The Grenvillian assembly of Rodinia: Timing of accretion on the western margin of the Kalahari (Kaapvaal) Craton

2020 ◽  
Vol 123 (4) ◽  
pp. 441-464
Author(s):  
H.S. Van Niekerk ◽  
R. Armstrong ◽  
P. Vasconcelos
Keyword(s):  
Detrital Zircons ◽  
Age Dating ◽  
Granitic Gneiss ◽  
Detailed Model ◽  
Zircon Age ◽  
Western Margin ◽  
Tectonic History ◽  
Kalahari Craton ◽  
History Of ◽  
Shrimp Zircon

Abstract During the Grenvillian assembly of Rodinia, the Namaqua-Natal Metamorphic Province (NNMP) was formed as a result of the convergence of the Laurentia and Kalahari cratons. A detailed model for this accretion along the south-eastern margin of the Kalahari Craton has been established, but the tectonic history of the NNMP along the western margin of the Kalahari Craton has remained highly controversial. U-Pb SHRIMP zircon age dating of gneiss in the Kakamas Domain of the NNMP, as well as U-Pb SHRIMP age dating of detrital zircons and 40Ar/39Ar dating of metamorphic muscovite from sediments overlying the gneiss, confirms the presence of at least two separate events during the Namaqua-Natal Orogeny at ~1 166 Ma and 1 116 Ma. These events occurred after the Areachap Terrane was accreted onto the western margin of the Proto-Kalahari Craton during the Kheis Orogeny. 40Ar/39Ar ages derived from metamorphic muscovite formed in the metasediments of the Kheis terrane does not provide evidence for the timing of the Kheis Orogeny but suggests that it most likely only occurred after ~1 300 Ma and not at 1 800 Ma as commonly accepted. A U-Pb concordia age of ~1 166 Ma was derived from granitic gneiss in the Kakamas Domain of the Bushmanland Subprovince, possibly reflecting subduction and the initiation of continent-continent collision between the Proto-Kalahari Craton and the Bushmanland Subprovince. This granitic gneiss is nonconformably overlain by the metasediments of the Korannaland Group that contains metamorphic muscovite with 40Ar/39Ar ages of ~1 116 Ma. This age suggest that complete closure of the ocean between the Proto-Kalahari Craton and Bushmanland Subprovince probably occurred about 50 Ma after the intrusion of the ~1 166 Ma granitic gneisses.

Obducted nappe sequence in the San Juan Islands – northwest Cascades thrust system, Washington and British Columbia

2012 ◽  
Vol 49 (7) ◽  
pp. 796-817 ◽  
Author(s):  
E.H. Brown
Keyword(s):  
British Columbia ◽  
Detrital Zircons ◽  
San Juan ◽  
San Juan Islands ◽  
Tectonic History ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
History Of ◽  
Accreted Terranes ◽  
Thrust System

The San Juan Islands – northwest Cascades thrust system in Washington and British Columbia is composed of previously accreted terranes now assembled as four broadly defined composite nappes stacked on a continental footwall of Wrangellia and the Coast Plutonic Complex. Emplacement ages of the nappe sequence are interpreted from zircon ages, field relations, and lithlogies, to young upward. The basal nappe was emplaced prior to early Turonian time (∼93 Ma), indicated by the occurrence of age-distinctive zircons from this nappe in the Sidney Island Formation of the Nanaimo Group. The emplacement age of the highest nappe in the thrust system postdates 87 Ma detrital zircons within the nappe. The nappes bear high-pressure – low-temperature (HP–LT) mineral assemblages indicative of deep burial in a thrust wedge; however, several features indicate that metamorphism occurred prior to nappe assembly: metamorphic discontinuities at nappe boundaries, absence of HP–LT assemblages in the footwall to the nappe pile, and absence of significant unroofing detritus in the Nanaimo Group. A synorogenic relationship of the thrust system to the Nanaimo Group is evident from mutually overlapping ages and by conglomerates of Nanaimo affinity that lie within the nappe pile. From the foregoing relations, and broader Cordilleran geology, the tectonic history of the nappe terranes is interpreted to involve initial accretion and subduction-zone metamorphism south of the present locality, uplift and exhumation, orogen-parallel northward transport of the nappes as part of a forearc sliver, and finally obduction at the present site over the truncated south end of Wrangellia and the Coast Plutonic Complex.

