scholarly journals ERRATUM: Suprasubduction zone ophiolite fragments in the central Appalachian orogen: Evidence for mantle and Moho in the Baltimore Mafic Complex (Maryland, USA)

Geosphere ◽  
2021 ◽  
Author(s):  
George L. Guice ◽  
Michael R. Ackerson ◽  
Robert M. Holder ◽  
Freya R. George ◽  
Joseph F. Browning-Hanson ◽  
...  
Keyword(s):  
Suprasubduction Zone ◽  
Mafic Complex ◽  
Appalachian Orogen

In the Table 3 note and captions of Figures 8 and 9, the equation Fe2+# = molar Fe2+/[Mg+Fe2++Fe3+] is incorrect. It should instead be Fe2+# = molar Fe2+/[Mg+Fe2+].

scholarly journals Suprasubduction zone ophiolite fragments in the central Appalachian orogen: Evidence for mantle and Moho in the Baltimore Mafic Complex (Maryland, USA)

Geosphere ◽  
2021 ◽  
Author(s):  
George L. Guice ◽  
Michael R. Ackerson ◽  
Robert M. Holder ◽  
Freya R. George ◽  
Joseph F. Browning-Hanson ◽  
...  
Keyword(s):  
New York ◽  
Tectonic Evolution ◽  
Mineral Chemistry ◽  
Bulk Rock ◽  
Suprasubduction Zone ◽  
Tectonic Processes ◽  
Iapetus Ocean ◽  
Mantle Peridotites ◽  
Mafic Complex ◽  
Appalachian Orogen

Suprasubduction zone (SSZ) ophiolites of the northern Appalachians (eastern North America) have provided key constraints on the fundamental tectonic processes responsible for the evolution of the Appalachian orogen. The central and southern Appalachians, which extend from southern New York to Alabama (USA), also contain numerous ultra- mafic-mafic bodies that have been interpreted as ophiolite fragments; however, this interpretation is a matter of debate, with the origin(s) of such occurrences also attributed to layered intrusions. These disparate proposed origins, alongside the range of possible magmatic affinities, have varied potential implications for the magmatic and tectonic evolution of the central and southern Appalachian orogen and its relationship with the northern Appalachian orogen. We present the results of field observations, petrography, bulk-rock geochemistry, and spinel mineral chemistry for ultramafic portions of the Baltimore Mafic Complex, which refers to a series of ultramafic-mafic bodies that are discontinuously exposed in Maryland and southern Pennsylvania (USA). Our data indicate that the Baltimore Mafic Complex comprises SSZ ophiolite fragments. The Soldiers Delight Ultramafite displays geochemical characteristics—including highly depleted bulk-rock trace element patterns and high Cr# of spinel—characteristic of subduction-related mantle peridotites and serpentinites. The Hollofield Ultramafite likely represents the “layered ultramafics” that form the Moho. Interpretation of the Baltimore Mafic Complex as an Iapetus Ocean–derived SSZ ophiolite in the central Appalachian orogen raises the possibility that a broadly coeval suite of ophiolites is preserved along thousands of kilometers of orogenic strike.

scholarly journals Supplemental Material: Suprasubduction zone ophiolite fragments in the central Appalachian orogen: Evidence for mantle and Moho in the Baltimore Mafic Complex (Maryland, USA)

2020 ◽  
Author(s):  
G.L. Guice ◽  
et al.
Keyword(s):  
Chemical Data ◽  
Bulk Rock ◽  
Standard Data ◽  
Suprasubduction Zone ◽  
Mafic Complex ◽  
Appalachian Orogen ◽  
Excel File

<div>Excel file containing bulk-rock and mineral chemical data, including standard data and precision calculations.<br></div>

scholarly journals Supplemental Material: Suprasubduction zone ophiolite fragments in the central Appalachian orogen: Evidence for mantle and Moho in the Baltimore Mafic Complex (Maryland, USA)

2020 ◽  
Author(s):  
G.L. Guice ◽  
et al.
Keyword(s):  
Chemical Data ◽  
Bulk Rock ◽  
Standard Data ◽  
Suprasubduction Zone ◽  
Mafic Complex ◽  
Appalachian Orogen ◽  
Excel File

<div>Excel file containing bulk-rock and mineral chemical data, including standard data and precision calculations.<br></div>

Bay of Islands and Little Port complexes, revisited: age, geochemical and isotopic evidence confirm suprasubduction-zone origin

