Geological reconstructions of the East Asian blocks: From the breakup of Rodinia to the assembly of Pangea

Closure of the Proto-Tethys Ocean and Early Paleozoic amalgamation of microcontinental blocks in East Asia

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Insights into the tectonic evolution of the North China Craton through comparative tectonic analysis: A record of outward growth of Precambrian continents

Early Paleozoic tectonic evolution of the North Qinling Orogenic Belt in Central China: Insights on continental deep subduction and multiphase exhumation

The North China Craton (NCC) has had a long geological history back to ca. 3.8 Ga ago. In the Anshan area, northeastern part of the craton, three distinct complexes with ages of 3.8–3.1 Ga (Baijiafen, Dongshan, and Shengousi) have been identified, along with widespread 3.1–2.5 Ga rocks of different origins and ages. In eastern Hebei Province, abundant 3.88–3.4 Ga detrital zircons were obtained from metasedimentary rocks of the Caozhuang Complex, and the oldest rock identified is a 3.4 Ga gneissic quartz diorite. The oldest zircons that may originally have been derived from the NCC are 4.1–3.9 Ga grains in Paleozoic volcano-sedimentary rocks in the northern Qinling Orogenic Belt bordering the NCC in the south. 3.0–2.8 Ga rocks occur in Anshan, eastern Hebei, eastern Shandong, and Lushan. ca. 2.7 Ga rocks of igneous origin are exposed in eight areas of the NCC, but ~2.7 Ga supracrustal rocks have so far only been identified in western Shandong. ca. 2.5 Ga intrusive and supracrustal rocks and associated regional metamorphism occur in almost all Archean areas of the NCC. Banded iron formations contain the most important ore deposit of the Archean in the NCC and mainly formed during the late Neoarchean. Ancient crustal records obtained from deep crust beneath the NCC are similar to those in the exposed areas, with the oldest ca. 3.6 Ga rock enclaves occurring in Xinyang near the southern margin of the NCC. This synthesis is based on the compilation of a large database of zircon ages as well as whole-rock Nd isotopic and Hf-in-zircon isotopic data in order to understand the formation and evolution of the early Precambrian basement of the NCC. Considering the craton as an entity, there is a continuous age record from 3.8 to 1.8 Ga, and two tectono-thermal events are most significant in the late Neoarchean to the earliest Paleoproterozoic and late Paleoproterozoic history, with age peaks at ~2.52 and ~1.85 Ga, respectively. Whole-rock Nd and Hf-in-zircon isotopic data show similar features, documenting the addition of juvenile material to the continental crust at 3.8–3.55, 3.45, 3.35–3.3, 2.9, and 2.85–2.5 Ga with the late Mesoarchean to early Neoarchean being the most important period. Crustal recycling began as early as 3.8 Ga and continued until 3.25 Ga and appears to have played a more important role than juvenile additions between 3.25 and 2.90 Ga. After outlining the general geological history of the NNC basement, we discuss several issues relating to Archean crust formation and evolution and arrive at the following major conclusions: (1) Similar to several other cratons, the late Mesoarchean to early Neoarchean was the most important period for rapid production of continental crust, and the most intensive and widespread tectono-thermal event occurred at the end of the Neoarchean. (2) In our new tectonic model, we define and outline three ancient terranes containing abundant 3.8–2.6 Ga rocks, namely the Eastern Ancient Terrane, Southern Ancient Terrane, and Central Ancient Terrane. (3) Vertical magmatic growth is seen as the main mechanism of crust formation prior to the Mesoarchean. We favor a multi-island arc model related to subduction/collision and amalgamation of different ancient terranes in the late Neoarchean. (4) The NCC may already have been a large crustal unit as a result of cratonic stabilization at the end of the late Neoarchean, probably due to magmatic underplating.

Formation and Evolution of Archean Continental Crust of the North China Craton

Early Paleoproterozoic (2.45-2.20Ga) magmatic activity during the period of global magmatic shutdown: Implications for the crustal evolution of the southern North China Craton

The Qinling Complex of central China is thought to be the oldest rock unit and the inner core of the North Qinling Orogenic Belt (NQOB). Therefore, the Qinling Complex is the key to understanding the pre-Paleozoic evolution of the NQOB. The complex, which consists of metagraywackes and marbles, underwent regional amphibolite-facies metamorphism. In this study, we constrained the formation age of the Qinling Complex to the period between the late Mesoproterozoic and the early Neoproterozoic (ca. 1062–962 Ma), rather than the Paleoproterozoic as previously thought. The LA-ICP-MS data show two major metamorphic ages (ca. 499 and ca. 420–400 Ma) for the Qinling Complex. The former age is consistent with the peak metamorphic age of the high- and ultra-high pressure (HP-UHP) rocks in the Qinling Complex, indicating that both the HP-UHP rocks and their country rocks experienced intensive regional metamorphism during the Ordovician. The latter age may constrain the time of partial melting in the NQOB between the late Silurian and early Devonian. The Qinling Complex is mostly affiliated with subduction–accretion processes along an active continental margin, and should contain detritus deposited in a forearc basin. The available data indicate that the NQOB was an independent micro-continent at least prior to the Neoproterozoic, and included a portion of the Grenville orogenic belt during the period of 1.2–0.8 Ga. The NQOB has experienced a unique geological history, which is obviously different from that of the North China Craton (NCC) and the Yangtze Craton during the Precambrian. The Neoproterozoic granitoids that intruded the Qinling Complex can be interpreted as the products of assembly of the supercontinent Rodinia. The NQOB was separated from Rodinia at ca. 830–740 Ma. Subsequently, the NQOB moved closer to the northern margin of the NCC, and the initial accretion or collision with the NCC occurred from the late Cambrian to the early Ordovician.

