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Seamount chains (oceanic plateaus, submarine ridges) are unique morphologic features on the seafloor, which resulted from the motion of the lithosphere over a convective plume. Seamount chains are being carried along by plate motions, which are eventually subducted beneath continental/oceanic plates or accreted in the accretionary complex, thus causing a series of effects in the convergent margin. In this paper, we briefly review the distribution and features of the typical modern seamount chains, including Hawaiian‐Emperor and Louisville seamount chains, Cocos, Ninetyeast and Caroline ridges, and Ogasawara Plateau, and mainly focus on the effects of seamount chains subduction and accretion. The geological effects mainly include the following: (1) deformation and tectonic erosion of the overriding plate; (2) flat‐slab subduction in the convergent margin; (3) growth of continental crust through time; (4) subduction initiation of plate tectonics; (5) generation of large earthquakes; (6) magmatism of the volcanic arc; and (7) formation of porphyry copper and gold deposits. The subduction of seamount chains resulted in similar effects in the Central Asian Orogenic Belt (CAOB) which is one of the largest and longest‐lived accretionary orogens on Earth. However, there are still many aspects that need further improvements, such as identification of the seamounts in the geological record, and geodynamic effects of subducted seamount chains. A detailed study on these sides of the seamount chains will enable us to further understand the tectonic evolution and metallogenesis of the CAOB, especially in accretionary orogenesis, continental crust growth, and subduction initiation dynamics. [ABSTRACT FROM AUTHOR]

The Yining Massif, sandwiched between the Junggar and Tarim plates, has received much attention because of its special position and complex tectonic evolution, as well as a significant breakthrough in geological prospecting. Moreover, a lot of studies have focused on two suites of volcanic rocks of the Early Carboniferous Dahalajunshan and Late Carboniferous Yishijilike formations in the Yining Massif. Recently, an increasing number of results have shown that two suites of volcanic rocks have obvious differences in lithochemistry and geochemistry and might have formed in an arc and intracontinental rift settings, respectively. Furthermore, the latest results of Sr–Nd isotopes indicate that the initial (87Sr/86Sr)i ratio is less than 0.7119 for all samples in the two formations. But the (87Sr/86Sr)i of andesites in the Dahalajunshan Formation is obviously higher than that of the Yishijilike Formation. However, those of dacites and rhyolites are just the opposite. The (143Nd/144Nd)i of all kinds of rocks from the Dahalajunshan Formation is less than 0.5126, and that of basalts in Yishijilike Formation is also less than 0.5126. However, the results of the andesites and rhyolites are higher than 0.5126. In short, the parameters of (87Sr/86Sr)i, (143Nd/144Nd)i, εNd(t), TDM (Ga), and εSr(t) are different obviously between the two suites, showing progressive change from basic to acid rocks in the two formations (gradual increase and decrease), but the changed direction is just the opposite. Consequently, it illustrates that there is a significant distinction in composition and petrogenesis between the Dahalajunshan and Yishijilike formations. The Dahalajunshan Formation volcanic rocks might be derived from an enriched mantle, whereas the volcanic rocks in the Yishijilike Formation are related to the evolution of continental crust. In other words, the differentiation of Sr–Nd isotopes provides a reference information for studying the petrogenesis and tectonic setting of the two suites of volcanic rocks. [ABSTRACT FROM AUTHOR]

The South Tianshan Orogenic Belt (STOB) is situated in the southwest margin of the Central Asian Orogenic Belt and is characterized by the distribution of ophiolitic mélanges and metamorphic rocks. In this study, we focus on 5 ophiolitic mélanges with ocean island basalt (OIB) and aim to discuss the tectonic evolution of the South Tianshan Ocean. The Kynda, Kainar, Uchkel, Heiyingshan, and Guluogou ophiolitic mélanges in STOB mainly consist of metamorphic peridotite, gabbros, basaltic lavas (pillows), abyssal radiolarian cherts, and limestones. The basaltic rocks mainly occur as tectonic blocks within the mélanges. These basaltic rocks are characterized by LREE enrichment and HREE depletion, very weak or no Eu anomalies, and no obvious Nb, Ta, and Ti negative anomalies, positive εNd(t) values, relatively high initial 87Sr/86Sr ratios, and wide 206Pb/204Pb ratios, showing the signature of OIB. The OIB‐type rocks from Kynda, Kainar, and Guluogou are likely to be derived from garnet lherzolite by relatively high degrees of melting (10% to 20%). But the basaltic rocks of Uchkel and Heiyingshan formed at significantly lower degrees of partial melting (1% to 5%) of spinel and/or garnet lherzolite. The OIB‐type rocks in these ophiolitic mélanges are considered as accreted seamount fragments and may represent mantle plume‐related magmatism within the South Tianshan Ocean. In combination with previous work, we suggest an updated model, which is bidirectional oceanic subduction with seamounts accretion and subduction system, is suitable for Palaeozoic tectonic evolution of the South Tianshan Ocean. [ABSTRACT FROM AUTHOR]

