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• The Lechangxia and Bacun groups in the Cathaysia Block was deposited during Ediacaran and early Cambrian. • These successions formed in passive setting, except for the mid Bacun Group in collisional setting. • A mid Cambrian uplift led to a provenance change from exotic to intrinsic sources in the Cathaysia Block. • The Cathaysia Block was linked to east Gondwana at lease since ca. 630 Ma. Paleogeographic reconstruction of the Cathaysia Block of South China and its link with orogeny associated with Rodinia and Gondwana remain enigmatic, leading to controversial models proposed for supercontinental configuration. This study presents detailed provenance analysis of late Neoproterozoic to early Paleozoic sedimentary successions from the Cathaysia Block, to trace the sedimentary provenance, that was essentially linked to previously adjacent continents/blocks. Zircon U-Pb dating combined with published paleontological evidence suggests an Ediacaran depositional age range (633–542 Ma) for the Lechangxia Group, while deposition of the Bacun Group most likely commenced during early Cambrian. The older strata were sourced mainly from recycling of quartz rich sedimentary rocks while the younger one received sediments dominantly from felsic igneous rocks. High SiO 2 contents (54.6–79.3 wt%) and K 2 O/Na 2 O ratios (0.69–35.7), detrital zircon age distribution and abundant monocrystalline quartz indicate a passive setting for Ediacaran and early Cambrian successions. In great contrast, the middle Cambrian strata was likely deposited in collisional setting, considering relatively lower SiO 2 contents (67.9–74.5 wt%) and K 2 O/Na 2 O ratios (0.97–1.63) plus absence of old zircons. This tectonic transition is consistent with the change from quartz arenite to arkose that could be related to a disconformity between early and middle Cambrian strata. Dominant late Mesoproterozoic detritus (1250–1050 Ma) in the Lechangxia Group was possibly sourced from older Grenville orogens (1300–1050 Ma) in western Australia and East Antarctica because rocks of these ages are rare in the Cathaysia Block. Similarly, abundant early Neoproterozoic clastic (1000–950 Ma) in the late Ediacaran and early Cambrian successions imply an increasing input from younger Grenville orogens (990–950 Ma) in East Antarctica and eastern India. Thus the Cathaysia Block was a part of the East Gondwana assembly and was linked to eastern India, East Antarctica and western Australia during Ediacaran and Cambrian. The source change was coeval with the Pinjarra Orogeny (550–520 Ma) and the early stage of the Kuunga Orogeny (570–550 Ma). In middle Cambrian strata, the middle Neoproterozoic sediments (850–700 Ma) were mainly derived from intrinsic sources, likely to be the Wuyishan terrane. This provenance variation can be linked to the middle Cambrian uplift of the Cathaysia Block in synchronous with the later phase of the Kuunga Orogeny (530–480 Ma). [ABSTRACT FROM AUTHOR]

The Neoproterozoic Jiangnan Orogenic Belt in south China was formed by the amalgamation of the Yangtze and Cathaysia blocks, however, the timing of its formation is still debated. In this study, we present whole rock geochemistry, U-Pb zircon ages, Lu-Hf and Nd-isotope systematics on the Neoproterozoic Yexijiang and Baomuping granites occurring in the western segment of the Jiangnan Orogenic Belt. These granites mark the initiation of post-collision extension environment. Zircon U-Pb age data identify 807–805 Ma emplacement age for these granites. They have low and variable ΣREE concentrations (47–115 ppm) and show moderate to highly fractionated REE patterns ([La/Sm] N = 2.83–3.78) with low [Gd/Yb] N (1.34–2.31) and negative Eu anomalies (Eu* = 0.34–0.57). Geochemical features and presence of peraluminous minerals classify them as S-type granites and P-T parameters indicate low to moderate temperature (730–791 °C) and pressure (middle crustal level) conditions. These granites show consistent negative whole rock ɛNd(t) (−5.7 to −6.6) and magmatic zircon ɛHf(t) values from −0.3 to −3.8 while inherited zircon grains show variable ɛHf(t) values (+2.1 to −13.0) and two-stage Hf model ages (1.80 to 2.88 Ga). In particular, one Neoproterozoic (899 Ma) inherited zircon grain displays depleted Hf [ɛHf(t) = +5.4 and T DM2 = 1.34 Ga] isotopic characteristic. These lines of evidence indicate a sedimentary source for Yexijiang and Baomuping granites, possibly the Archean to Neoproterozoic crustal rocks, and emplacement in a post-collision tectonic environment triggered by mafic magma underplating during the amalgamation of the Yangtze and Cathaysia blocks. We infer that convergence in the Jiangnan Orogenic Belt occurred during 830–800 Ma therefore, unrelated to the global Grenvillian Orogeny. • 805 Ma granites from the Jiangnan Orogenic Belt show S-type affinity and were formed in a post-collision setting. • Neither fractional crystallization nor magma mixing played an significant role in magma evolution. • The Jiangnan Orogeny was formed at 830-800 Ma, significantly younger than the Grenvillian Orogeny. [ABSTRACT FROM AUTHOR]

The geological evolution of the Central African Fold Belt (CAFB) remains debated. The granitoids, orthogneisses and granitic veins from the Goa-Mandja area (Adamawa-Yade domain) are considered to constrain this belt. These rocks are consistent with late-D 2 regional emplacement and synchronous with the magmatism at ~600 Ma within the CAFB in Cameroon and its extension into northeastern Brazil, as the zircon U Pb dating points to 603–598 Ma crystallization ages. Analytical data reveal slightly elevated δ18O zrn (6.45–7.17‰) and δ18O WR (8.20–8.61‰), moderate to high SiO 2 (59.70–77.23 wt%), low MgO (0.07–2.77 wt%), Cr (0.29–55.12 ppm), Ni (0.45–33.6 ppm), V (1.52–116.62 ppm) and Mg# (0.02–0.36) contents, indicating crustal origin. The low to medium 87Sr/86Sr i (0.703328–0.722670) and positive to negative ε Nd(t) (+5.7 to −9.9), coupled with the diversity of Nd model ages (T DM2) support the heterogeneity of crustal protoliths. The high positive ε Nd(t) (+5.7) of the granitic vein indicates derivation from juvenile Neoproterozoic (Nd-T DM2 at 854 Ma) crustal protolith. T DM2(Nd) and T DM2(Hf) ages of 1188–2120 Ma and 2173–2480 Ma also suggest the involvement of Mesoproterozoic to Paleoproterozoic crustal protoliths. Samples show metaluminous to weakly peraluminous, high-K calc-alkaline to shoshonitic and I-type granitoid features and are similar with crustal rocks in regard to LILE (Rb, K) and LREE enrichments and HFSE (Nb, Ta, Ti) depletions. These combined features indicate slab subduction related setting for the magma generation. Slab subduction may have generated the heat necessary to provoke partial melting at the lower crustal level. Considering their position close to the Tchollire-Banyo Fault corridor, at the transition between the Adamawa-Yade and northern domains, the subduction derived features shown by the Goa-Mandja I-type granitoids could be related to the subduction of an old plate boundary during amalgamation of Gondwana. Therefore, the Goa-Mandja area records dominant magmatic accretion along the northern margin of the Congo craton (active margin) associated with a possible northwestern subduction. • The Goa-Mandja granitoids formed at 603–598 Ma. • Variable types of granitoids are identified in the Goa-Mandja area. • They were originated from heterogeneous crustal protoliths. • They are related to the subduction of an old plate boundary during Gondwana assembly. [ABSTRACT FROM AUTHOR]

• The Linte massif reveals a protracted magmatism which lasted at least 60 Ma. • Rocks show geochemical affinities of I-type, shoshonitic and metaluminous granitoids. • The 660 and 630 Ma rocks originate from source involving mantle material which could have been mingled or mixed with crustal component while the 600 Ma rocks come from crustal material. • They were formed during the syn- collisional phase of the Pan-African orogeny. The Central African Fold Belt (CAFB) holds a key position in understanding the process and implications of the Pan-African orogeny in central Africa. However, it has not been fully understood as geological information on some vital domains is not yet available. The Linte massif in the Adamawa-Yade, one of the unrepresented