M. Barr ◽  
Deanne Van Rooyen ◽  
Chris E. White
Keyword(s):  
Tectonic Setting ◽  
Magmatic Activity ◽  
Zircon Age ◽  
Cape Breton Island ◽  
The Past ◽  
Late Cambrian ◽  
Cape Breton ◽  
History Of ◽  
Tectonic Settings ◽  
Age Constraints

Granitoid plutons are a major component of pre-Carboniferous rocks in Cape Breton Island and knowledge of the time and tectonic setting of their emplacement is crucial for understanding the geological history of the island, guiding exploration for granite-related economic mineralization, and making along-orogen correlations. The distribution of these plutons and their petrological characteristics have been used in the past for recognizing both Laurentian and peri-Gondwanan components in Cape Breton Island, and for subdividing the peri-Gondwanan components into Ganderian and Avalonian terranes. However, ages of many plutons were assumed on the basis of field relations and petrological features compared to those of the relatively few reliably dated plutons. Seventeen new U–Pb (zircon) ages from igneous units reported here provide enhanced understanding of the distribution of pluton ages. Arc-related plutons in the Aspy terrane with ages of ca. 490 to 475 Ma likely record the Penobscottian tectonomagmatic event recognized in the Exploits subzone of central Newfoundland and New Brunswick but not previously recognized in Cape Breton Island. Arc-related Devonian plutonic activity in the same terrane is more widespread, continuous, and protracted (445 Ma to 395 Ma) than previously known. Late Devonian magmatism in the Ganderian Aspy terrane is similar in age to that in the Avalonian Mira terrane (380 to 360 Ma) but the tectonic settings are different. In contrast, magmatic activity in the Bras d’Or terrane is almost exclusively arc-related in the Late Ediacaran (580 to 540 Ma) and rift-related in the Late Cambrian (520 to 490 Ma). The new data support the terrane distinctions previously documented.

scholarly journals Geochronology of plutonic rocks from the Sanandaj-Sirjan zone, Iran and new zircon and titanite U-Th-Pb ages for granitoids from the Marivan pluton

2014 ◽  
Vol 41 (3) ◽  
pp. 207-215 ◽  
Author(s):  
Ali Sepahi ◽  
Hossein Shahbazi ◽  
Wolfgang Siebel ◽  
Ahmad Ranin
Keyword(s):  
Continental Margin ◽  
Late Jurassic ◽  
Active Continental Margin ◽  
Continental Collision ◽  
Magmatic Activity ◽  
Geochronological Data ◽  
Metamorphic Belt ◽  
Sanandaj Sirjan Zone ◽  
Orogenic Cycle ◽  
Age Constraints

Abstract The Sanandaj-Sirjan zone of Iran is a metamorphic belt consisting of rocks which were metamorphosed under different pressure and temperature conditions and intruded by various plutons ranging in composition from gabbro to granite. The majority of these granitoids formed along the ancient active continental margin of the Neo-Tethyan ocean at the southeastern edge of the central Iranian microplate. Geochronological data published in recent years indicate periodic plutonism lasting from Carboniferous through Mesozoic to late-Paleogene times (from ca. 300 to ca. 35 Ma) with climax activity during the mid- and late-Jurassic. The age constraints for plutonic complexes, such as Siah-Kouh, Kolah-Ghazi, Golpayegan (Muteh), Azna, Aligoodarz, Astaneh, Borujerd, Malayer (Samen), Alvand, Almogholagh, Ghorveh, Saqqez, Marivan, Naqadeh and Urumieh, clearly indicate the periodic nature of magmatism. Therefore, the Sanandaj-Sirjan zone preserves the record of magmatic activity of a complete orogenic cycle related to (1) Permocarboniferous(?) rifting of Gondwana and opening of the Neo-Tethyan ocean, (2) subduction of the oceanic crust, (3) continental collision and (4) post-collision/post-orogenic activities. The formation of the Marivan granitoids, northwestern Sanandaj-Sirjan zone, for which we present U-Pb zircon and titanite ages of ca. 38 Ma, can be related to the collisional and post-collisional stages of this orogenic cycle.

