The geochronology of some stratified metamorphic rocks in northeastern Massachusetts

1980 ◽  
Vol 17 (10) ◽  
pp. 1407-1416 ◽  
Author(s):  
William J. Olszewski Jr.
Keyword(s):  
New England ◽  
Source Area ◽  
Detrital Zircons ◽  
Metamorphic Rocks ◽  
Thermal Event ◽  
Northwest Africa ◽  
Major Period

Analyses of U and Pb in zircons and Rb and Sr in whole rocks have been made on stratified metamorphic rocks in northeastern Massachusetts. The Rb–Sr results show an age of about 450 Ma, which is interpreted as a resetting age. This would indicate the major period of metamorphism in the area. Zircons from the Fishbrook Gneiss give an upper intercept age of 730 ± 26 Ma, which is interpreted as the age of volcanism that produced the Fishbrook Gneiss sequence. The upper intercept of the Westboro Formation detrital zircons is 1511 ± 22 Ma and is interpreted as the age of the source for the Westboro sediments. The lower intercepts of the Fishbrook (289 Ma) and the Westboro (278 Ma) zircons suggest an episodic Pb loss correlated with the thermal event in southeastern New England recognized by other methods. The intercept ages of the Shawsheen Gneiss (2042 and 517 Ma) are more difficult to interpret, but also suggest an old source area. This source area is tentatively suggested to be northwest Africa.

scholarly journals Provenance of sediments from Barra del Tordo and Tesoro beaches, Tamaulipas State, northwestern Gulf of Mexico

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Mayla A. Ramos-Vázquez ◽  
John S. Armstrong-Altrin
Keyword(s):  
Gulf Of Mexico ◽  
Age Groups ◽  
Source Area ◽  
Detrital Zircons ◽  
Sediment Provenance ◽  
Geochemical Composition ◽  
Chemical Index ◽  
Beach Sediments ◽  
Chemical Index Of Alteration ◽  
Ree Patterns

AbstractThe mineralogy, bulk sediment geochemical composition, and U–Pb ages of detrital zircons retrieved from the Barra del Tordo (Tordo) and Tesoro beach sediments in the northwestern Gulf of Mexico were analyzed to determine their provenance. The beach sediments are mainly composed of quartz, ilmenite, magnetite, titanite, zircon, and anorthite. The weathering proxies such as the Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA), reveal a moderate-to-high intensity of weathering in the source area. The chondrite-normalized rare earth element (REE) patterns are similar to felsic igneous rocks, with large negative europium anomaly (Eu/Eu* = ~ 0.47–0.80 and ~ 0.57–0.67 in the Tordo and Tesoro beach sediments, respectively).Three major zircon U–Pb age groups are identified in the Tordo and Tesoro beach sediments, i.e., Proterozoic (~ 2039–595 Ma), Mesozoic (~ 244–70.3 Ma), and Cenozoic (~ 65.9–1.2 Ma). The differences of the zircon age spectrum between the Tordo and Tesoro beach sediments are not significant. The comparison of zircon U–Pb ages in this study with ages of potential source terranes suggests that the Mesozoic and Cenozoic zircons of the studied Tordo and Tesoro beach sediments were derived from the Eastern Alkaline Province (EAP) and Mesa Central Province (MCP). Similarly, the likely sources for the Proterozoic zircons were the Sierra Madre Oriental (SMOr) and Oaxaquia in the northwestern Gulf of Mexico. The results of this study further indicate that the sediments delivered to the beaches by rivers and redistributed by longshore currents were crucial in determining the sediment provenance.