A distant magmatic source for Cretaceous karst bauxites of Southern Apennines (Italy), revealed through SHRIMP zircon age dating

Terra Nova ◽  
2012 ◽  
Vol 24 (4) ◽  
pp. 326-332 ◽  
Author(s):  
Maria Boni ◽  
Steven M. Reddy ◽  
Nicola Mondillo ◽  
Giuseppina Balassone ◽  
Rich Taylor
Keyword(s):  
Age Dating ◽  
Southern Apennines ◽  
Zircon Age ◽  
Magmatic Source ◽  
Shrimp Zircon

Grenvillian provenance for the amphibolite-grade Trap Falls Formation: implications for early Paleozoic tectonic history of New England

1997 ◽  
Vol 34 (9) ◽  
pp. 1286-1294 ◽  
Author(s):  
D. K. McDaniel ◽  
G. N. Hanson ◽  
S. M. McLennan ◽  
J. H. Sevigny
Keyword(s):  
New England ◽  
Detrital Zircons ◽  
Tectonic History ◽  
Chemical Index ◽  
Depleted Mantle ◽  
Isotopic Analyses ◽  
History Of ◽  
Chemical Index Of Alteration ◽  
Depositional Age ◽  
Ree Patterns

The Trap Falls Formation is a sequence of interlayered quartzites and schists that crops out in the Appalachian belt in southern Connecticut, and was deformed and metamorphosed to middle amphibolite grade during Acadian orogenesis. Schists have high Al2O3 and low CaO, Na2O, and K2O (chemical index of alteration CIA = 68–70), consistent with a significant weathering history in the sediment source. Rare earth element (REE) patterns for both schists and quartzites parallel post-Archean average Australian Shale, with light REE enrichment and well-developed Eu anomalies, suggesting an average upper crustal source. Whole-rock Nd and Pb isotopic analyses indicate old sources, with depleted mantle model ages (TDM) from 1880 to 1660 Ma, 207Pb/204Pb from 15.62 to 15.87, and 206Pb/204Pb from 19.11 to 22.08. U–Pb ages for single-grain and multigrain populations of detrital zircons range between 1113 and 992 Ma, the youngest of which defines a maximum depositional age for the Trap Falls Formation. U–Pb zircon ages indicate a late Grenvillian source for the zircons. Nd and Pb isotopic compositions are consistent with a source that is dominated by Grenville-age rocks with some component of older crust. Combining all of the data, we interpret that the protolith of the Trap Falls Formation was comprised of aluminous muds interbedded with clean quartz arenites, and suggest that they were deposited on the stable, trailing-edge margin of North America sometime during the Late Proterozoic to the Early Cambrian. The sediments were derived from a weathered source with an upper continental crust composition. Isotopic data and zircon ages indicate that this source was dominated by Grenville-age rocks.

scholarly journals Mineralogy, Geochemistry, and Age Constraints on the Axinite-Bearing Gukjeon Pb–Zn Skarn Deposit in the Miryang Area, South Korea

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 619
Author(s):  
Namhoon Kim ◽  
Sang-Mo Koh ◽  
Byoung-Woon You ◽  
Bum-Han Lee
Keyword(s):  
Age Dating ◽  
Southeastern Part ◽  
Zircon Age ◽  
Fine Grained ◽  
Magmatic Rocks ◽  
Temporal Relationships ◽  
The Pacific ◽  
Back Arc ◽  
Age Constraints ◽  
Shrimp Zircon

The axinite-bearing Gukjeon Pb–Zn deposit is hosted by the limestone, a member of the Jeonggaksan Formation, which, in turn, forms the part of the Jusasan subgroup of the Yucheon Group in the Gyeongsang Basin in the southeastern part of the Korean Peninsula. In this study, we attempted to interpret the spatial and temporal relationships among geologic events, including the mineralization of this deposit. We constructed a new 3D orebody model and suggested a relationship between skarn alteration and related mineralization. Mineralization timing was constrained using SHRIMP zircon age dating results combined with boron geochemistry on coeval intrusive rocks. Skarn alterations are restrictively found in several horizons of the limestone formation. The major skarn minerals are garnet (grossular), pyroxene (hedenbergite), amphibole (actinolite and ferro-actinolite), axinite (tizenite and ferro-axinite), and epidote (clinozoisite and epidote). The three stages of pre-skarn, syn-skarn, and post-skarn alteration are recognized within the deposit. The syn-skarn alteration is characterized by prograde metasomatic pyroxene and garnet, and the retrograde metasomatic amphibole, axinite, and epidote. Major skarn sulfide minerals are sphalerite, chalcopyrite, galena, and pyrite, which were predominantly precipitated during the retrograde stage and formed amphibole and axinite skarns. The skarn orebodies seem to be disc- or flat-shaped with a convex form at the central part of the orebodies. The vertical ascending and horizontal infiltration of boron-rich hydrothermal fluid probably controlled the geometry of the orebodies. Considering the whole-rock major, trace, and boron geochemical and geochronological results, the timing of Pb–Zn mineralization can be tightly constrained between the emplacement of boron-poor intrusion (fine-grained granodiorite, 82.8 Ma) and boron-rich intrusion (porphyritic andesite in Beomdori andesitic rocks, 83.8 Ma) in a back-arc basin setting. The boron for mineralization was sourced from late Cretaceous (Campanian), subduction-related magmatic rocks along the margin of the Pacific plate.