scholarly journals Direct dating of lithic surface artifacts using luminescence

2021 ◽  
Vol 7 (23) ◽  
pp. eabb3424
Author(s):  
Luke Andrew Gliganic ◽  
Michael Christian Meyer ◽  
Jan-Hendrik May ◽  
Mark Steven Aldenderfer ◽  
Peter Tropper
Keyword(s):  
Optically Stimulated Luminescence ◽  
Rock Surface ◽  
Earth Surface ◽  
Surface Dynamics ◽  
Dynamic Nature ◽  
South Central ◽  
Central Tibetan Plateau ◽  
Human Use ◽  
Surface Scatter ◽  
Age Constraints

Archaeological surface assemblages composed of lithic scatters comprise a large proportion of the archaeological record. Dating such surface artifacts has remained inherently difficult owing to the dynamic nature of Earth-surface processes affecting these assemblages and because no satisfactory chronometric dating technique exists that can be directly applied to constrain the timing of artifact manufacture, discard, and thus human use of the landscape. Here, we present a dating approach based on optically stimulated luminescence (OSL)—OSL rock-surface burial dating—and apply it to a lithic surface scatter in Tibet. We generate OSL burial ages (age-depth profiles) for each artifact, outline the methodological complexities, and consider the artifact burial ages in the context of local-scale Earth-surface dynamics. The oldest age cluster between 5.2 and 5.5 thousand years is likely related to quarrying activities at the site and thus represents the oldest chronometric age constraints for human presence on the south-central Tibetan plateau.

Field Excursions from the 2021 GSA Section Meetings

2021 ◽  
Keyword(s):  
Barrier Islands ◽  
Shear Zones ◽  
The United States ◽  
High Energy ◽  
North Central ◽  
Field Guides ◽  
South Central ◽  
Geologic Map ◽  
Dextral Shear ◽  
Central South

The 2021 GSA Northeastern, Southeastern, joint North-Central/South-Central, and Cordilleran Section Meet-ings were held virtually in spring 2021 during continued restrictions on travel and large gatherings due to COVID-19. Eleven groups put together field guides, taking participants on treks to states from Connecticut to Nevada in the United States, to Mexico, and to Italy, and covering topics as varied as bedrock geologic map-ping, geochemistry, paleodrainage, barrier islands, karst, spring systems, a southern Appalachian transect, Ordo-vician and Mississippian stratigraphy, high-energy events, Cretaceous arc granites and dextral shear zones, and Mesoproterozoic igneous rocks. This volume serves as a valuable resource for those wishing to discover, learn more about, and travel through these geologically fascinating areas.

scholarly journals Zircon age constraints on the provenance of Llandovery to Wenlock sandstones from the Midland Valley terrane of the Scottish Caledonides

2009 ◽  
Vol 45 (2) ◽  
pp. 131-146 ◽  
Author(s):  
E. R. Phillips ◽  
R. A. Smith ◽  
P. Stone ◽  
V. Pashley ◽  
M. Horstwood
Keyword(s):  
Detrital Zircon ◽  
Sedimentary Rocks ◽  
Sedimentary Facies ◽  
Volcanic Arc ◽  
Zircon Age ◽  
Early Devonian ◽  
Southern Side ◽  
Lower Palaeozoic ◽  
Metamorphic Terrane ◽  
Age Constraints

