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>

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+].

Petrological studies of neoproterozoic serpentinized ultramafics of the nubian shield: spinel compositions as evidence of the tectonic evolution of egyptian ophiolites

2014 ◽  
Vol 64 (1) ◽  
pp. 123-137 ◽  
Author(s):  
Mokhles K. Azer
Keyword(s):  
Tectonic Evolution ◽  
Mantle Peridotite ◽  
Eastern Desert ◽  
Ultramafic Rocks ◽  
Chromian Spinel ◽  
Central Eastern Desert ◽  
Suprasubduction Zone ◽  
Mantle Peridotites ◽  
Nubian Shield ◽  
Ophiolitic Rocks

Abstract The mafic-ultramafic rocks of the Gabal El-Degheimi area, Central Eastern Desert of Egypt, are parts of an ophiolitic section. The ophiolitic rocks are dismembered and tectonically enclosed within, or thrust over, island arc assemblages. Serpentinites, altered slices of the upper mantle, represent a distinctive lithology of the dismembered ophiolites. Some portions of the serpentinized rocks contain fresh relicts of primary minerals such as chromian spinel and olivine. The abundance of bastite and mesh textures suggests harzburgite and dunite protoliths, respectively, for these serpentinites. Some fresh cores of chromian spinel are rimmed by ferritchromite and Cr-magnetite. The development of alteration rims around chromian spinel cores indicates their formation during prograde alteration and under oxidizing conditions during lower amphibolite facies metamorphism. Fresh chromian spinels are characterized by high contents of Cr2O3 (48.92-56.74 wt. %), Al2O3 (10.29-20.08wt. %), FeO (16.24-28.46 wt. %) and MgO (4.89-14.02 wt. %), and very low TiO2 contents (<0.16 wt. %). The analyzed fresh chromian spinels have high Cr# (0.62-0.79) characteristic of spinels in mantle peridotite that has undergone some degree of partial melting. The data presented here suggest that the mantle peridotites of the Gabal El-Degheimi area are similar to forearc peridotites of suprasubduction zone environments.

scholarly journals Tectonic Evolution of the SE West Siberian Basin (Russia): Evidence from Apatite Fission Track Thermochronology of Its Exposed Crystalline Basement

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 604
Author(s):  
Evgeny V. Vetrov ◽  
Johan De Grave ◽  
Natalia I. Vetrova ◽  
Fedor I. Zhimulev ◽  
Simon Nachtergaele ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Fission Track ◽  
Analytical Data ◽  
Tectonic Activity ◽  
Apatite Fission Track ◽  
Tectonic Processes ◽  
Basement Rocks ◽  
Fission Track Thermochronology ◽  
History Of ◽  
West Siberian Basin

The West Siberian Basin (WSB) is one of the largest intracratonic Meso-Cenozoic basins in the world. Its evolution has been studied over the recent decades; however, some fundamental questions regarding the tectonic evolution of the WSB remain unresolved or unconfirmed by analytical data. A complete understanding of the evolution of the WSB during the Mesozoic and Cenozoic eras requires insights into the cooling history of the basement rocks as determined by low-temperature thermochronometry. We presented an apatite fission track (AFT) thermochronology study on the exposed parts of the WSB basement in order to distinguish tectonic activation episodes in an absolute timeframe. AFT dating of thirteen basement samples mainly yielded Cretaceous cooling ages and mean track lengths varied between 12.8 and 14.5 μm. Thermal history modeling based on the AFT data demonstrates several Mesozoic and Cenozoic intracontinental tectonic reactivation episodes affected the WSB basement. We interpreted the episodes of tectonic activity accompanied by the WSB basement exhumation as a far-field effect from tectonic processes acting on the southern and eastern boundaries of Eurasia during the Mesozoic–Cenozoic eras.

scholarly journals Different Tectonic Evolution of Fast Cooling Ophiolite Mantles Recorded by Olivine-Spinel Geothermometry: Case Studies from Iballe (Albania) and Nea Roda (Greece)

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 64
Author(s):  
Micol Bussolesi ◽  
Giovanni Grieco ◽  
Alessandro Cavallo ◽  
Federica Zaccarini
Keyword(s):  
Tectonic Evolution ◽  
Early Stage ◽  
Mineral Chemistry ◽  
Northern Greece ◽  
Present Contribution ◽  
Cooling Rates ◽  
History Of ◽  
Ferrian Chromite ◽  
Fast Cooling ◽  
Subduction Setting

