scholarly journals Syn-collisional exhumation of hot middle crust in the Adirondack Mountains (New York, USA): Implications for extensional orogenesis in the southern Grenville province

Geosphere ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1240-1261 ◽  
Author(s):  
S.P. Regan ◽  
G.J. Walsh ◽  
M.L. Williams ◽  
J.R. Chiarenzelli ◽  
M. Toft ◽  
...  
Keyword(s):  
New York ◽  
Fluid Flow ◽  
Structural Evolution ◽  
Granite Gneiss ◽  
Shear Zones ◽  
Ore Deposits ◽  
Adirondack Mountains ◽  
Grenville Province ◽  
Granulite Facies Metamorphism ◽  
Detachment Zone

Abstract Extensional deformation in the lower to middle continental crust is increasingly recognized and shown to have significant impact on crustal architecture, magma emplacement, fluid flow, and ore deposits. Application of the concept of extensional strain to ancient orogenic systems, like the Grenville province of eastern North America, has helped decipher the structural evolution of these regions. The Marcy massif is a ∼3000 km2 Mesoproterozoic anorthosite batholith in the Adirondack Mountains (New York, USA) of the southern Grenville province. Bedrock geology mapping at 1:24,000 scale paired with characterization of bedrock exposed by recent landslides provides a glimpse into the structural architecture of the massif and its margin. New data demonstrate granulite- to amphibolite-facies deformational fabrics parallel the margin of the batholith, and that the Marcy massif is draped by a southeast-directed detachment zone. Within the massif, strain is localized into mutually offsetting conjugate shear zones with antithetic kinematic indicators. These relationships indicate that strain was coaxial within the Marcy massif, and that subsimple shear components of strain were partitioned along its margin. In situ U–Th–total Pb monazite analysis shows that deformation around and over the Marcy massif occurred from 1070 to 1060 Ma during granulite-facies metamorphism, and monazite from all samples record evidence for fluid-mediated dissolution reprecipitation from 1050 to 980 Ma. We interpret that rocks cooled isobarically after accretionary orogenesis and emplacement of the anorthosite-mangerite-charnockite-granite plutonic suite at ca. 1160–1140 Ma. Gravitational collapse during the Ottawan phase of the Grenville orogeny initiated along a southeast-directed detachment zone (Marcy massif detachment zone), which accommodated intrusion of the Lyon Mountain Granite Gneiss, and facilitated substantial fluid flow that catalyzed the formation of major ore deposits in the Adirondack Highlands.

scholarly journals Late Ottawan orogenic collapse of the Adirondacks in the Grenville province of New York State (USA): Integrated petrologic, geochronologic, and structural analysis of the Diana Complex in the southern Carthage-Colton mylonite zone

Geosphere ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 844-874
Author(s):  
Graham B. Baird
Keyword(s):  
New York ◽  
Pure Shear ◽  
New York State ◽  
Shear Zones ◽  
Core Complex ◽  
Grenville Province ◽  
York State ◽  
Mylonite Zone ◽  
Ductile Shear Zones ◽  
Metamorphic Core

Abstract Crustal-scale shear zones can be highly important but complicated orogenic structures, therefore they must be studied in detail along their entire length. The Carthage-Colton mylonite zone (CCMZ) is one such shear zone in the northwestern Adirondacks of northern New York State (USA), part of the Mesoproterozoic Grenville province. The southern CCMZ is contained within the Diana Complex, and geochemistry and U-Pb zircon geochronology demonstrate that the Diana Complex is expansive and collectively crystallized at 1164.3 ± 6.2 Ma. Major ductile structures within the CCMZ and Diana Complex include a northwest-dipping penetrative regional mylonitic foliation with north-trending lineation that bisects a conjugate set of mesoscale ductile shear zones. These ductile structures formed from the same 1060–1050 Ma pure shear transitioning to a top-to-the-SSE shearing event at ∼700 °C. Other important structures include a ductile fault and breccia zones. The ductile fault formed immediately following the major ductile structures, while the breccia zones may have formed at ca. 945 Ma in greenschist facies conditions. Two models can explain the studied structures and other regional observations. Model 1 postulates that the CCMZ is an Ottawan orogeny (1090–1035 Ma) thrust, which was later reactivated locally as a tectonic collapse structure. Model 2, the preferred model, postulates that the CCMZ initially formed as a subhorizontal mid-crustal mylonite zone during collapse of the Ottawan orogen. With continued collapse, a metamorphic core complex formed and the CCMZ was rotated into is current orientation and overprinted with other structures.