SynopsisDetrital zircon populations within the Llandovery to Wenlock sandstones of the southern Midland Valley of Scotland indicate that the recycled orogenic provenance for these sedimentary rocks was essentially bimodal, comprising a younger Lower Palaeozoic component and an older predominantly Mesoproterozoic component. The Lower Palaeozoic contribution is dominated by Arenig/Llanvirn (c. 475 Ma) zircons interpreted as having been derived from a volcanic-plutonic source located within the Midland Valley terrane. The dominant Mesoproterozoic component within the sandstones is c. 1000 Ma and is thought to represent detritus shed from a Grenvillian (c. 1000–1800Ma) basement to the Midland Valley terrane. The scarcity of Archaean zircons precludes the Grampian metamorphic terrane Dalradian Supergroup as a supplier of sediment to the Ordovician–Silurian basins located along the southern margin of the Midland Valley. The age profiles of detrital zircon populations do not fit with a simple model of unroofing of a volcanic-arc complex. Rather they point to the periodic uplift of fault-bound, dismembered blocks of volcanic and plutonic rocks during a prolonged (Llandovery through to at least early Devonian) period of sinistral strike-slip deformation, and it was this which controlled basin development, sedimentary facies distribution and deformation along the southern side of the Midland Valley terrane.Appendices 1 & 2 can be found at http://www.geolsoc.org.uk/SUP18370

U – Pb age constraints for the lithotectonic evolution of the Grenville Province along the Mauricie transect, Quebec

1997 ◽  
Vol 34 (3) ◽  
pp. 299-316 ◽  
Author(s):  
David Corrigan ◽  
Otto van Breemen
Keyword(s):  
Shear Zone ◽  
Tectonic Evolution ◽  
High Grade ◽  
Isotopic Age ◽  
Grenville Province ◽  
Zircon Age ◽  
South Central ◽  
Continental Arc ◽  
Structural Levels ◽  
Age Constraints

New U–Pb zircon and monazite ages on 12 samples from the Mauricie transect in Quebec provide constraints on the lithologic and tectonic evolution of the south-central Grenville Province. From lowest to highest structural levels, the Mékinac, Shawinigan, and Portneuf – St. Maurice domains are identified on the basis of protolith age, tectonic overprint, and plutonism. The structurally highest Portneuf – St. Maurice domain consists of remnants of an island arc (Montauban Group) that was deformed and metamorphosed before and during the intrusion of continental arc plutons (La Bostonnais complex). A tonalitic orthogneiss yielding a [Formula: see text] zircon age suggests that most of the structurally underlying Mékinac and Shawinigan domains consist of orthogneisses that may be high-grade equivalents of the La Bostonnais complex. A voluminous metasedimentary unit occurring in the Shawinigan domain (St. Boniface unit) was deposited between ca. 1.18 and 1.09 Ga, precluding any correlation with the ca. 1.45 Ga Montauban Group. Two suites of anorthosite–mangerite–charnockite–granite (AMCG) plutonic rocks are identified on the basis of field relationships and isotopic age. A megacrystic granite belonging to the "older" AMCG suite yielded a [Formula: see text] zircon age. Three plutons from the "younger" suite yielded ages of [Formula: see text], 1059 ± 2, and 1056 ± 2 Ma. The Mékinac and Shawinigan domains, excluding the younger AMCG plutons, were penetratively deformed at granulite to uppermost amphibolite facies during west-northwest-directed thrusting between 1.15 and 1.09 Ga. At ca. 1.09 Ga, a transition from contraction to oblique extension resulted in the juxtaposition of the "cold" Portneuf – St. Maurice domain with the "hot" Shawinigan domain, along the Tawachiche shear zone. Oblique extension may have been active from ca. 1.09 to 1.04 Ga and was contemporaneous with emplacement of the younger AMCG suite.

LA-ICP-MS U–Pb zircon, columbite-tantalite and40Ar–39Ar muscovite age constraints for the rare-element pegmatite dykes in the Altai orogenic belt, NW China

2016 ◽  
Vol 155 (3) ◽  
pp. 707-728 ◽  
Author(s):  
QIFENG ZHOU ◽  
KEZHANG QIN ◽  
DONGMEI TANG ◽  
CHUNLONG WANG ◽  
PATRICK ASAMOAH SAKYI
Keyword(s):  
Late Jurassic ◽  
Middle Triassic ◽  
Temporal Distribution ◽  
Middle Permian ◽  
Magmatic Activity ◽  
Weighted Mean ◽  
Rare Element ◽  
Nw China ◽  
Icp Ms ◽  
Age Constraints