Resistance of zircons to U–Pb resetting in a prograde metamorphic sequence of Caledonian age in East Greenland

1985 ◽  
Vol 22 (3) ◽  
pp. 330-338 ◽  
Author(s):  
J. J. Peucat ◽  
D. Tisserant ◽  
R. Caby ◽  
N. Clauer
Keyword(s):  
Source Area ◽  
Detrital Zircons ◽  
Metamorphic Event ◽  
Great Resistance ◽  
East Greenland ◽  
Geological Interpretation ◽  
Source Areas ◽  
Metasedimentary Rocks ◽  
Sedimentary Source

In the Alpefjord area, Caledonian metamorphism from the chlorite zone to the sillimanite zone is seen to cut across the sedimentary pile of the lower Eleonore Bay Group. Zircons have been collected from quartzite layers enriched in heavy minerals.U–Pb zircon dating in the chlorite and the sillimanite zones does not reveal the Caledonian event but, instead, previous episodes at 1100 and 2500 Ma ago. The Caledonian event can be recognized in anatectic gneisses where detrital zircons are surrounded by overgrowths, K–Ar and Rb–Sr methods yield 1030–410 Ma ages on micas, with a positive correlation between the degree of apparent reselling of mica ages and the grade of the Caledonian metamorphism.The following geological interpretation of the age data is proposed. (1) A major metamorphic event occurred around 1100 Ma ago in the source area for the lower Eleonore Bay Group sediments. During this Grenvillian event, Archaean detrital zircons were affected by an episodic lead loss and a muscovite phase recorded the cooling and uplift of a basement source area. (2) Erosion of this source area occurred after 1100 Ma, followed by sedimentation of the lower Eleonore Bay Group [Formula: see text]. The 2500–1100 Ma U–Pb system remained nearly a closed system during Caledonian metamorphism up to and including sillimanite-zone conditions.This example shows the great resistance or inherited zircons to an important secondary Pb loss during Caledonian metamorphism and consequently shows that the lower-intercept ages of zircons from metasedimentary rocks do not always record the last metamorphic event observed in situ, but retain memories of previous geological events in the sedimentary source areas. By contrast, zircons separated from quartzitic xenoliths in migmatitic gneisses have recorded a disturbance in their U–Pb systems that corresponds to Caledonian partial melting.

Jurassic-Cretaceous paleogeography of Central-West Parnaiba Basin, NE Brazil - stratigraphy and sedimentary provenance of detrital zircons

2020 ◽  
Author(s):  
André Pereira de Assis ◽  
Kelly Aparecida Caldas da Cruz ◽  
Renata da Silvia Schmitt ◽  
Silvia Regina de Medeiros
Keyword(s):  
Detrital Zircon ◽  
Source Area ◽  
Depositional Environments ◽  
Detrital Zircons ◽  
Hypersaline Lake ◽  
Red Sandstone ◽  
Source Areas ◽  
Aeolian Dunes ◽  
Marine Ingression ◽  
And Shifts

