Early Paleozoic development of the Maine-Quebec Boundary Mountains region

2006 ◽  
Vol 43 (3) ◽  
pp. 367-389 ◽  
Author(s):  
C C Gerbi ◽  
S E Johnson ◽  
J N Aleinikoff ◽  
J H Bédard ◽  
G R Dunning ◽  
...  
Keyword(s):  
New England ◽  
Passive Margin ◽  
Geochemical Data ◽  
Early Paleozoic ◽  
Mountain Building ◽  
Appalachian Mountain ◽  
Early Ordovician ◽  
History Of

Pre-Silurian bedrock units played key roles in the early Paleozoic history of the Maine–Quebec Appalachians. These units represent peri-Laurentian material whose collision with the craton deformed the Neoproteozoic passive margin and initiated the Appalachian mountain-building cycle. We present new field, petrological, geochronological, and geochemical data to support the following interpretations related to these units. (1) The Boil Mountain Complex and Jim Pond Formation do not represent part of a coherent ophiolite. (2) Gabbro and tonalite of the Boil Mountain Complex intruded the Chain Lakes massif at ca. 477 Ma. (3) The Skinner pluton, an arc-related granodiorite, intruded the Chain Lakes massif at ca. 472 Ma. (4) The Attean pluton, with a reconfirmed age of ca. 443 Ma, is unrelated to Early Ordovician orogenesis. (5) The most likely timing for the juxtaposition of the Jim Pond Formation and the Boil Mountain Complex was during regional Devonian deformation. These interpretations suggest that the Boundary Mountains were once part of a series of arcs extending at least from central New England through Newfoundland.

Zircon U–Pb ages and Lu–Hf isotopes of metagranitoids from the Subansiri region, Eastern Himalaya: implications for crustal evolution along the northern Indian passive margin in the early Paleozoic

2018 ◽  
Vol 481 (1) ◽  
pp. 299-318 ◽  
Author(s):  
R. K. Bikramaditya ◽  
A. Krishnakanta Singh ◽  
Sun-Lin Chung ◽  
Rajesh Sharma ◽  
Hao-Yang Lee
Keyword(s):  
Experimental Period ◽  
Mineral Chemistry ◽  
Hf Isotope ◽  
Passive Margin ◽  
Hf Isotopes ◽  
Eastern Himalaya ◽  
Geochemical Data ◽  
Early Paleozoic ◽  
Content Type ◽  
Supplementary Material

AbstractWe studied the zircon U–Pb ages, Hf isotopes, and whole-rock and mineral chemistry of metagranitoids from the Subansiri region of the Eastern Himalaya to constrain their emplacement age, origin and geodynamic evolution. The investigated metagranitoids have high SiO2, Na2O + K2O, Rb, Zr and low Fe2O3, Nb, Ga/Al ratios with fractionated rare earth element patterns [(Ce/Yb)N = 6.46–42.15] and strong negative Eu anomalies (Eu/Eu* = 0.16–0.44). They are peraluminous (molar A/CNK = 1.04–1.27) and calc-alkaline in nature, with normative corundum (1.04–3.61) and relatively high FeOt/MgO ratios in biotite (c. 3.38), indicating their affinity with S-type granites. The time of emplacement of the Subansiri metagranitoids is constrained by zircon U–Pb ages between 516 and 486 Ma. The zircon grains have negative εHf(t) values ranging from −1.4 to −12.7 and yield crustal Hf model ages from 1.5 to 2.2 Ga, suggesting the occurrence of a major crustal growth event in the Proterozoic and re-melting of the crust during the early Paleozoic. The geochemical data in conjunction with the U–Pb ages and Hf isotope data suggest that the Subansiri metagranitoids were produced by partial melting of older metasedimentary rocks in the Indian passive margin.Supplementary material: Hf isotope results for the Mud Tank zircon standard acquired during the experimental period are available at https://doi.org/10.6084/m9.figshare.c.4299830

Chilliwack composite terrane in northwest Washington: Neoproterozoic–Silurian passive margin basement, Ordovician–Silurian arc inception

2010 ◽  
Vol 47 (10) ◽  
pp. 1347-1366 ◽  
Author(s):  
E. H. Brown ◽  
G. E. Gehrels ◽  
V. A. Valencia
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Complex Problem ◽  
Late Ordovician ◽  
Detrital Zircons ◽  
Passive Margin ◽  
Early Paleozoic ◽  
Intrusive Rocks ◽  
History Of ◽  
Detrital Zircon Ages

