The Sanjiang region in SE Tibet Plateau and NW Yunnan is known to have formed by amalgamation of Gondwana-derived continental blocks and arc terranes as a result of oceanic subduction followed by ...continental collision from Paleozoic to Mesozoic. In this paper we provide a synthesis of tectonic evolution, magmatism and metallogeny in the region based on data from literatures. Early Paleozoic ophiolites (473–439Ma) in the Changning–Menglian belt indicate the existence of a Proto-Tethys ocean in this region. Two episodes of subduction-related magmatism in the early-Paleozoic, one occurred in the Baoshan and Tengchong blocks at 502–455Ma and the other occurred in the Simao block at 421–401Ma, are regarded as evidence for two different events of subduction of the Proto-Tethys ocean at different locations. The Proto-Tethys was succeeded in early-Devonian by the Paleo-Tethys which comprised the main ocean and three branches: Ailaoshan, Jinshajiang and Garzê–Litang. The Changning–Menglian main ocean existed from middle-Devonian to middle-Triassic. The remnants of the oceanic crust are preserved in a few places in the Longmu Tso–Shuanghu suture as well as in the Changning–Menglian ophiolite belt. The eastward subduction of the main oceanic plate from early-Permian to early-Triassic formed a prominent arc terrane stretching >1500km from Yunnan to eastern Tibet. From the waning stage of subduction to post-subduction, numerous S-type granite plutons with ages varying between 230 and 219Ma, such as the Lincang batholith in Yunnan were emplaced at or close to the suture. This event produced several hydrothermal W–Sn deposits in the region. The tectonic evolution and associated magmatism of the Jinshajiang and Ailaoshan branch oceans are generally comparable to those of the main ocean. However, the branch oceans were subducted westward instead. The Garzê–Litang branch ocean also underwent westward subduction from middle-Devonian to late-Triassic. Arc-related high Sr/Y porphyry intrusions and associated porphyry-skarn Cu–Mo–Au deposits are common in the Jinshajiang–Ailaoshan region, especially in the Yidun arc which formed prior to Jurassic. The VMS deposits in the Sanjiang region formed in diverse tectonic settings including middle-Silurian back-arc basins, Carboniferous oceanic islands, Paleozoic subduction zones and Triassic post-subduction rifting environments. The Mesozoic and early-Cenozoic evolution of the Baoshan and Tengchong blocks was largely influenced by eastward oceanic subduction of the Meso- and Neo-Tethys from late-Permian to middle-Cretaceous and from late-Cretaceous to ~50Ma, respectively. Abundant early-Cretaceous granitoids and associated skarn-type Pb–Zn and Sn–Fe deposits in the Baoshan and Tengchong blocks were produced in the background of the Shan boundary oceanic slab subduction to the west and the break-off of the Nujiang-Bitu oceanic slab to the north. The subduction of the Neo-Tethys oceanic plate beneath the Tengchong block from Late Cretaceous to Paleogene formed abundant S-type granitoids and many skarn-type and greisen-type Sn–W deposits. Granitoids formed at 105 to 81Ma and contemporaneous hydrothermal W, Mo, Ag and Au deposits, which temporally coincided with the subduction of the Neo-Tethys, are common in the Yidun arc terrane.
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The Sanjiang Tethyan Orogen (SJTO) of the eastern Tethyan tectonic belt in China records a transition from Late Paleozoic Tethys realm to Cenozoic continental collision associated with the formation ...of large metallic mineral deposits. This contribution combines geological and Hf-isotopic data for igneous rocks from the SJTO, together with the salient features associated with mineralization to gain insights into the crustal architecture and metallogeny. Integrating the available information from tectonic events, sedimentary successions, paleobiogeography, and paleolatitude based on paleomagnetic data, the Hf isotopic maps that we construct highlight the Changning–Menglian Suture as an important tectonic boundary between the Gondwana and Cathaysian continents. The Changning–Menglian Suture separates two distinct Hf isotopic domains with an old, reworked, crustal block to the southwestern part of the SJTO, and a juvenile crustal block with significant mantle-derived components to the northeastern part of the orogen.
The Hf isotopic mapping of the SJTO also provides important indications on the location of different deposits. The Jinshajiang–Ailaoshan Suture appears to have exerted a first-order control on the localisation of Cenozoic magmatism and intrusion-related mineral systems. The magmatic source for intrusions in the eastern high-εHf, low TDMc domain, is dominated by mantle components and gave rise to porphyry and porphyry–skarn Cu–(Mo) mineralization. In contrast, the magma sources for intrusions in the low-εHf, high TDMc domains contain an old and reworked crustal component and gave rise to granite-related Sn–W mineralization. Those for the intrusions characterized by variable εHf and TDMc are dominantly reworked older crustal components together with subordinate juvenile material which generated the granite-related Pb–Zn–Cu–Ag mineralization.