<p><span>The Phanerozoic Parnaíba Basin occupies 600.000km² in northeast Brazil, covering cratons and Neoproterozoic belts. Its Central-West region is mostly represented by the Jurassic-Cretaceous Sequence (Mosquito, Corda Grajaú, Codó and Itapecuru formations) recording magmatic events from the Central Atlantic Magmatic Province, with depocenters migrations and shifts on depositional environments related to Pangea breakup.<span>  </span>This work discusses the Jurassic-Cretaceous siliciclastic units testing possible sedimentary source areas with U-Pb and combined Lu-Hf data on detrital zircons, using LA-ICP-MS. The basalts from Mosquito Formation are dated at +/- 198Ma and the Codó Formation present accurate Aptian fossil data. This formation records a hypersaline lake system, succeeded by a transgression that represents pioneer marine ingression within an intracontinental rift. The other units (Corda, Grajaú and Itapecuru) are constituted by siliciclastic sediments involved in intracontinental sub-environments. The Corda Formation consists of aeolian system, sand sheets and <em>wadis</em> deposited in a desertic setting. The contact between the subsequent Grajaú Formation is abrupt, represented, at the base, by thick coarse braided river facies grading laterally and upwards to ephemeral channels in association with low amplitude Aeolian dunes, evidencing still arid conditions. Interlayered beds of fluvial and aeolian sandstones within lacustrine deposits, indicates that Codó and Grajaú formations consists the same seasonal fluvial-lacustrine system. The last Itapecuru Formation, is represented by a thick red sandstone succession deposited in a deltaic system. Paleocurrents measurements below Codó Formation (i.e. Corda and lower Grajaú) points a W-NW sense of direction, whereas paleocurrents above Codó Formation (i.e. upper Grajaú and Itapecuru) presents a regional sense to E-NE. Detrital zircons geochronology analysis helped to identify the source area of sediments through the comparison of the main ages of possible uplifted tectonic terranes. The preliminary results revealed that sandstones below Codó Formation shows a major Neoproterozoic population (56, 41% to 40%) with age peaks at 583 and 628 Ma; and also Paleoproterozoic (43, 48% to 35,05%); Archean (4,35%) and Paleozoic (2,61%) populations. Sandstones above Codó Formation, also show a Neoproterozoic major detrital zircon population (40% to 37,12%) with 625, 665 and 783 Ma age peaks. Two other populations are present: Paleoproterozoic (22.68% to 20%) with peaks at 1749 and 1881 Ma, and Archean (24,45% to 15,47%). This last source has a greater contribution than in the formations below the Codó maker. We envisaged that the shift from W-NW to E-NE sandstones paleocurrent is coherent with the rise on Archean contribution, possibly related to the Amazon Craton to the West. In addition, the youngest Phanerozoic detrital zircons obtained in all samples are minor (6,66% to 6,18%). The integration of field stratigraphic analysis, paleocurrents and detrital zircon provenance studies corroborate to the hypothesis that Codó Formation must represent a Cretaceous stratigraphic datum for the transition of a rift and post-rift phase, thus the change of source areas is consistent. </span></p><p><span>The authors acknowledge support from Shell Brasil Petroleo Ltda. and ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation (Technichal Cooperation #20.219-2).</span></p>

A model for the origin of the Lac St. Jean anorthosite massif

1976 ◽  
Vol 13 (2) ◽  
pp. 389-399 ◽  
Author(s):  
R. A. Frith ◽  
K. L. Currie
Keyword(s):  
Experimental Data ◽  
Partial Melting ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Calc Alkaline ◽  
Grenville Province ◽  
Thermal Event ◽  
Anorthosite Massif ◽  
Mineral Assemblages ◽  
Potassic Rocks

An ancient tonalitic complex becomes migmatitic around the Lac St. Jean massif, ultimately losing its identity in the high grade metamorphic rocks surrounding the anorthosite. Field relations suggest extreme metamorphism and anatexis of tonalitic rocks. Experimental data show that extensive partial melting of the tonalite leaves an anorthositic residue. The same process operating on more potassic rocks would leave monzonitic or quartz syenitic residues. Synthesis of experimental data suggests that the process could operate at pressures of 5–8 kbar and temperatures of 800–1000 °C, which are compatible with mineral assemblages around the anorthosite massif. Slightly higher temperatures at the end of the process could generate magmatic anorthosite.Application of the model to the Grenville province as a whole predicts generation of anorthosite during a long-lived thermal event of unusual intensity. Residual anorthosite would occur as a substratum in the crust, overlain by high-grade metamorphic rocks intruded by anorthosite and syenitic rocks, while higher levels in the crust would display abundant calc-alkaline plutons and extrusives.

scholarly journals SHRIMP U-Pb dating of detrital zircons in metamorphic rocks from northern Kyushu, western Japan

2003 ◽  
Vol 98 (5) ◽  
pp. 181-193 ◽  
Author(s):  
Yukiyasu TSUTSUMI ◽  
Kazumi YOKOYAMA ◽  
Kentaro TERADA ◽  
Yuji SANO
Keyword(s):  
Detrital Zircons ◽  
Metamorphic Rocks ◽  
Western Japan

scholarly journals Heavy Minerals as Indicators of the Source and Stratigraphic Position of the Loess-Like Deposits in the Orava Basin (Polish Western Carpathians)