Precise zircon geochronology in the Adirondack Lowlands and implications for revising plate-tectonic models of the Central Metasedimentary Belt and Adirondack Mountains, Grenville Province, Ontario and New York

1999 ◽  
Vol 36 (6) ◽  
pp. 967-984 ◽  
Author(s):  
Hardolph Wasteneys ◽  
James McLelland ◽  
Sydney Lumbers
Keyword(s):  
New York ◽  
Plate Tectonic ◽  
Adirondack Mountains ◽  
Grenville Province ◽  
Metasedimentary Rocks ◽  
Minimum Age ◽  
Single Grain ◽  
Shrimp Zircon ◽  
Shrimp Zircon Dating ◽  
St Lawrence River

New high-precision, single-grain dating of leucogranites from the Adirondack Lowlands, dated previously by multigrain zircon methods at ca. 1416 Ma (Wellesley Island) and ca. 1285-1230 Ma (Hyde School Gneiss), has yielded U-Pb zircon ages of ca. 1172 Ma, identical to that of Rockport granite of the Frontenac terrane. In addition, sensitive high resolution ion microprobe (SHRIMP) zircon dating of the intrusive Antwerp-Rossie suite in the Adirondack Lowlands indicates a maximum emplacement age of ca. 1207+26-11 Ma which fixes a minimum age for deposition of regional metasedimentary rocks that it crosscuts. These results remove apparent chronological discrepancies across the St. Lawrence River, thus expanding the significance of the Rockport granite and Hyde School Gneiss and requiring modification of plate-tectonic models for the Central Metasedimentary Belt and Adirondack Mountains in the interval ca. 1350-1125 Ma.

scholarly journals Geologic transect across the Grenville orogen of Ontario and New York

2000 ◽  
Vol 37 (2-3) ◽  
pp. 193-216 ◽  
Author(s):  
S D Carr ◽  
R M Easton ◽  
R A Jamieson ◽  
N G Culshaw
Keyword(s):  
New York ◽  
Cross Sections ◽  
Shear Zones ◽  
Normal Faults ◽  
Grenville Province ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Seismic Reflectivity ◽  
Granitoid Rocks ◽  
Laurentian Margin

Revised cross sections of the western Grenville Province incorporate new geologic results and reprocessed seismic reflection data. The geology is presented in terms of three tectonic elements: (1) "pre-Grenvillian Laurentia and its margin" with ca. 1740 and 1450 Ma continental arc plutons and associated supracrustal rocks; (2) "Composite Arc Belt" of allochthonous ~1300-1250 Ma volcanic arcs and sedimentary rocks; and (3) "Frontenac-Adirondack Belt" characterized by supracrustal and granitoid rocks, and anorthosites, of uncertain affinity, that may represent a distinctive part of the Composite Arc Belt or an offshore (micro)continent. Rocks of the Composite Arc and Frontenac-Adirondack belts were amalgamated with each other by ca. 1160 Ma, were then thrust over Laurentia during ca. 1080-1035 Ma and ca. 1010-980 Ma phases of convergence, and were dissected and exhumed by <1040 Ma normal faults. Penetrative deformation was restricted to that part of the pre-Grenvillian Laurentian margin that lies to the southeast of the Grenville front and parts of the accreted Composite Arc and Frontenac-Adirondack belts. The Laurentian rocks in the Grenville Province are bounded to the northwest and southeast by southeast-dipping ductile thrust and (or) normal shear zones. The Composite Arc and Frontenac-Adirondack belts to the southeast are bounded by ductile and brittle-ductile thrust and (or) normal faults that separate domains with contrasting cooling histories. Despite a long pre-Grenvillian tectonic and plutonic history, the present crustal architecture and much of the seismic reflectivity were acquired during 1080-980 Ma phases of compression and extension.

scholarly journals The Kilmar Magnesite Deposits: Evaporitic Metasediments in the Grenville Supergroup, Morin Terrane, Quebec

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 554 ◽  
Author(s):  
Peck ◽  
Eppich
Keyword(s):  
New York ◽  
Stable Isotope ◽  
Isotope Ratios ◽  
Granulite Facies ◽  
Ore Deposits ◽  
Depositional Environments ◽  
Dolomitic Marble ◽  
Grenville Province ◽  
Metasedimentary Rocks ◽  
Δ18o And Δ13c

Mesoproterozoic magnesite deposits are found associated with dolomitic marble and intercalated with metasedimentary rocks of the Grenville Supergroup in the granulite facies Morin terrane (Grenville Province, Quebec). This study examines one of the remaining ore deposits exposed on the surface (at the Dobbie mine), and presents stable isotope and mineralogical data for a marine evaporitic origin. The magnesite ore zone has δ18O(Mag) = 25.5 ± 0.4‰ (VSMOW) and δ13C(Mag) = 1.7 ± 0.2‰ (VPDB; n = 7), while surrounding dolomitic marble has δ18O(Dol) = 24.2 ± 0.6‰ and δ13C(Dol) = −0.2 ± 0.7‰ (n = 11). These values are at the high end of the range for other Morin terrane marbles, and this and sharp transitions in stable isotope ratios between lithologies argue for preservation of evaporitic enrichment in δ18O and δ13C. Boron isotope ratios (δ11B = 15.5‰ to 22.7‰) are also consistent with a marine evaporite origin. Identifying evaporitic protoliths in metasedimentary rocks is important for determining pre-metamorphic depositional environments, and in this case links the sedimentary setting of the Morin terrane to the Adirondack Lowlands (New York, NY, USA). The identification of the Kilmar magnesite deposits as evaporitic also has implications for the formation of sedimentary exhalative base metal deposits in the Grenville Supergroup.

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