scholarly journals U–Pb zircon age dating of diamond-bearing gneiss from Fjørtoft reveals repeated burial of the Baltoscandian margin during the Caledonian Orogeny

2019 ◽  
Vol 156 (11) ◽  
pp. 1949-1964 ◽  
Author(s):  
Katarzyna Walczak ◽  
Simon Cuthbert ◽  
Ellen Kooijman ◽  
Jarosław Majka ◽  
Matthijs A. Smit
Keyword(s):  
Detrital Zircon ◽  
Age Dating ◽  
Western Gneiss Region ◽  
Zircon Age ◽  
Metasedimentary Rocks ◽  
Ultra High Pressure ◽  
Metamorphic History ◽  
History Of ◽  
Caledonian Orogeny ◽  
Late Neoproterozoic

AbstractThe first find of microdiamond in the Nordøyane ultra-high-pressure (UHP) domain of the Western Gneiss Region (WGR) of the Scandinavian Caledonides reshaped tectonic models for the region. Nevertheless, in spite of much progress regarding the meaning and significance of this find, the history of rock that the diamonds were found in is complex and still largely ambiguous. To investigate this, we report U–Pb zircon ages obtained from the exact crushed sample material in which metamorphic diamond was first found. The grains exhibit complicated internal zoning with distinct detrital cores overgrown by metamorphic rims. The cores yielded a range of ages from the Archaean to the late Neoproterozoic / early Cambrian. This detrital zircon age spectrum is broadly similar to detrital signatures recorded by metasedimentary rocks of the Lower and Middle allochthons elsewhere within the orogen. Thus, our dating results support the previously proposed affinity of the studied gneiss to the Seve–Blåhø Nappe of the Middle Allochthon. Metamorphic rims yielded a well-defined peak at 447 ± 2 Ma and a broad population that ranges between c. 437 and 423 Ma. The data reveal a prolonged metamorphic history of the Fjørtoft gneiss that is far more complex then would be expected for a UHP rock that has seen a single burial and exhumation cycle. The data are consistent with a model involving multiple such cycles, which would provide renewed support for the dunk tectonics model that has been postulated for the region.

Detrital zircon U-Pb ages and whole-rock geochemistry of early Paleozoic metasedimentary rocks in the Mongolian Altai: Insights into the tectonic affinity of the whole Altai-Mongolian terrane

2019 ◽  
Vol 132 (3-4) ◽  
pp. 477-494
Author(s):  
Xiaoping Long ◽  
Jin Luo ◽  
Min Sun ◽  
Xuan-ce Wang ◽  
Yujing Wang ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Age Distribution ◽  
Isotopic Analysis ◽  
Detrital Zircons ◽  
Cumulative Distribution ◽  
Early Paleozoic ◽  
Zircon Age ◽  
Western Margin ◽  
Metasedimentary Rocks ◽  
Mongolian Altai