The tectonic evolution and configuration of the Carboniferous trench‐arc‐basin system (TABS) in the Yining Massif (Western Tianshan, NW China) have long been controversial. The question of the existence of an ancient ocean basin and its subduction polarity is crucial to address this issue. In this study, we suggest that the Early Carboniferous calc‐alkaline volcano‐sedimentary rocks were formed in a fore‐arc/back‐arc basin system, whereas the Late Carboniferous bimodal volcanic rocks and their associated sedimentary rocks were formed under a continental rift setting after the Junggar‐Tarim collision. We propose that the Southern Tianshan ocean basin may have closed in the Late Early Carboniferous, terminating the TABS at Yining. Spatial–temporal distribution of volcanic‐sedimentary rock assemblages suggests that the Early Carboniferous Southern Tianshan ancient ocean basin was similar to the TABS system of the present‐day Japanese island arc. [ABSTRACT FROM AUTHOR]

The Qinling Orogen is located between the North China and South China blocks, and considered to form by the multiple accretionary processes, being also characterized by development of voluminous magmatic intrusions as well as abundant mineral resources. Here we compile the geological, geochemical and geochronological data of the Early Mesozoic granitoids from the Qingling Orogen and attempt to constrain the Early Mesozoic tectonic evolution and mechanism of gold mineralization in this region. The Early Mesozoic granitoids are most widespread in the Qinling Orogen, especially in western part, and can be classified into S-, I-, I-A-types, with the I-type constituting the major variety. The isotopic ages of the three types granitoids are 200-222 Ma, 185-248 Ma, 210-227 Ma, respectively, indicating overlapping ages with a wide span of I-type granitoids. The S-, I-, I-A-type granitoids show obvious zonation characteristics, that is the S-type granitoids only occurred in southern South Qinling Belt, the I-type granitoids are most widespread in the western Qinling Orogen, and the I-A-type granitoids are mainly exposed in the North Qinling Belt. The S-type granitoids crystallized at relatively low temperature (800-850 °C) and deep-crustal level (ca. 8 kb) and derived mainly from partial melting of a clay-poor psammitic source. The I-type granitoids formed at high temperature (>925 °C) and pressures above the garnet-in phase boundary (>1.2 GPa) and derived from greywackes and partially igneous source. Moreover, the I-A-type granitoids probably derived from distinct sources with sufficient interaction, or common origin but underwent different degrees of crustal contamination, and generated at high temperatures (ca. 950 °C) and low pressures (1.0-0.2 GPa) conditions. These features indicate the Qinling Orogen experienced subduction, syn-collisional, and post-collisional during the Early Mesozoic, and also suggest the S-, I-, I-A-types granitoids underwent an episodic growth documenting the tectonic regime switchover at this stage. The gold deposits in the western Qinling Orogen can be classified as orogenic, Carlin-type, and Carlin-like gold deposits with the formation age of Late Triassic. The orogenic and Carlin-type gold deposits have no genetic relation to granitic magmatism, but the Carlin-like gold deposits is related to the synchronous magmatism. Combined with regional geology and metallogenic systems, we suggest that the multi-stage Qinling Orogenesis resulted in the formation of the Early Mesozoic S-, I-, I-A-type granitoids and different types of gold deposits with some characteristic differences. [ABSTRACT FROM AUTHOR]

We present an overview of the internal structure of the 10 ophiolitic mélanges in the Central China Orogen (CCO) with a focus on the geochemical character and tectonic evolution of the ophiolitic mélange-related ocean island basalt (OIB) and mafic rock assemblages. The ophiolitic mélanges in CCO are generally complicated and usually consist of metamorphic peridotites (serpentinite), cumulates, gabbros, basaltic lavas (pillows), and abyssal radiolarian cherts. The ages of ophiolitic mélanges range from Mesoproterozoic to Carboniferous. The OIB-type basalts and mafic rocks in CCO occur as tectonic blocks within the mélanges that are composed of limestones, radiolarian cherts, and turbidites, possessing formation characteristics of seamounts (oceanic islands/plateau). The mafic rocks in ophiolitic mélanges of CCO display uniform chondrite-normalized rare earth element (REE) patterns with light REE enrichment and heavy REE depletion, no obvious Eu anomalies or negative Nb, Ta, and Ti anomalies, and primitive mantle-normalized trace element patterns with significant large-ion lithophile element enrichment, similar to those of modern OIB and the Hawaiian alkaline basalts. The OIB-type basalts and mafic rocks are considered as accreted seamount fragments in an accretionary complex of CCO and may represent plume-related magmatism within the Proto-Tethys Ocean and Paleo-Tethys Ocean. Our study provides further insights into the processes of multiple subduction and long-lasting accretionary histories with seamounts in the CCO. [ABSTRACT FROM AUTHOR]