Mg-Fe2+ diffusion patterns in olivine and chromite are useful tools for the study of the thermal history of ultramafic massifs. In the present contribution, we applied the exponential modeling of diffusion patterns to geothermometry and geospeedometry of chromitite ores from two different ophiolite contexts. The Iballe ophiolite (Northern Albania) hosts several chromitite pods within dunites. Primary and re-equilibrated Mg#, estimated by using an exponential function, provided re-equilibration and primary temperatures ranging between 677 and 996 °C for chromitites and between 527 and 806 °C for dunites. Cooling rates for chromitites are higher than for dunites, suggesting a different genesis for the two lithologies, confirmed also by spinel mineral chemistry. Chromitites with MORB affinity formed in a SSZ setting at a proto-forearc early stage, explaining the higher cooling rates, while dunites, with boninitic affinity, were formed deeper in the mantle in a more mature subduction setting. At the Nea Roda ophiolite (Northern Greece) olivine in chromitites do not show Mg-Fe variations, and transformation into ferrian chromite produced “fake” diffusion patterns within chromite. The absence of diffusion patterns and the low estimated temperatures (550–656 °C) suggest that Nea Roda chromitites were completely re-equilibrated during an amphibolite-facies metamorphic event that obliterated all primary features.

scholarly journals Overview of Cordilleran oceanic terranes and their significance for the tectonic evolution of the northern Cordillera

2021 ◽  
Author(s):  
A Zagorevski ◽  
C R van Staal ◽  
J H Bédard ◽  
A Bogatu ◽  
D Canil ◽  
...  
Keyword(s):  
Continental Margin ◽  
Tectonic Evolution ◽  
Middle Triassic ◽  
Passive Margin ◽  
Suprasubduction Zone ◽  
Ophiolitic Rocks ◽  
Juvenile Crust ◽  
Tectonic Framework ◽  
Tectonic Reconstructions ◽  
Stratigraphic Nomenclature

Ophiolite complexes are an important component of oceanic terranes in the northern Cordillera and constitute a significant amount of juvenile crust added to the Mesozoic Laurentian continental margin during Cordilleran orogenesis. Despite their tectonic importance, few systematic studies of these complexes have been conducted. Detailed studies of the pseudostratigraphy, age, geochemistry, and structural setting of ophiolitic rocks in the northern Cordillera indicate that ophiolites formed in Permian to Middle Triassic suprasubduction zone settings and were obducted onto passive margin sequences. Re-evaluation of ophiolite complexes highlights fundamental gaps in the understanding of the tectonic framework of the northern Cordillera. The previous inclusion of ophiolite complexes into generic 'oceanic' terranes resulted in significant challenges for stratigraphic nomenclature, led to incorrect terrane definitions, and resulted in flawed tectonic reconstructions.

scholarly journals The geotectonic evolution of Olympus Mt and its mythological analogue

2017 ◽  
Vol 47 (2) ◽  
pp. 574
Author(s):  
I.D. Mariolakos ◽  
Ε. Manoutsoglou
Keyword(s):  
Tectonic Evolution ◽  
Modern World ◽  
High Mountain ◽  
Cultural Significance ◽  
Ancient Greek ◽  
Greek Religion ◽  
Know How ◽  
Tectonic Processes ◽  
Of Greece

Mt Olympus is the highest mountain of Greece (2918 m.) and one of the most important and well known locations of the modern world. This is related to its great cultural significance, since the ancient Greeks considered this mountain as the habitat of their Gods, ever since Zeus became the dominant figure of the ancient Greek religion and consequently the protagonist of the cultural regime. Before the generation of Zeus, Olympus was inhabited by the generation of Cronus. In this paper we shall refer to a lesser known mythological reference which, in our opinion, presents similarities to the geotectonic evolution of the wider area of Olympus. According to Apollodorus and other great authors, the God Poseidon and Iphimedia had twin sons, the Aloades, namely Otus and Ephialtes, who showed a tendency to gigantism. When they reached the age of nine, they were about 16 m. tall and 4.5 m. wide. Having then realized their powers, because of their gigantic proportions, they decided to climb Olympus and fight the Gods, exile Zeus and the others, and wed two Goddesses. Otus was to marry Hera and Ephialtes Artemis. But they did not know how to climb such a high mountain, so they decided to construct a “ladder”, by putting mount Ossa on top of mount Olympus and mount Pelion on top of Ossa. This description coincides with the geological and tectonic evolution of the wider Olympus area. But, these complex tectonic processes were completed about 8 – 10 m.a., i.e. millions of years before the appearance of humans, therefore it is impossible that these morphotectonic processes were witnessed by man, so the similarities between the myth of Aloades and the tectonic evolution of the area must be purely coincidental. But are they, or is there more here?

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