The Chilliwack composite terrane in northwest Washington is part of an assemblage of mid-Paleozoic arc terranes extending from California to Alaska. Some terranes bear evidence of exotic origin, whereas others apparently formed proximal to western Laurentia, posing a complex problem in unraveling the Paleozoic accretionary history of the Cordillera. In our proposed broader definition, the Chilliwack composite terrane includes the volcanic and sedimentary East Sound and Chilliwack groups, and the plutonic and metamorphic Turtleback and Yellow Aster complexes. New zircon ages indicate that the plutonic and volcanic rocks are mutually related as parts of the same arc complex and that its inception was as old as Late Ordovician to Silurian, older than most other parts of the mid-Paleozoic terrane assemblage. Basement to the arc complex is a passive margin assemblage of metamorphosed quartzose sandstone and calc-silicate rock of the Yellow Aster Complex, bracketed in age by ca. 1000 Ma detrital zircons and 418 Ma intrusive rocks. This association of paragneiss basement and overlying and (or) intruding arc resembles that of older parts of the extensive Yukon–Tanana terrane in the northern Cordillera. Detrital zircon ages support a western Laurentian pericratonic origin for the paragneiss basement and the overlying arc. However, an early to mid-Paleozoic connection of this assemblage to the exotic outboard Alexander terrane is also indicated, based on (1) Mesoproterozoic and early Paleozoic detrital zircons in Devonian sedimentary rocks of the arc, and also in certain other pericratonic Devonian terranes and strata of the miogeocline; (2) Late Ordovician – Silurian igneous ages; and (3) an earliest Devonian or older metamorphic age of the basement paragneiss.

scholarly journals The City-State of Boston: The Rise and Fall of an Atlantic Power, 1630–1865

2020 ◽  
Vol 94 (3) ◽  
pp. 631-636
Author(s):  
Noam Maggor
Keyword(s):  
New England ◽  
British Empire ◽  
American Revolution ◽  
Regional Autonomy ◽  
Atlantic Trade ◽  
History Of ◽  
British Colonial ◽  
City State ◽  
The City ◽  
American Nation

Mark Peterson's The City-State of Boston is a formidable work of history—prodigiously researched, lucidly written, immense in scope, and yet scrupulously detailed. A meticulous history of New England over more than two centuries, the book argues that Boston and its hinterland emerged as a city-state, a “self-governing republic” that was committed first and foremost to its own regional autonomy (p. 6). Rather than as a British colonial outpost or the birthplace of the American Revolution—the site of a nationalist struggle for independence—the book recovers Boston's long-lost tradition as a “polity in its own right,” a fervently independent hub of Atlantic trade whose true identity placed it in tension with the overtures of both the British Empire and, later, the American nation-state (p. 631).

CLINICAL CONFERENCE

PEDIATRICS ◽  
1958 ◽  
Vol 22 (5) ◽  
pp. 1016-1022
Author(s):  
Saul Krugman ◽  
Robert Ward
Keyword(s):  
England Journal ◽  
New England ◽  
Gamma Globulin ◽  
Infectious Hepatitis ◽  
Progress Report ◽  
State School ◽  
Staten Island ◽  
Active Immunity ◽  
History Of ◽  
Time Of Admission

Dr. Krugman: Since 1953 approximately 400 cases of infectious hepatitis with jaundice have been observed at the Willowbrook State School on Staten Island. The studies to be described were carried out in collaboration with Dr. Robert Ward and Dr. Joan Giles of our staff, Dr. A. Milton Jacobs of Willowbrook State School and Dr. Oscar Bodansky of Sloan-Kettering Institute. I should like to present a progress report of our investigations which have been concerned with the prevention and natural history of infectious hepatitis at Willowbrook. (A report of these studies has recently appeared in the New England Journal of Medicine (248:407, 1958) to which the reader may refer for further details.) It had been previously reported by Stokes and associates that the administration of gamma-globulin was followed by not only a lower incidence of hepatitis but also a prolongation of the protective effect. Stokes postulated that "passive-active" immunity was responsible for this phenomenon. The epidemic of hepatitis at Willowbrook provided us with an opportunity to test this hypothesis. Effect of Gamma-globulin on the Frequency of Infectious Hepatitis. Figure 1 illustrates the course of the outbreak at Willowbrook beginning in January, 1955. As can be seen, hepatitis continued to occur at a rate of about two to three cases per week. The cases, predominantly in children, occurred in 18 buildings in the institution. In June of 1956 gamma-globulin, 0.01 ml/lb, was administered to approximately a third of the inmates of each building. The control and inoculated groups were comparable as to age and time of admission to Willowbrook.

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