The history of the South China Craton and the constituent Yangtze and Cathaysia blocks are directly linked to Earth's Phanerozoic and Precambrian record of supercontinent assembly and dispersal. ...Exposed Archean rocks are limited to isolated fragments in the Yangtze Block that preserve a record of Meso- to Neo-Archean magmatism, sedimentation and metamorphism associated with a period of global craton formation and stabilization that corresponds with the assembly of the Kenor supercontinent/supercraton. However, there are insufficient data to link its history with other similar aged cratons. The tectonostratigraphic record in South China in the Paleoproterozoic, corresponding with the assembly of Nuna, suggests that rock units in the Yangtze Block were spatially linked with northwestern Laurentia and possibly Siberia, whereas Cathaysia was joined to northern India. During the formation of Rodinia at the end of the Mesoproterozoic through to that of Pangea in the mid-Paleozoic, Cathaysia remained joined to northern India. Early Neoproterozoic supra-subduction zone magmatic arc-back arc assemblages ranging in age from ~1000Ma to 810Ma occur within Cathaysia, along its northwestern margin, and along the southeastern margin of the Yangtze Block. These rocks provide a record of convergent plate interaction, which continued along the western margin of the Yangtze Block until around 700Ma and correlates with similar along strike subduction zone magmatism in northwest India, Seychelles and Madagascar. During the final assembly of Gondwana in the early Paleozoic suturing of India-South China with the Western Australia-Mawson blocks along the Kuunga Orogen resulted in the accretion of the Sanya Block of Hainan Island with the rest of Cathaysia. The accretion of Laurussia to Gondwana in the mid-Paleozoic to form Pangea corresponds with the initiation of lithospheric extension along the northern margin of Gondwana and the separation of a number of continental blocks, including South China, which then drifted northward across the Paleo-Tethys to collide with the Asian segment of Pangea in the Permo-Triassic.
This paper reports some new results from U–Pb geochronological, Hf isotopic and REE geochemical studies of detrital zircons in the Ordovician sandstones from South Jiangxi within Cathaysia. 426 ...groups of U–Pb age determinations define five major age populations: 2560–2380
Ma (a peak of 2460
Ma), 1930–1520
Ma (a peak of 1700
Ma), 1300–900
Ma (a major peak at 970
Ma and two subordinate peaks at 1250
Ma and 1130
Ma), 850–730
Ma (a prominent peak of 780
Ma) and 670–530
Ma (a major peak at 540
Ma and a subordinate peak at 650
Ma). We also report zircon U–Pb concordia age of 3.96
Ga, which is the oldest age so far obtained from Cathaysia. The age peak at 2460
Ma correlates with similar ages reported for Neoarchean global continental growth. The 1930–1520
Ma population broadly overlaps with the time of amalgamation and disruption of the Columbia supercontinent. The major age peak at 970
Ma and two secondary peaks at 1250
Ma and 1130
Ma reflect multiple tectonothermal events associated with the assembly of Rodinia. Similar ages are widely reported from the South China Craton (SCC). Our study reveals that the 850–730
Ma population is consistent with the breakup period of Rodinia, suggesting that the SCC within Rodinia began to break up since 850
Ma. Geologically, the evidence for this breakup event is widespread and presented by Neoproterozoic granites, bimodal igneous rocks, basic dyke swarms and formation of continental rift type basins. Our study also reveals a 670–530
Ma population that correlates well with the assembly of Gondwana during end Neoproterozoic. However, direct geological evidence for this event has not yet been found within the studied area. Furthermore, the Hf isotopic model age data suggest two major stages of crustal evolution within Cathaysia. The first is the event dated at 1.6–2.8
Ga and the second one at 3.5–3.9
Ga. The zircons show a large range of εHf(t) values from +
8.64 to −
30.54, suggesting that they have different origins with a similar age of crystallization. The fact that most detrital zircons show negative εHf(t) values suggests the ancient provenances of Cathaysia were dominated by reworked crustal materials.
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► U-Pb age, Hf isotopes and REE geochemistry of detrital zircons in Orodovician sandstones from Cathaysia are presented. ► The data provide insights into continental growth of South China during Neoarchean. ► The data trace the link with the Proterozoic supercontinents of Columbia (1930–1520 Ma), Rodinia (1300–730 Ma) and Gondwana (670–530 Ma). ► The Gondwana signature is reported for the first time. ► The negative εHf(t) values of most zircons suggest a reworked crustal materials dominated provenance for Cathaysia.
