The Tonian supercontinent Rodinia is hypothesized to have included almost all Proterozoic continental blocks. Competing models variably place South China at the core or periphery of Rodinia or separated from it entirely. Tonian paleogeographic models also vary in whether they incorporate hypothesized large and rapid oscillatory true polar wander associated with the ca. 810–795 Ma Bitter Springs Stage. Here, we present paleomagnetic data paired with U‐Pb chemical abrasion isotope dilution thermal ionization mass spectrometry zircon geochronology from the Tonian Xiajiang Group in South China to establish the craton's position and test the Bitter Springs Stage true polar wander hypothesis. Fine‐grained siliciclastic sediments and ashes of the Xiajiang Group post‐date the Jiangnan Orogeny, which united the Yangtze and Cathaysia blocks. A U‐Pb zircon date of 815.73 ± 0.18 Ma from a tuff near the base of the Xiajiang Group constrains the Jiangnan Orogeny to have ended between ca. 830 and 816 Ma. The paleomagnetic and geochronologic data constrain South China to high latitudes ca. 813 Ma and indicate a relatively stable high‐latitude position from ca. 821 to 805 Ma. These high‐latitude constraints either connect the craton to Rodinia along its periphery or disconnect it from the supercontinent entirely. The difference in pole position between the pre‐Bitter Springs Stage Xiajiang Group pole and the syn‐Bitter Springs Stage Madiyi Formation pole is significantly less than that predicted for the Bitter Springs Stage true polar wander hypothesis. If this pole difference is interpreted as true polar wander superimposed upon differential plate motion, it requires South China to have been separate from Rodinia.
The
- NSF-PAR ID:
- 10387608
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Tectonics
- Volume:
- 40
- Issue:
- 5
- ISSN:
- 0278-7407
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The occurrence of plate tectonic processes on Earth during the Paleoproterozoic is supported by ca. 2.2–1.8 Ga subduction‐collision orogens associated with the assembly of the Columbia‐Nuna supercontinent. Subsequent supercontinent breakup is evidence by global ca. 1.8–1.6 Ga large igneous provinces. The North China craton is notable for containing Paleoproterozoic orogens along its margins, herein named the Northern Margin orogen, yet the nature and timing of orogenic and extensional processes of these orogens and their role in the supercontinent cycle remain unclear. In this contribution, we present new field observations, U‐Pb zircon and baddeleyite geochronology dates, and major/trace‐element and isotope geochemical analyses from the northern margin of the North China craton that detail its Paleoproterozoic tectonic and magmatic history. Specifically, we record the occurrence of ca. 2.2–2.0 Ga magmatic arc rocks, ca. 1.9–1.88 Ga tectonic mélange and mylonitic shear zones, and folded lower Paleoproterozoic strata. These rocks were affected by ca. 1.9–1.8 Ga granulite‐facies metamorphism and ca. 1.87–1.78 Ga post‐collisional, extension‐related magmatism along the cratonal northern margin. We interpret that the generation and emplacement of these rocks, and the coupled metamorphic and magmatic processes, were related to oceanic subduction and subsequent continent‐continent collision during the Paleoproterozoic. The occurrence of ca. 1.77–1.73 Ga mafic dykes and ca. 1.75 Ga mylonitic shear zones along the northern margin of the North China craton may have been related to a regional mantle plume event. Our results are consistent with modern style plate tectonics, including oceanic subduction‐related plate convergence and continent‐continent collision, operating in the Paleoproterozoic.
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