Early Paleozoic rifting and reactivation of a passive-margin rift: Insights from detrital zircon provenance signatures of the Potsdam Group, Ottawa graben: Comment

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).

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The initiation of the early Paleozoic Cordilleran miogeocline: evidence from the uppermost Proterozoic – Lower Cambrian Hamill Group of southeastern British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e88-001 ◽

1988 ◽

Vol 25 (1) ◽

pp. 1-19 ◽

Cited By ~ 45

Author(s):

William J. Devlin ◽

Gerard C. Bond

Keyword(s):

British Columbia ◽

Lower Cambrian ◽

Direct Evidence ◽

Thermal Anomaly ◽

Passive Margin ◽

Early Paleozoic ◽

Upper Proterozoic ◽

Windermere Supergroup ◽

Depositional Setting ◽

Thermal Subsidence

The uppermost Proterozoic–Lower Cambrian Hamill Group of southeastern British Columbia contains geologic evidence for a phase of extensional tectonism that led directly to the onset of thermally controlled subsidence in the Cordilleran miogeocline. Moreover, the Hamill Group contains the sedimentological record of the passage of the ancient passive margin from unstable tectonic conditions associated with rifting and (or) the earliest phases of thermal subsidence to post-rift conditions characterized by stabilization of the margin and dissipation of the thermal anomaly generated during the rift phase (the rift to post-rift transition). Widespread uplift that occurred prior to and during the deposition of the lower Hamill Group is indicated by an unconformable relation with the underlying Windermere Supergroup and by stratigraphic relations between Middle and Upper Proterozoic strata and unconformably overlying upper Lower Cambrian quartz arenites (upper Hamill Group) in the southern borderlands of the Hamill basin. In addition, the coarse grain size, the feldspar content, the depositional setting, and the inferred provenance of the lower Hamill Group are all indicative of the activation of basement sources along the margins of the Hamill basin. Geologic relations within the Hamill Group that provide direct evidence for extensional tectonism include the occurrence of thick sequences of mafic metavolcanics and rapid vertical facies changes that are suggestive of syndepositional tectonism.Evidence of extensional tectonism in the Hamill Group directly supports inferences derived from tectonic subsidence analyses that indicate the rift phase that immediately preceded early Paleozoic post-rift cooling could not have occurred more than 10–20 Ma prior to 575 ± 25 Ma. These data, together with recently reported isotopic data that suggest deposition of the Windermere Supergroup began ~730–770 Ma, indicate that the rift-like deposits of the Windermere Supergroup are too old to represent the rifting that led directly to the deposition of the Cambro-Ordovician post-rift strata. Instead, Windermere sedimentation was apparently initiated by an earlier rift event, probably of regional extent, that was part of a protracted, episodic rift history that culminated with continental breakup in the latest Proterozoic – Early Cambrian.

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ROLE OF THERMAL SUBSIDENCE, FLEXURE, AND EUSTASY IN THE EVOLUTION OF EARLY PALEOZOIC PASSIVE-MARGIN CARBONATE PLATFORMS

Controls on Carbonate Platforms and Basin Development ◽

10.2110/pec.89.44.0039 ◽

1989 ◽

pp. 39-61 ◽

Cited By ~ 24

Author(s):

GERARD C. BOND ◽

MICHELLE A. KOMINZ ◽

MICHAEL S. STECKLER ◽

JOHN P. GROTZINGER

Keyword(s):

Passive Margin ◽

Early Paleozoic ◽

Carbonate Platforms ◽

Thermal Subsidence

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Pairwise sample comparisons and multidimensional scaling of detrital zircon ages with examples from the North American platform, basin, and passive margin settings

Lithosphere ◽

10.1130/l700.1 ◽

2018 ◽

Vol 10 (3) ◽

pp. 478-491 ◽

Cited By ~ 15

Author(s):

Gregory K. Wissink ◽

Bruce H. Wilkinson ◽

Gregory D. Hoke

Keyword(s):

Multidimensional Scaling ◽

North American ◽

Detrital Zircon ◽

Passive Margin ◽

The North ◽

Detrital Zircon Ages

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Volcanism on the passive margin of Laurentia: an early Paleozoic analogue of Cretaceous volcanism on the northeastern American margin: Reply

Canadian Journal of Earth Sciences ◽

10.1139/e90-166 ◽

1990 ◽

Vol 27 (11) ◽

pp. 1552-1554 ◽

Cited By ~ 1

Author(s):

Stephen Kumarapeli ◽

Karen St. Seymour ◽

Hillar Pintson ◽

Elizabeth Hasselgren

Keyword(s):

Passive Margin ◽

Early Paleozoic ◽

Cretaceous Volcanism

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Insights into Polyphase Phanerozoic Tectonic Events in SE China: Integrated Isotopic Microanalysis of Detrital Zircon and Monazite

Lithosphere ◽

10.2113/2020/8837978 ◽

2020 ◽

Vol 2020 (1) ◽

pp. 1-17

Author(s):

Li-Guang Wu ◽

Xian-Hua Li ◽

Weihua Yao ◽

Xiao-Xiao Ling ◽

Kai Lu

Keyword(s):

Detrital Zircon ◽

Beach Sand ◽

Sand Sample ◽

Early Paleozoic ◽

Isotopic Study ◽

Tectonic Events ◽

Crustal Reworking ◽

Detrital Zircon Ages ◽

Age Range ◽

Se China

Abstract Widespread Paleozoic and Mesozoic granites are characteristics of SE China, but the geodynamic mechanisms responsible for their emplacement are an issue of ongoing debate. To shed new light on this issue, we present an integrated geochronological and isotopic study of detrital zircon and monazite from Cambrian metasandstones and modern beach sands in the Yangjiang region, SE China. For the Cambrian metasandstone sample, detrital zircon displays a wide age range between 490 and 3000 Ma, while monazite grains record a single age peak of 235 Ma. The results suggest that a significant Triassic (235 Ma) metamorphic event is recorded by monazite but not zircon. For the beach sand sample, detrital zircon ages show six peaks at ca. 440, 240, 155, 135, 115, and 100 Ma, whereas detrital monazite yields a dominant age peak at 237 Ma and a very minor age peak at 435 Ma. Beach sand zircon displays features that are typical of a magmatic origin. Their Hf–O isotopes reveal two crustal reworking events during the early Paleozoic and Triassic, in addition to one juvenile crustal growth event during the Jurassic–Cretaceous. The beach sand monazite records intense Triassic igneous and metamorphic events with significant crustal reworking. Such early Paleozoic and Triassic geochemical signatures of detrital zircon and monazite suggest they were derived from granitoids and metamorphic rocks which formed in intraplate orogenies, i.e., the early Paleozoic Wuyi–Yunkai Orogeny and Triassic Indosinian Orogeny. The Jurassic–Cretaceous signature of detrital zircon may reflect multistage magmatism that was related to subduction of the Paleo-Pacific Plate beneath SE China.

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