The South China Block is situated in the Eastern Asian margin. Since the Neoproterozoic, its tectonic evolution was constrained by successive consumption-closure processes of the Paleo-South China, ...Proto-Tethys, Paleo-Tethys, and Paleo-Pacific oceans. Studies suggest that this block was initially formed by the Neoproterozoic assembly of the Yangtze and Cathaysia blocks following the subduction-accretion of the Paleo-South China Ocean. Then after, it experienced three tectonic-magmatic events in the Phanerozoic. Among these events, the Late Mesozoic tectonism-magmatism was linked with the consumption of the Paleo-Pacific Ocean, while the Silurian and Early to Middle Triassic events took place in intracontinental settings that were related to far-field effects of the closure of the remote Proto-Tethys and Paleo-Tethys oceans, respectively. The subduction-accretion of the Paleo-South China Ocean, and collision at 980–820 Ma between the Yangtze and Cathaysia blocks formed the Jiangnan Orogenic Belt and the Proto-South China Continent, followed by a rifting tectonics and bimodal volcanism at 810–760 Ma. From 760 Ma to 460 Ma, the South China Block was situated under shore, shallow sea to slope depositional environments. During Late Ordovician to Early Devonian (460–400 Ma), an intracontinental orogeny occurred mainly in the Cathaysia Block as a response to the closure of the Proto-Tethys Ocean. Shortly afterwards, this block underwent a stable carbonate deposition during Early Devonian- Middle Triassic (400–230 Ma) and was thus under a shore or shallow sea environment. In the Middle-Late Triassic (240–220 Ma), the South China Block was affected by the closure of the Paleo-Tethys Ocean, intracontinental deformation and S-type granitic magmatism. During the Cretaceous, a multi-stage basin-and-range framework occurred in the western shore of the Paleo-Pacific Plate.
•The 848 Ma anorthosite was found in the E-Jiangnan ophiolite and the 860–830 Ma intermediate-felsic rocks display active margin signature.•The 870–860 Ma ophiolite shows N- and E-MORB features and ...the 817 Ma K-granite marks the collision event.•Identification of western suture zone and the timing of final assembly of South China proposed as 830–800 Ma.
The Jiangnan orogenic belt in South China, formed by the collision of the Yangtze and Cathaysia sub-blocks, represents a key to reconstruct the assembly of the Rodinia supercontinent. Here we investigated the Fuchuan ophiolite mélange and Shexian magmatic units in the eastern Jiangnan belt, and report the first findings of anorthosite and leucogranite that are dated at 848 ± 4 and 840 ± 5 Ma, respectively. The anorthosites yield positive εNd(t) values (2.3–4.2) and lower initial 87Sr/86Sr ratios (0.704616–0.704679), along with zircon εHf(t) of ∼9.2, suggesting a depleted mantle contribution with minor crustal assimilation. The mafic-ultramafic rocks and anorthosite within the Fuchuan ophiolite display N-MORB & E-MORB signatures, likely generated in back-arc marginal sea spreading center and metasomatized by subduction-related fluids. The intermediate-felsic igneous suites from Shexian area in the eastern margin of the Zhanggong Terrane were formed at 850–830 Ma and display continental-arc-related geochemical features. Zircons within these rock suites mostly show εHf(t) values of 3–12, whereas inherited grains yielded negative εHf(t) values with model ages of 2.7–1.9 Ga, implying an active continental marginal environment. Overall relations and data indicate that the disrupted Fuchuan mafic-ultramafic rocks, anorthosite and leucogranite constitute the remnants of an 860–830 Ma ophiolite, whereas the northwestward subduction beneath the Zhanggong terrane occurred at ca. 870–860 Ma to ca. 830 Ma. A ca. 817 Ma muscovite-bearing K-granitic pluton dated at 817 ± 5 Ma emplaced in a post-collisional setting constrains the upper age limit of continental assembly along the Shaoxing- Jiangshan- Pingxiang- Qidong-Quanzhou- Longsheng-Yongfu fault zone. The timing of the final assembly of South China occurred at 830–800 Ma as referred from a collisional-type granitic magmatism ca. 830–815 Ma and an external dynamic process of uplifting-erosion-transpotation-deposition presented by the regional-scale unconformity with ages 820–795 Ma. Age and nature of the Jiangnan orogenic belt, along with sedimentary records and paleomagnetic constraints, indicate that the South China Block was possibly located along the northern Rodinia margin, adjacent to the Tarim and northwestern Australia blocks.