terranes, was investigated and its whole rock geochemical, zircon U-Pb geochronology and Hf-O isotope characteristics and whole rock Sr-Nd data are presented and discussed here. The Linte massif is largely constituted of syenite and subordinate monzonite. The zircon U - Pb dating reveals three major ages at 660, 630 and 600 Ma, indicating a protracted magmatism which lasted at least 60 Ma, during the Neoproterozoic. The rocks are shoshonites, I-type and metaluminous. They have high LILEs (Cs, Rb, Ba and Sr), HFSEs (Th and U) and LREE contents. Their Nb/U, Ta/U, Ce/Pb, Th/La and Th/U ratios, δ18O zrn (5.3–7.6‰) and zircon εHf(t) (−14.7 to +3.2), point toward predominantly crustal with or without a mantle component in the sources. The negative εNd(t) values (−8.1 to −10.0), Paleoproterozoic Nd-T DM model ages (ca. 1700–1900 Ma), Hf-T DM2 ages of ca. 1300–2400 Ma of zircon grains in Neoproterozoic rocks underline their derivation from Mesoproterozoic to Paleoproterozoic basement rocks. The lithospheric mantle-generated heat facilitated partial melting in the sources region, as inferred from the shoshonitic affinity and the subduction-related geochemical features (Nb, Ta and Ti depletion). A mainly crustal source with a minor mantle component is inferred for the 660 Ma magmatism and for the 630 Ma rocks emplaced during crustal thickening. On the other hand, the 600 Ma (youngest) magmatic rocks were derived from a crustal source. We infer a subduction-collision setting for the Linte massif during the 660–600 Ma interval. The 630–600 Ma interval of the culmination of collision is consistent with the timing of the main convergence of the Brasiliano Orogeny recorded in South America (∼630–600 Ma), suggesting continuation of tectonic features into the western Gondwana. [ABSTRACT FROM AUTHOR]

• Protolith of Nkondjock orthogneisses crystallized at 607 ± 4, 624.4 ± 3.5 and 621 ± 9.1 Ma. • The Nkondjock orthogneisses show geochemical affinity of S- and I-type granitoids. • They were derived from thickened low crust and mature continental crust. • They were formed during the collision between the Congo and West African craton. The Nkondjock area located in Western Cameroon is part of the Neoproterozoic Central African orogenic belt, at the northern border of the Congo craton. Rocks of the Nkondjock area are: two-mica orthogneisses, two-pyroxene orthogneisses and mylonitic orthogneisses. The protolith of two-mica, two-pyroxene and mylonitic orthogneisses crystallized at 607 ± 4, 624.4 ± 3.5 and 621 ± 9.1 Ma, respectively, and are thus consistent with the Central African Orogenic belt. Inherited zircons (2043 ± 27 Ma) of mylonitic orthogneisses are interpreted as an inherited age of the metacratonization of the northern border of the Congo craton. S-type affinity of two-mica orthogneisses together with two-pyroxene orthogneisses (Mabombé) display geochemical affinities typical of adakite, including high La/Yb N (29.7–55.6) and low Y (3.43–6.69 ppm) with low Mg# (30.8–55), εNd(t) (−8.6 to −6.5), high 87Sr/86Sri (0.70684–0.71063) and positive εHf(t) (+3 to +4.9), similar to those adakites formed by partial melting of thickened lower crust with some mantle input. Two-pyroxene orthogneisses (Ndogboni) and mylonitic orthogneisses display I-type granitoids affinity with A/CNK (0.93–1.06) and are depleted in Nb, Ta, Sr, P, Ti and enriched in Rb, Th, and Pb. They also have low εNd(t) (−10.3 to −11), high 87Sr/86Sr i (0.71017–0.71063) and negative εHf(t) (−19.1 to −1) similar to melts derived from mature continental crust. Sr-Nd-Hf isotopes confirm heterogeneous source for these orthogneisses with bimodal distribution on εHf(t) and εNd(t) values, suggesting mixing between juvenile mafic melt and a mature continental crust during the evolution of the Central African Orogenic belt. We suggest that the protolith of these orthogneisses (S- and I-type granitoids) were formed during syn -collisional setting between the Congo and the West African craton which followed a subduction through partial melting of a thickened lower continental crust due to a thermal anomaly induced by upwelling of asthenosphere through slab break-off. [ABSTRACT FROM AUTHOR]