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 445
Author(s):  
Dorota Chmielowska ◽  
Dorota Salata
Keyword(s):  
Source Area ◽  
Heavy Mineral ◽  
Source Rocks ◽  
Heavy Minerals ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Tatra Mountains ◽  
Stratigraphic Position ◽  
Glacial Periods ◽  
The Tatra Mountains

This study is focused on the loess-like deposits accumulated on glaciofluvial fans of the Czarny Dunajec River in the Orava Basin (Southern Poland). The deposition of these sediments took place during three cold intervals of the Pleistocene: Würm, Riss, and Günz/Mindel. So far, the provenance and age of the deposits has not been precisely defined, even though the development of each fan is believed to be related to the successive glacial periods in the Tatra Mountains. Heavy minerals were studied to determine the source of the deposits. Heavy mineral analyses revealed that zircon, tourmaline, rutile, garnet, amphibole, epidote, and apatite are the typical constituents of the heavy mineral fraction. Abundances of heavy minerals differ in each of the Pleistocene fans of the Czarny Dunajec River, especially the amphibole content. However, the chemical composition of garnet, amphibole, and tourmaline is rather uniform. This research showed that mainly medium-grade metamorphic rocks with a subordinate share of high-grade metamorphics, and granitic rocks are the dominant source rocks of the deposits studied. Such rocks are exposed in the Western Tatra Mountains, which most probably supplied the Orava Basin with clastic material. Change in abundances of heavy minerals in the succession may reflect the progressive erosion of the source area. Grain-size distribution and textural features of the sampled sediments suggest fluvial and aeolian modes of transportation. Additionally, this study indicated that heavy minerals may be used to correlate the loess covers in the Orava Basin.

Tracking Recent DDT Contamination in a Northern New England Watershed

2021 ◽  
Author(s):  
Amanda May ◽  
Lisa Doner ◽  
Jeremiah Duncan ◽  
Stephen Hill
Keyword(s):  
New England ◽  
New Hampshire ◽  
Sediment Quality ◽  
Source Area ◽  
Daughter Product ◽  
Multiple Sources ◽  
Aquatic Life ◽  
Quality Guidelines ◽  
Northern New England ◽  
Lake Deposits

Abstract Ecological research since 2005 into potential causes of declines in loon population at Squam Lake, New Hampshire, U.S.A., revealed multiple potential causes, but no particular source of contaminants. In 2017, tributary sediment analyses revealed specific sub-watersheds transporting contaminants to the lake (Vogel, 2019). For this study, from 2018 to 2020, we used an approach to this problem that allowed for rapid source area determination of DDT using soil and sediment analyses. We find modern presence of p,p’ isomers of DDT and DDE within the Bennett Brook sub-watershed, arising from 60-year-old orchard applications and a former barn. Highest concentrations, 723 μg/kg p,p’ DDT and 721 μg/kg p,p’ DDE, occur near the barn’s foundation rubble. DDT exceeds that of the daughter product, DDE, in some of the sub-watershed’s soils, including but not limited to the barn site. In the soils where DDT>DDE, we infer delayed breakdown of DDT. DDT<DDE occurs in the streambed and lake deposits, as well as some soils. A Pb-210 dated sediment core, collected near the outlet of Bennet Brook, shows continuous accumulation of the daughter products, DDE and DDD, from 1951 to the present. Residuals are derived from multiple sources within the sub-watershed, including orchard soils, the barn site, and sediment accumulations in the stream. These DDT residues fall below mandatory soil remediation levels for the State of New Hampshire, but exceed some sediment quality guidelines for protection of aquatic life. Bioaccumulation of p,p’ DDE is evident in crayfish that reside in Bennett Brook.

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