•N-MORB type basalts are identified from the west Jiangnan orogenic belt.•Ca. 863Ma Mafic suites in the eastern and western segments of the belt show arc related signatures.•Amalgamation of Yangtze ...and Cathaysia Blocks in the eastern part after ca. 863Ma, followed by breakup at ca. 790Ma.
The early Neoproterozoic Jiangnan orogenic belt, located in the southeastern margin of the Yangtze Block, is considered to mark the suture zone between the Yangtze and Cathaysia Blocks. The eastern part of this belt consists of the Huaiyu and Jiuling terranes, separated by the NE Jiangxi fault zone which represents the back-arc marginal sea. The western part of the Jiangnan orogenic belt is characterized by the Jiangnan arc and back-arc sea. Neoproterozoic mafic–ultramafic rock suites are exposed along both the Jiangshan-Shaoxing-Pingxiang-Shuangpai and the NE Jiangxi suture zones, whereas I-, S- and A-type granites occur widely in the Jiangnan region. Here, we present new LA–ICP–MS zircon U–Pb data, Hf isotopes and whole rock geochemistry for the mafic rocks and granite from the Jiangnan orogenic belt. The N-MORB (normal mid-ocean ridge basalts) type basalts from the Nanqiao of Liuyang area in the west Jiangnan orogenic belt show low K2O contents (0.74–0.16wt.%), belonging to tholeiitic series, and display LREE (light rare earth element) depleted REE (rare earth element) patterns, with positive Pb, Sr anomaly and minor negative Ti anomalies. The other mafic suites in the Daolinshan, Yiyang and Liuyang areas exposed in the eastern and western segments of the Jiangnan orogenic belt show distinctive geochemical signatures of volcanic arc, with zircon U–Pb ages of 863±6 Ma. Most of these rocks show negative Nb, Ta, Zr, Hf and Sr anomalies and have LREE enriched REE patterns, with minor negative Eu anomaly. These features coincide with those of the arc and fore-arc rock assemblages in the eastern Huaiyu Terrane and adjacent areas. Anorogenic granites of 790±5Ma are also found in the Daolinshang area. Our Hf isotopic data further reveal that the zircons from both the dolerite and A-type granite in the Daolinshan area possess positive ɛHf(t) values, yielding latest Mesoproterozoic to early Neoproterozoic model ages. Combined with previous studies, our data confirm the existence of an arc-trench system in the Jiangnan orogenic belt at ca. 863Ma. Therefore, we infer that the amalgamation of the Yangtze and Cathaysia Blocks in the eastern part occurred at some time after ca. 863 Ma. This was followed by breakup at ca. 790Ma which was triggered by mantle upwelling, as evidenced by the Daolinshan A-type granite with positive ɛHf(t) values
•854Ma mafic–ultramafic rocks from west Jiangnan Orogen were emplaced in arc setting.•830–820Ma S-type Yuanbaoshan granite pluton was emplaced in syn-collisional setting.•The assembly age of the ...Yangtze and Cathaysia Blocks is constrained at ca. 850–830Ma.