1991 ◽  
Vol 28 (10) ◽  
pp. 1635-1652 ◽  
Author(s):  
G. A. Jenner ◽  
G. R. Dunning ◽  
J. Malpas ◽  
M. Brown ◽  
T. Brace
Keyword(s):  
Transform Fault ◽  
Isotopic Data ◽  
Isotopic Study ◽  
Zircon Age ◽  
Suprasubduction Zone ◽  
Mid Ocean Ridge ◽  
Appalachian Orogen ◽  
Ocean Ridge ◽  
Source Materials ◽  
Oceanic Domain

The Bay of Islands Complex of the Humber Arm allochthon, west Newfoundland, contains the best-exposed ophiolite in the Appalachian Orogen. Associated structural slices, the Little Port and Skinner Cove complexes, also contain rocks formed in an oceanic domain, although their relationship to the Bay of Islands Complex remains controversial.To constrain the origin of the complexes and obtain a better understanding of the geology of the Humber Arm allochthon, we have undertaken an integrated geochronological, geochemical, and isotopic study. A U/Pb zircon age of [Formula: see text] Ma for the Little Port Complex and a zircon and baddeleyite age of 484 ± 5 Ma for the Bay of Islands Complex have been obtained. Geochemical and isotopic data on trondhjemitic rocks from the two complexes indicate that petrogenetic models for these rocks must account for fundamental differences in source materials and mineralogy during differentiation. The Little Port Complex trondhjemites are characterized by initial εNd of −1 to +1, whereas those in the Bay of Islands have εNd of +6.5. Geochemical signatures in mafic and felsic volcanics of the complexes are diverse, and show a complete gradation between arc and non-arc.The Bay of Islands and Little Port complexes are not related by any form of a major mid-ocean-ridge – transform-fault model. An alternative model to explain the relationships between the two complexes interprets the Little Port as arc-related and the Bay of Islands as a suprasubduction-zone ophiolite.

THE BALTIMORE MAFIC COMPLEX, MARYLAND: OPHIOLITE FRAGMENTS IN THE SOUTHERN APPALACHIAN OROGEN?

2020 ◽  
Author(s):  
George Guice ◽  
◽  
Michael R. Ackerson ◽  
Robert Holder ◽  
Freya George ◽  
...  
Keyword(s):  
Southern Appalachian ◽  
Mafic Complex ◽  
Appalachian Orogen

Zircon geochronology and paleomagnetism of an Archean harzburgite intrusion, eastern Bighorn Mountains, Wyoming

2020 ◽  
Vol 57 (1) ◽  
pp. 21-40
Author(s):  
Alexandra Wallenberg ◽  
Michelle Dafov ◽  
David Malone ◽  
John Craddock
Keyword(s):  
Hanging Wall ◽  
Vertical Axis ◽  
Shear Zones ◽  
Strike Slip ◽  
Zircon Geochronology ◽  
Weighted Mean ◽  
Mafic Complex ◽  
Laramide Orogeny ◽  
Axis Rotation ◽  
Bighorn Mountains

A harzburgite intrusion, which is part of the trailside mafic complex) intrudes ~2900-2950 Ma gneisses in the hanging wall of the Laramide Bighorn uplift west of Buffalo, Wyoming. The harzburgite is composed of pristine orthopyroxene (bronzite), clinopyroxene, serpentine after olivine and accessory magnetite-serpentinite seams, and strike-slip striated shear zones. The harzburgite is crosscut by a hydrothermally altered wehrlite dike (N20°E, 90°, 1 meter wide) with no zircons recovered. Zircons from the harzburgite reveal two ages: 1) a younger set that has a concordia upper intercept age of 2908±6 Ma and a weighted mean age of 2909.5±6.1 Ma; and 2) an older set that has a concordia upper intercept age of 2934.1±8.9 Ma and a weighted mean age 2940.5±5.8 Ma. Anisotropy of magnetic susceptibility (AMS) was used as a proxy for magmatic intrusion and the harzburgite preserves a sub-horizontal Kmax fabric (n=18) suggesting lateral intrusion. Alternating Field (AF) demagnetization for the harzburgite yielded a paleopole of 177.7 longitude, -14.4 latitude. The AF paleopole for the wehrlite dike has a vertical (90°) inclination suggesting intrusion at high latitude. The wehrlite dike preserves a Kmax fabric (n=19) that plots along the great circle of the dike and is difficult to interpret. The harzburgite has a two-component magnetization preserved that indicates a younger Cretaceous chemical overprint that may indicate a 90° clockwise vertical axis rotation of the Clear Creek thrust hanging wall, a range-bounding east-directed thrust fault that accommodated uplift of Bighorn Mountains during the Eocene Laramide Orogeny.

Sign in / Sign up

Export Citation Format

Share Document