Abstract The tectonic affinity of the terranes and microcontinents within the Central Asian Orogenic Belt (CAOB) remains controversial. The Altai-Mongolian terrane (AMT), as a representative tectonic unit in the Mongolian collage, plays a vital role in reconstructing evolution history of the CAOB. The well-preserved early Paleozoic sedimentary sequence covering in this terrane could be considered as a fingerprint to track its provenance and tectonic affinity. Here, we present new whole-rock geochemistry, detrital zircon U-Pb dating, and Hf isotopic analysis for the metasedimentary rocks from the Mongolian Altai in order to shed new light on the tectonic affinity of the AMT. The youngest detrital zircon ages and the regional intrusions constrain the depositional time of the Mongolian Altai sequence to between Late Silurian and Early Devonian, which is consistent with the Habahe group in the western Chinese Altai. The features of whole-rock geochemistry and the cumulative distribution curves of the detrital zircon age spectra indicate that the Mongolian Altai sequence was probably deposited in an active continental setting during early Paleozoic. The zircon age spectra of our samples are all characterized by a main age group in the early Cambrian (peak at 541 Ma, 522 Ma, 506 Ma and 496 Ma, respectively), subdominant age populations during the Tonian, as well as rare older zircons. The nearby Lake Zone of Ikh-Mongol Arc most likely provided plenty of early Paleozoic materials, the subdominant Neoproterozoic detrital zircons could be supplied by the felsic intrusions along the western margin of the Tuva-Mongol microcontinent, and the sparse older zircons may be derived from its basement material. The Precambrian age distribution of the AMT is quite similar to both the Tarim and Siberia cratons, but the Siberia Craton displays a closer resemblance in Hf isotopic composition with the AMT. Thus, we believe that the Siberia Craton contains a closer tectonic affinity with the AMT, and that the Tuva-Mongol microcontinent possibly rifted from the western margin of this craton after the Tonian. To the south of the AMT, recent studies indicated the Yili and Central Tianshan blocks in the Kazakhstan collage of the western CAOB likely have a closer affinity with Gondwana. Therefore, the microcontinents in the CAOB most likely derived bilaterally from both the Siberia Craton and the Gondwana supercontinent. Moreover, our Hf isotopic compositions indicate two significant continental growth events in the Tonian and early Paleozoic, respectively.

scholarly journals Neoarchean tectonic history of the Teton Range: Record of accretion against the present-day western margin of the Wyoming Province

Geosphere ◽  
2018 ◽  
Vol 14 (3) ◽  
pp. 1008-1030 ◽  
Author(s):  
B. Ronald Frost ◽  
Susan M. Swapp ◽  
Carol D. Frost ◽  
Davin A. Bagdonas ◽  
Kevin R. Chamberlain
Keyword(s):  
Western Margin ◽  
Tectonic History ◽  
History Of ◽  
Teton Range ◽  
Wyoming Province

scholarly journals SHRIMP U–Pb zircon evidence for age, provenance, and tectonic history of early Paleozoic Ganderian rocks, east-central Maine, USA

2018 ◽  
pp. 335-387
Author(s):  
Allan Ludman ◽  
John Aleinikoff ◽  
Henry N. Berry IV ◽  
John T. Hopeck
Keyword(s):  
Foreland Basin ◽  
Volcanic Eruptions ◽  
Detrital Zircons ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Tectonic History ◽  
Late Cambrian ◽  
Quartz Arenite ◽  
History Of ◽  
Host Rocks

SHRIMP U–Pb zircon ages from Ganderia in eastern Maine clarify the ages and provenance of basement units in the Miramichi and St. Croix terranes and of cover rocks in the Fredericton trough and Central Maine/Aroostook-Matapedia basin (CMAM). These new data constrain timing of orogenic events and help understand the origin of the cover rock depocenters.Detrital zircon data generally confirm suggested ages of the formations sampled. Zircon grains with ages of ca. 430 Ma in both depocenters, only slightly older than their host rocks, were probably derived from the earliest volcanic eruptions in the Eastport-Mascarene belt. Their presence indicates that unnamed CMAM sandstone units may be as young as Pridoli and their absence from the Appleton Ridge and Digdeguash formations suggests that these formations are older than initial Eastport-Mascarene volcanism. Detrital and volcanic zircon ages confirm a Late Cambrian to Middle Ordovician age for the Miramichi succession and date Miramichi volcanism at 469.3 ± 4.6 Ma. In the St. Croix terrane, zircon grain with an age of 477.4 ± 3.7 Ma from an ashfall at the base of the Kendall Mountain Formation and age spectra and fossils from overlying quartz arenite suggest that the formation may span Floian to Sandbian time. The main source of CMAM and Fredericton sediment was recycled Ganderian basement from terranes emergent after Late Ordovician orogenesis, supplemented by Silurian tephra. Zircon barcodes and lithofacies and tectonic models suggest little, if any, input from Laurentia or Avalonia.Zircon- and fossil-based ages indicate coeval Upper Ordovician deformation in the St. Croix (ca. 453 to 442 Ma) and Miramichi (ca. 453 to 446 Ma) terranes. Salinic folding in the southeastern Fredericton trough is bracketed between the 421.9 ± 2.4 Ma age of the Pocomoonshine gabbro-diorite and 430 Ma detrital zircons in the Flume Ridge Formation. Zircon ages, lithofacies analysis, and paleontological evidence support the origin of the Fredericton trough as a Salinic foredeep. The CMAM basin cannot have been an Acadian foreland basin, as sedimentation began millions of years before Acadian subduction.

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