The Jiangnan Orogen is considered as the trace of the collisional suture between the Yangtze and Cathaysia Blocks in South China. Here we investigate the mafic–ultramafic suites and granitoids exposed in the Yuanbaoshan area along the western segment of the Jiangnan Orogen. We present new LA-ICP-MS zircon U–Pb data, Hf isotopes and whole rock geochemistry from a suite of granite, gabbro diorite and mafic–ultramafic rocks from this area. Zircons in the mafic rocks yield a U–Pb age of 854.7±5.3Ma, whereas those from the granites show ages of 822.6±5.2, 830.7±5.0, 823.8±5.3 and 833.0±5.9Ma. The Neoproterozoic mafic–ultramafic rocks display dominantly tholeiitic features and are characterized by negative Ba, Nb, Ta, Zr, Hf and Sr anomalies and LREE enriched patterns, with a minor negative Eu anomaly. The gabbro diorite also exhibits similar geochemical characters. The mafic suite plots in the field of volcanic arc basalt in tectonic discrimination diagrams and displays distinctive geochemical signatures of an arc setting. The zircons from these rocks show ɛHf(t) values in the range of 3.9–13.8. The granitoids in northern Guangxi are typical S-type granites with high ACNK values (1.15–1.40), and are classified as collision-related granites in tectonic discrimination diagrams. The zircons from these rocks show negative ɛHf(t) values of −18.99 to −0.84. We correlate the granitoids with the continent–continent collisional orogeny between the Yangtze and Cathaysia Blocks. Our new results suggest a ∼854Ma volcanic arc and an 840–820Ma collisional setting in the western segment of the Jiangnan Orogen, which is different from previous proposals of plume and bimodal magmatic settings and place the timing of assembly of the Yangtze and Cathaysia Blocks at some time ca. 850–800Ma.
Initiation of Mariana-type oceanic subduction zones requires rheologically strong oceanic lithosphere, which developed through secular cooling of Earth's mantle. Here, we report a 518 Ma Mariana-type ...subduction initiation ophiolite from northern Tibet, which, along with compilation of similar ophiolites through Earth history, argues for the establishment of the modern plate tectonic regime by the early Cambrian. The ophiolite was formed during the subduction initiation of the Proto-Tethys Ocean that coincided with slab roll-back along the southern and western Gondwana margins at ca. 530-520 Ma. This global tectonic re-organization and the establishment of modern plate tectonic regime was likely controlled by secular cooling of the Earth, and facilitated by enhanced lubrication of subduction zones by sediments derived from widespread surface erosion of the extensive mountain ranges formed during Gondwana assembly. This time also corresponds to extreme events recorded in climate and surface proxies that herald formation of the contemporary Earth.
•Ca. 871–864Ma arc-type olistostromal andesite within Dengshan Group are identified.•The entering of olistostromes into covering sequence occurred at ca. 810–800Ma.•A ca. 860–810Ma amalgamation of ...Yangtze and Cathaysia blocks is proposed.
The Jiangnan orogenic belt in South China defines a subduction-collisional zone between the Yangtze and the Cathaysia blocks. The eastern part of this belt comprises the oceanic Huaiyu terrane, the northeast Jiangxi suture zone and the continental Jiuling terrane. We report zircon U–Pb and Hf isotope data and whole rock geochemistry on the arc magmatic rocks of andesite and basalt occurring as olistostromal blocks, as well as conglomerate in the Dengshan Group above the unconformity between cover sequence and the volcanic arc units. The andesites yield weighted mean ages of 864Ma, 868 and 871Ma, whereas the detrital zircons from the conglomerate yield a major age population of 863–810Ma (peak of 833Ma), with two minor ones of 1120–940Ma (peak at 960Ma) and 1780–1560Ma (1670Ma). A post-ca. 810Ma depositional age is thus suggested for the Dengshan Group. The influx of olistostromal deposits into the Dengshan Group must post-date the youngest detrital zircon age of 810Ma and is possibly related to the widespread Nanhua rifting associated with the breakup of Rodinia. Furthermore, the age distribution of detrital zircons from the phyllite associated with the arc units compared to its depositional age also suggest a convergent setting, and those from the conglomerate are plotted into a similar field. The andesite and basaltic trachyandesite have LREE enriched patterns, with minor negative Eu anomaly, and negative Nb, Ta, Cs and Ti anomalies. However, the basalt displays only minor LREE enrichment, with no Eu anomaly, and almost flat spidergram trace element patterns, except for a minor positive Sr, Ba and Ti anomaly and negative Rb anomaly. The andesite and basaltic trachyandesite are all plotted in the field of volcanic arc, suggesting an arc setting. The basalt is plotted between EMROB and volcanic arc domains, suggesting magma generation from metasomatised sub-arc sources with subducted oceanic components. The Hf isotopic data on zircons from the andesite yield positive ɛHf(t) values of 2.79–15.51 and late Mesoproterozoic model ages, suggesting that the Neoproterozoic arc sources include reworking of subducted late Mesoproterozoic materials. Our results show that the amalgamation of the Yangtze and Cathaysia blocks in the eastern part occurred at some time between ca. 864Ma and ca. 810Ma.
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