Accretionary wedge is the typical product of subduction-zone processes at shallow depths. Determining the location, composition and mechanism of accretionary wedge has important implications for understanding the tectonism of plate subduction. The Central Asian Orogenic Belt (CAOB) is one of the world's largest accretionary orogenic belts, and records the bulk evolution of Paleo-Asian Ocean from opening to closure, with multi-stages and multi-types of crust-mantle interaction in the Paleozoic. West Junggar (western part of Junggar Basin), located in the core area of CAOB, is characterized by a multiple intra-oceanic subduction system during the Paleozoic. In its eastern part crop out Devonian-Carboniferous marine sedimentary rocks, Darbut and Karamay ophiolitic mélanges, alkali oceanic island basalts, island arc volcanic rocks and thrusted nappe structure. Such lithotectonic associations indicate the occurrence of accretionary wedge at Karamay. In order to decipher its formation mechanism, this paper presents a synthesis of petrography, structural geology and geochemistry of volcanic rocks. In combination with oceanic subduction channel processes, it is suggested that the accretionary wedge is a composite mélange with multiple stages of formation. The application of oceanic subduction channel model to the Karamay accretionary wedge provides new insights into the accretion and orogenesis of CAOB. [ABSTRACT FROM AUTHOR]

Zircon U–Pb geochronological and geochemical analyses are reported for a suite of the early Carboniferous volcanic rocks from West Junggar (Northwest China), southern Central Asian Orogenic Belt (CAOB), with the aim to investigate the sources, petrogenesis, and tectonic implications. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb analysis from an andesite yielded concordant weighted mean206Pb/238U age of 345 ± 3 Ma, indicating the presence of early Carboniferous volcanic rocks in West Junggar. The early Carboniferous volcanic rocks consist of basalt, basaltic andesite, and andesite. Geochemically, all the samples bear the signature of ocean island basalt (OIB), and are characterized by alkaline affinity with minor variations in SiO2compositions (45.13–53.05 wt.%), high concentrations of Na2O + K2O (5.08–8.89 wt.%) and TiO2(1.71–3.35 wt.%), and LREE enrichment and HREE depletion ((La/Yb)N = 7.1–12.4), with weak Eu anomalies (Eu/Eu* = 0.9–1.1) and no obvious Nb, Ta, and Ti negative anomalies. These features suggest that the early Carboniferous volcanic rocks were derived from an OIB-related source that consists of oceanic lithosphere with ~1–3% degree partial melting of garnet lherzolite. From these observations, in combination with previous work, we conclude that the early Carboniferous alkaline volcanic rocks in Karamay region formed by upwelling of asthenospheric mantle through a slab window in a forearc setting during consumption of the West Junggar Ocean. Meanwhile, seamounts, which formed in the Late Devonian and were accreted and subducted in Karamay arc, also brought geological effects in the subduction zone. [ABSTRACT FROM AUTHOR]

The article discusses the research study conducted to examine the geodynamic setting and tectonic model of porphyry copper?gold deposits in West Junggar, northwest China in the Central Asia Orogenic Belt (CAOB). It mentions that the porphyry deposit is associated with a late carboniferous intrusive complex. It reveals that the ore-bearing porphyry system was derived from partial melting of multiple sources including oceanic crust and a subduction-modified mantle wedge in paleo-Junggar ocean.

Abstract: The West Junggar domain in NW China is a distinct tectonic unit of the Central Asian Orogenic Belt (CAOB). It is composed of Paleozoic ophiolitic mélanges, arcs and accretionary complexes. The Sartuohai ophiolitic mélange in the eastern West Junggar forms the northeastern part of the Darbut ophiolitic mélange, which contains serpentinized harzburgite, pyroxenite, dunite, cumulate, pillow lava, abyssal radiolarian chert and podiform chromite, overlain by the Early Carboniferous volcano-sedimentary rocks. In this paper we report new geochronological and geochemical data from basaltic and gabbroic blocks embedded within the Sartuohai ophiolitic mélange, to assess the possible presence of a Devonian mantle plume in the West Junggar, and evaluate the petrogenesis and implications for understanding of the Paleozoic continental accretion of CAOB. Zircon U–Pb analyses from the alkali basalt and gabbro by laser ablation inductively coupled plasma mass spectrometry yielded weighted mean ages of 375±2Ma and 368±11Ma. Geochemically, the Sartuohai ophiolitic mélange includes at least two distinct magmatic units: (1) a Late Devonian fragmented ophiolite, which were produced by ca. 2–10% spinel lherzolite partial melting in arc-related setting, and (2) contemporary alkali lavas, which were derived from 5% to 10% garnet+minor spinel lherzolite partial melting in an oceanic plateau or a seamount. Based on detailed zircon U–Pb dating and geochemical data for basalts and gabbros from the Sartuohai ophiolitic mélange, in combination with previous work, indicate a complex evolution by subduction–accretion processes from the Devonian to the Carboniferous. Furthermore, the alkali basalts from the Sartuohai ophiolitic mélange might be correlated to a Devonian mantle plume-related magmatism within the Junggar Ocean. If the plume model as proposed here is correct, it would suggest that mantle plume activity significantly contributed to the crustal growth in the CAOB. [Copyright &y& Elsevier]