Geochronological, geochemical, and Nd-Hf isotopic studies of the Qinling Complex, central China: Implications for the evolutionary history of the North Qinling Orogenic Belt

Archean-Paleoproterozoic crustal evolution of the Ordos Block in the North China Craton: Constraints from zircon U–Pb geochronology and Hf isotopes for gneissic granitoids of the basement

Late Neoarchean to early Paleoproterozoic tectonic evolution of the southern North China Craton: Evidence from geochemistry, zircon geochronology and Hf isotopes of felsic gneisses from the Taihua complex

The Archean-Paleoproterozoic metamorphic basement is well exposed in the southern North China Craton (NCC), and can be divided into three distinct tectonic complexes, naming, the Sushui, Dengfeng and Taihua complexes. Their equivalents probably extend into the Huoqiu and Bengbu areas of Anhui Province in the southeastern margin of the NCC, and the Longshan area of Gansu Province in the southwestern margin. In the last decade, a large number of the Mesoarchean–Neoarchean (ca. 2.85–2.50 Ga) rocks have been widely recognized in those complexes, which provides important insights into the formation and evolution of NCC during this period. Based on the available isotopic data, the Archean continental crust of the southern NCC can be divided into the 2.85–2.70 Ga and ca. 2.50 Ga rock associations. Most of zircons in the 2.85–2.70 Ga rocks that consist predominantly of TTG gneisses have variable but positive e Hf(t) values, and their magmatic zircon domains that are characterized by oscillatory zoning in CL images present mantle-like O isotopes, reflecting a somewhat geochemically heterogeneous but depleted mantle Hf isotope reservoir dominates the source of these rocks. The whole-rock Nd isotopic data show similar geochemical characteristics, confirming juvenile sources for their provenance. Although majority of Chinese Precambrian geologists suggested that the ca. 2.50 Ga tectonothermal events were mainly involved in crustal reworking or partial melting of the early Neoarchean mafic crust formed at 2.85–2.70 Ga, we emphasize that ca. 2.50 Ga is another major period of continental crust growth in the southern NCC as well as the whole NCC based on the following lines of evidence: (1) a variable proportion of metabasaltic rocks with ca. 2.50 Ga zircon U–Pb ages exposed in both the high-grade gneissic complexes and the low-grade granite-greenstone terrenes. (2) the metabasaltic rocks present mixed MORB- and/or arc-like geochemical affinities, suggesting that they were derived from mantle source with minor continental crust contamination. (3) most of the ca. 2.50 Ga magmatic zircons from TTG gneisses, amphibolites and related rocks have positive e Hf(t) values that are similar to those of the contemporaneous depleted mantle, and their Hf model ages of 2.85–2.49 Ga are close to corresponding U–Pb ages, suggesting that these rocks originated from the juvenile crust at ca. 2.50 Ga. (4) the whole-rock Nd isotopic data of the ca. 2.50 Ga rocks show similar geochemical characteristics, confirming juvenile sources for their provenance. In summary, we suggeste that the southern NCC underwent two marked episodes of continental crust growth at 2.85–2.70 Ga and ca. 2.50 Ga during the Archean, and all the complexes in the southern NCC were welded together to form a coherent ancient terrane at the end of the Neoarchean, we named it the “Southern Archean Block (SAB)”. The SAB show an east–west trending belt from Gansu across Shaanxi and Henan into Anhui Province, stretching over 1000 km long, it may has experienced a long geological history which can be traced back to the Hadean. The ca. 2.50 Ga K-rich granitoid rocks were recognized from the southern NCC, which are commonly considered as the proxy of the final stabilization of the block lithosphere.

Yong Sun

Papers

Early Paleoproterozoic (2.45-2.20Ga) magmatic activity during the period of global magmatic shutdown: Implications for the crustal evolution of the southern North China Craton

Geochronological, geochemical, and Nd-Hf isotopic studies of the Qinling Complex, central China: Implications for the evolutionary history of the North Qinling Orogenic Belt

Archean-Paleoproterozoic crustal evolution of the Ordos Block in the North China Craton: Constraints from zircon U–Pb geochronology and Hf isotopes for gneissic granitoids of the basement

Late Neoarchean to early Paleoproterozoic tectonic evolution of the southern North China Craton: Evidence from geochemistry, zircon geochronology and Hf isotopes of felsic gneisses from the Taihua complex

Archean Continental Crust in the Southern North China Craton