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.

Mesozoic compressional to extensional tectonics in the Central East Iranian Microcontinent: evidence from the Boneh Shurow Metamorphic Core Complex

2021 ◽  
pp. jgs2020-123
Author(s):  
Masoumeh Soleimani ◽  
Ali Faghih ◽  
Timothy Kusky
Keyword(s):  
Shear Zones ◽  
Metamorphic Core Complex ◽  
Crustal Thickening ◽  
Core Complex ◽  
Tectonic Events ◽  
Field Evidence ◽  
Ductile Shear Zones ◽  
Deformation Event ◽  
Tethys Ocean ◽  
Metamorphic Core

The Boneh Shurow metamorphic core complex (BSMCC) in the Central East Iranian Microcontinent (CEIM) provides a good example of the Mesozoic succession of nonsynchronous compressional and extensional deformation events attributed to the transitional Cimmerian events. The D1 compression developed subvertical dextral ductile shear zones and corresponds to continental accretion and crustal thickening producing kyanite- and sillimanite-grade rocks and migmatites in the Early Cimmerian orogeny in the CEIM. The D2 deformation event is marked by extension during the mid-Cimmerian orogeny. It is characterized by top-to-the-NE normal sense of shear along a low angle detachment surface. Field evidence for cross cutting relationships of D1- by D2-related structures reveal that the occurrence of Barrovian facies metamorphism and associated partial melting in the core of BSMCC formed during compressional tectonic events. These structures formed before the initiation of extension and the formation of the low-angle detachment shear zone. Finally, during the Late Cimmerian D3 event, the east and west Boneh Shurow reverse faults ruptured on both sides of the MCC. Recognition of the complicated origin and exhumation mechanisms of the BSMCC provide crucial constraints on the prolonged evolution of Paleo- and Neo-Tethys ocean basins and collisional and post-collisional events in this region.

scholarly journals A Review of Boron-Bearing Minerals (Excluding Tourmaline) in the Adirondack Region of New York State

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 644 ◽  
Author(s):  
David G. Bailey ◽  
Marian V. Lupulescu ◽  
Robert S. Darling ◽  
Jared W. Singer ◽  
Steven C. Chamberlain
Keyword(s):  
New York ◽  
New York State ◽  
Grenville Province ◽  
York State ◽  
Metasedimentary Rocks ◽  
Upstate New York ◽  
Geological Processes ◽  
Boron Minerals ◽  
Metamorphic Terranes ◽  
Raman Spectral Data

Boron is a biologically important element, but its distribution in the natural environment and its behavior during many geological processes is not fully understood. In most metamorphic and igneous environments, boron is incorporated into minerals of the tourmaline supergroup. In high-grade metamorphic terranes like that of the Adirondack region of northern New York State, uncommon rock compositions combined with unusual and variable geologic conditions resulted in the formation of many additional boron-bearing minerals. This paper reviews the occurrences and geological settings of twelve relatively uncommon boron-bearing minerals in the southern Grenville Province of upstate New York and provides new chemical and Raman spectral data for seven of these minerals. The boron minerals range from relatively simple metal borates (e.g., vonsenite), to chemically complex borosilicates (e.g., prismatine), to a relatively rare borosilicate-carbonate (e.g., harkerite). Some are of primary igneous origin, while others are formed by a variety of prograde and retrograde metamorphic processes or by metasomatic/hydrothermal processes. Most of the boron minerals are formed within, or adjacent to, metasedimentary lithologies that surround the anorthositic massifs of the central Adirondacks. The metasedimentary rocks are thought to be the source of most of the boron, although additional boron isotope studies are needed to confirm this and to constrain the mechanisms of the formation of these unusual minerals.

Sign in / Sign up

Export Citation Format

Share Document