AbstractThe Chinese Altai is renowned for its rich rare-element resources. Nine representative rare-element (REL) pegmatites were dated using LA-ICP-MS and40Ar–39Ar methods. The columbite grains yield a weighted mean206Pb/238U age of 239.6±3.8 Ma for the Dakalasu (Be-Nb-Ta) pegmatite and concordia U–Pb ages of 258.1±3.1 Ma and 262.3±2.5 Ma for the Xiaokalasu (Li-Nb-Ta) pegmatite. The zircons display a weighted mean206Pb/238U age of 198.5±2.5 Ma for the Husite (Be) pegmatite and concordia U–Pb ages of 194.3±1.6 Ma and 248.2±2.2 Ma for the Qunkuer (Be) and Taerlang (barren) pegmatites. The muscovite40Ar–39Ar dating gives plateau ages of 286.4±1.6 Ma, 297.0±2.6 Ma, 265.2±1.5 Ma, 178.8±1.0 Ma, 162.2±0.9 Ma, 237.7±1.3 Ma, 237.4±1.2 Ma and 231.9±1.2 Ma for the Talate (Li-Be-Nb-Ta), Baicheng (Nb-Ta), Kangmunagong (barren), Husite (Be), Qunkuer (Be-Nb-Ta), Xiaokalasu (Li-Nb-Ta), Weizigou (Be) and Taerlang (barren) pegmatites, respectively. These new ages coupled with previous geochronological work suggest that the REL pegmatites in the Chinese Altai formed during early Permain – Late Jurassic time. The REL pegmatites located in the Central Altaishan terrane are younger than those in the Qiongkuer–Abagong terrane, showing a correlation with the coeval and adjacent granites. The formation of the REL pegmatites and these granites indicates frequent and strong magmatic activity in the post-orogenic and anorogenic setting. The spatial and temporal distribution of pegmatites and granites reveals a magmatism path from the SE (of age early–middle Permian), to the NW (middle Permian – Middle Triassic) and finally to the central part (Middle Triassic – Jurassic) of the Chinese Altai.

The Red Island Road Formation: Early Devonian terrestrial fill in the Anticosti Foreland Basin, western Newfoundland

2004 ◽  
Vol 41 (5) ◽  
pp. 587-602 ◽  
Author(s):  
L Quinn ◽  
A R Bashforth ◽  
E T Burden ◽  
H Gillespie ◽  
R K Springer ◽  
...  
Keyword(s):  
Foreland Basin ◽  
Low Grade ◽  
Early Devonian ◽  
Plant Remains ◽  
Assemblage Zone ◽  
Metamorphic Terrane ◽  
Characteristic Features ◽  
Age Constraints ◽  
Radical Shift ◽  
Early Late

More than 100 m of nearly flat-lying, fluvially derived, thick-bedded and lensoid, clast-supported conglomerate and sandstone are found on Red Island, off the coast of the Port au Port Peninsula, western Newfoundland. Formally described herein and named Red Island Road Formation, the strata represent a unique lithologic formation not exposed or known anywhere else in the region. Characteristic features include abundant, rounded, highly weathered and varnished cobbles and boulders derived from an unknown mixed volcanic and very low to low-grade metamorphic terrane. Although the unit is largely unfossiliferous, a thin sandstone bed near the top of the type section contains primitive dichotomously branched plant remains and biostratigraphically significant palynomorphs. Among more than 25 species of spores, it is the diversity of Emphanisporites, Dictyotriletes, and Dibolisporites, and in particular Dibolisporites echinaceus, Dictyotriletes canadensis, Emphanisporites annulatus, E. erraticus, and E. schultzii that indicate the Red Island Road Formation was deposited during the early and early late Emsian Emphanisporites annulatus – Camarozonotriletes sextantii Assemblage Zone. Biostratigraphy places age constraints on Acadian tectonism, local thrusting, and foreland basin development in this part of the Anticosti Basin. The suite of clasts indicates a radical shift in provenance as compared with siliciclastic units lower in the foreland basin sequence. Clearly, the source for these clasts is not local. Terranes farther afield, such as the La Poile Group in southwestern Newfoundland, should be examined as possibilities for the provenance of these rocks.

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