Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: Characteristics, extent, and tectonic significance

2014 ◽  
Vol 126 (7-8) ◽  
pp. 990-1015 ◽  
Author(s):  
J. Tull ◽  
C. S. Holm-Denoma ◽  
C. I. Barineau
Keyword(s):  
Blue Ridge ◽  
Middle Ordovician ◽  
Southern Appalachian ◽  
Tectonic Significance ◽  
Back Arc

scholarly journals Provenance and tectonic significance of the Zhongwunongshan Group from the Zhongwunongshan Structural Belt in China: insights from zircon geochronology

2020 ◽  
Vol 12 (1) ◽  
pp. 25-43
Author(s):  
Yuan Peng ◽  
Yongsheng Zhang ◽  
Eenyuan Xing ◽  
Linlin Wang
Keyword(s):  
Detrital Zircon ◽  
Sedimentary Basin ◽  
Early Paleozoic ◽  
Granitic Gneiss ◽  
Metamorphic Belt ◽  
Early Devonian ◽  
Tectonic Environment ◽  
Tectonic Significance ◽  
North Qaidam ◽  
Back Arc

AbstractThe Zhongwunongshan Structural Belt (ZWSB) locates between the Olongbruk Microblock of North Qaidam and the South Qilian Block in China, and it has important implication for understanding the tectonic significance of North Qaidam. Nowadays, there are few discussion on the Caledonian tectonothermal events of the Zhongwunongshan Structural Belt, and there exist different opinions on provenance and tectonic environment of the Zhongwunongshan Group in the ZWSB and its adjacent North Qaidam. In this study, a comprehensive analysis of the detrital zircon geochronological research was carried out on the Zhongwunongshan Group. The detrital zircon U-Pb dating results showed two major populations. The first was Neoproterozoic (966-725 Ma) with a ∈Hf(t) = −15.9 to 9.5, and the other was late Early Paleozoic (460-434Ma) with a ∈Hf(t) = −9.6 to −3.1. In combination with previous research, the dominated provenances were found to be the Neoproterozoic granitic gneiss of the Yuqia-Shaliuhe HP-UHP metamorphic belt and the late Early Paleozoic granite of the Tanjianshan ophiolite-volcanic arc belt in North Qaidam. The Zhongwunongshan Group was deposited in the back-arc sedimentary basin related to the Caledonian collisional orogeny during Middle Silurian-Early Devonian (434-407.9 Ma).

scholarly journals Petrogenesis and Tectonic Significance of the ~276 Ma Baixintan Ni-Cu Ore-Bearing Mafic-Ultramafic Intrusion in the Eastern Tianshan Orogenic Belt, NW China

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 348
Author(s):  
Minxin You ◽  
Wenyuan Li ◽  
Houmin Li ◽  
Zhaowei Zhang ◽  
Xin Li
Keyword(s):  
Orogenic Belt ◽  
Olivine Gabbro ◽  
Early Permian ◽  
Eastern Tianshan ◽  
Nw China ◽  
Tianshan Orogenic Belt ◽  
Tectonic Significance ◽  
Ultramafic Intrusion ◽  
Back Arc ◽  
Duke Island

The Baixintan mafic-ultramafic intrusion in the Dananhu-Tousuquan arc of the Eastern Tianshan orogenic belt is composed of lherzolite, olivine gabbro, and gabbro. Olivine gabbros contain zircon grains with a U-Pb age of 276.8 ± 1.1 Ma, similar to the ages of other Early Permian Ni-Cu ore-bearing intrusions in the region. The alkaline-silica diagrams, AFM diagram, together with the Ni/Cu-Pd/Ir diagram, indicate that the parental magmas for the Baixintan intrusion were likely high-Mg tholeiitic basaltic in composition. The Cu/Pd ratios, the relatively depleted PGEs and the correlations between them demonstrate that the parental magmas had already experienced sulfide segregation. The lower CaO content in pyroxenites compared with the Duke Island Alaskan-type intrusion and the composition of spinels imply that Baixintan is not an Alaskan-type intrusion. By comparing the Baixintan intrusion with other specific mafic-ultramafic intrusions, this paper considers that the mantle source of the Baixintan intrusion is metasomatized by subduction slab-derived fluids’ components, which gives rise to the negative anomalies of Nb, Ti, and Ta elements. Nb/Yb-Th/Yb, Nb/Yb-TiO2/Yb, and ThN-NbN plots show that the Baixintan intrusion was emplaced in a back-arc spreading environment and may be related to a mantle plume.

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

2021 ◽  
Vol 57 ◽  
pp. 239-273
Author(s):  
Allan Ludman ◽  
Christopher McFarlane ◽  
Amber T.H. Whittaker
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
East Central ◽  
Arc Volcanism ◽  
Middle Ordovician ◽  
Volcanic Suite ◽  
Back Arc

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This >150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

The tectonic significance of Ordovician basic igneous rocks in the Southern Uplands, southwest Scotland

1995 ◽  
Vol 132 (5) ◽  
pp. 549-556 ◽  
Author(s):  
E. R. Phillips ◽  
R. P. Barnes ◽  
R. J. Merriman ◽  
J. D. Floyd
Keyword(s):  
Volcanic Rocks ◽  
Accretionary Prism ◽  
Igneous Rocks ◽  
Geochemical Data ◽  
Published Data ◽  
Volcanic Material ◽  
Tectonic Significance ◽  
Arc Setting ◽  
Back Arc ◽  
Midocean Ridge

AbstractIn the northern part of the Southern Uplands, restricted volumes of basic igneous rocks occur at or near the base of the Ordovician sedimentary strata. These rocks have previously been interpreted as ocean-floor tholeiites representative of the subducted Iapetus oceanic plate, preserved as tectonic slivers in a fore-arc accretionary prism. The alternative, back-arc basin model proposed for the Southern Uplands on sedimentological evidence raises questions over the origin of these rocks. New geochemical data and previously published data clearly indicate that the volcanic material does not have a simple single source. The oldest (Arenig) volcanic rocks from the Moffat Shale Group associated with the Leadhills Fault include alkaline within-plate basalts and tholeiitic lavas which possibly display geochemical characteristics of midocean ridge basalts. In the northernmost occurrence, alkaline and tholeiitic basalts contained within the Caradoc Marchburn Formation are both of within-plate ocean island affinity. To the south, in the Gabsnout Burn area, the Moffat Shale Group contains lenticular bodies of dolerite and basalt which have characteristics of island-arc to transitional basalts. This complex association of basaltic volcanic rocks is, at the present time, difficult to reconcile with either a simple fore-arc or back-arc setting for the Southern Uplands. However, the increasing arc-related chemical influence on basic rock geochemistry towards the southeast may tentatively be used in support of a southern arc-terrane, and as a result, a back-arc situation for the Southern Uplands basin. An alternative is that these volcanic rocks may represent the local basement to the basin and include remnants of an arc precursor to the Southern Uplands basin.

Late Quaternary Landscape Evolution at Flat Laurel Gap, Blue Ridge Mountains, North Carolina

1988 ◽  
Vol 30 (1) ◽  
pp. 7-11 ◽  
Author(s):  
David S. Shafer
Keyword(s):  
North Carolina ◽  
Landscape Evolution ◽  
Late Quaternary ◽  
Appalachian Mountains ◽  
Blue Ridge ◽  
Blue Ridge Mountains ◽  
Southern Appalachian ◽  
Organic Sediment ◽  
Absolute Age ◽  
Age Determinations

Analysis of colluvial, fluvial, and bog sediments at Flat Laurel Gap (1500 m) in the Blue Ridge Mountains of North Carolina provides a record of late Quaternary landscape evolution. Thermoluminescence (TL) analysis provides the first absolute-age determinations available for presumed periglacial deposits in the southern Appalachian Mountains. The Pleistocene/Holocene transition, dated between 11,900 and 10,100 yr B.P., represents a period of climatic amelioration and a change from colluvial to alluvial processes. A TL date of 7400 ± 1000 yr B.P. for matrix within a block-stream indicates possible early Holocene reworking of Pleistocene periglacial colluvium. Organic sediment deposition in a bog that began about 3400 yr B.P. increased in rate from 0.02 to 0.09 cm/yr with the onset of logging and land clearance about 1880 A.D.

Evolution of the Murphy synclinorium, southern Appalachian Blue Ridge, USA

2012 ◽  
Vol 44 ◽  
pp. 151-166 ◽  
Author(s):  
James F. Tull ◽  
Haitham Baggazi ◽  
Mark S. Groszos
Keyword(s):  
Blue Ridge ◽  
Southern Appalachian

New paleontological evidence for complex middle Paleozoic tectonic evolution in the Appalachian western Blue Ridge

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2105-2118
Author(s):  
Mary E. Lupo ◽  
James F. Tull ◽  
John Repetski ◽  
Paul A. Mueller
Keyword(s):  
North Carolina ◽  
Tectonic Evolution ◽  
Blue Ridge ◽  
Relative Paucity ◽  
Southern Appalachian ◽  
Stratigraphic Framework ◽  
Taconic Orogeny ◽  
Middle Paleozoic ◽  
Thrust Sheets ◽  
Group B

Abstract Reconstructing the tectonic evolution of the southern Appalachian metamorphic internides is hampered by the relative paucity of accurate geochronologic constraints and the apparent rarity or absence of Paleozoic cover sequences. At the orogen’s greatest width, near the junction of Georgia, North Carolina, and Tennessee, the western Blue Ridge is a composite metamorphic allochthon of three major thrust sheets: (A) a basal sheet above the Great Smoky fault overlying rocks of the foreland thrust belt composed of the Lower Cambrian Chilhowee Group and underlying Sandsuck Formation of the Neoproterozoic Walden Creek Group; (B) an intermediate sheet above the Maggies Mill–Citico fault composed of the middle Paleozoic Maggies Mill Formation; and (C) the main mass of the western Blue Ridge above the Alaculsy Valley–Miller Cove fault composed of the Neoproterozoic Ocoee Supergroup, and younger overlying sequences in the Epperson and Murphy synclinoria. The age of peak deformation and metamorphism in all of these sequences has historically been assigned to the Ordovician Taconic orogeny, but recent paleontologic discoveries suggest these events are significantly younger. In addition to the middle Paleozoic fauna recently reported from the Maggies Mill Formation in the intermediate thrust sheet, Silurian-Devonian conodonts have been found in units formerly correlated with the Walden Creek Group in the Epperson synclinorium. These discoveries suggest that widespread middle Paleozoic successor basin sequences unconformably overlie the Neoproterozoic-Cambrian drift-facies of the Chilhowee Group (and equivalents) and underlying rift-facies of the Ocoee Supergroup, and require modifications to existing models for the timing of the region’s stratigraphic framework and tectono-metamorphic evolution.

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