The Eastern Qinling Orogen (EQO) is a major composite collisional zone located between the North China and the Yangtze cratons. This contribution combines geological and Hf–isotopic data from ...magmatic rocks associated with mineralization to gain insights into links between the crust architecture and metallogeny, and to focus exploration in the orogen.
The new zircon U–Pb dates reported in this study are 434±2Ma for diorite, 433±2 and 436±2Ma for monzogranite, and 454±2Ma for granodiorite in the Nanzhao area; 225±2Ma for syenite and 160±1Ma for monzogranite at Songxian; and 108±1 and 102±1Ma for syenogranite in eastern Fangcheng. Combining our data with those from the entire EQO reveals seven major magmatic events since the Cambrian. These magmatic events took place during the Cambrian–Silurian associated with subduction, Early Devonian magmatism related to a collisional event, Early Permian to Late Triassic magmatism related to subduction, Late Triassic collisional magmatism, Late Triassic to Early Jurassic post–collision magmatism, and Jurassic–Cretaceous magmatism during intra–continental subduction.
Lu-Hf isotopic data collected from granitic rocks for this study give εHf(t) values of: −1.4 to 10.9 for diorite and monzogranite at Nanzhao; −27.1 to −15.6 for syenite and −27.5 to −25.1 for monzogranite at Songxian; and −12.9 to −3.4 for syenogranite in the eastern Fangcheng. Combining Hf isotopic data for the EQO from previous studies, we have evaluated the spatio–temporal distribution of Hf isotopic compositions. The resultant Hf isotopic maps highlight the location of the Kuanping Suture as an important tectonic boundary between the North China and the Yangtze cratons, which separates the EQO into a north part with an old and reworked lower crust and a southern part representing a juvenile lower crust.
The Hf isotopic mapping of the EQO also provides information on the distribution of mineral deposits. Porphyry and porphyry–skarn Mo(–W) deposits are associated with magmatic rocks were emplaced in zones with low–εHf and high TDMc values representing old and reworked crustal components. In contrast, porphyry and porphyry–skarn Cu(–Mo) deposits are associated with magmatic rocks emplaced in domains with variable εHf and TDMc values characterized by dominantly reworked old crustal components with minor juvenile material. The magmatic source for the intrusions is characterized by low–εHf and high TDMc values, which are granite–related Mo or Pb–Zn–Ag mineralization.
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•Hf isotopic mapping reveals tectonic boundary between the NCC and Yangtze Craton.•Hf isotopic mapping reveals crustal architecture in the EQO.•Hf isotopes and older model ages reflect old-reworked crustal terrane to the north.•Hf isotopes and younger model ages reflect juvenile crustal terrane to the south.•Hf isotopic mapping builds link between deposit and Hf isotopic composition.
Tin mineralization in the southwestern Sanjiang Tethys Sn metallogenic domain extends from the Southeast Asia tin belt in the south. The eastern part of the domain does not contain significant Sn ...deposits, whereas the central part of the domain, composed of the Changning–Menglian Sn belt and related to ca. 239–178Ma S-type granitoids generated by the collision between Tengchong–Baoshan and Simao Blocks carries widespread the hydrothermal vein type mineralization. The western part of the domain, composed of the Tengchong–Baoshan Sn metallogenic belt, is related to both 136–113Ma and 89–52Ma S-type granitoids. The former granitoids resulted from the collision between Western Burma and Tengchong–Baoshan Blocks, and generated skarn-type tin deposits. The younger groups correspond to the India–Asia continental collision and are associated with the Xiaolonghe and Lailishan greisen type Sn deposits.
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•The Permian Lincang granitoids reveal the eastward subduction of the Paleo-Tethys.•The Late Triassic–Early Cretaceous granitoids are related to crustal partial melting.•The Late Cretaceous–Early Cenozoic granitoids resulted from the continental collision.•This paper reveals tin metallogenesis in the southwest Sanjiang Tethys.
The Jiaojia Fault (JJF) in the Jiaodong area of eastern China is an important NNE-trending structure that is subsidiary to the regional Tancheng–Lujiang (Tan-Lu) Fault Zone, and hosts >1200 t of gold ...reserves contained in disseminated and stockwork ore, dominantly in the footwall of the fault. We present new zircon U–Pb, apatite fission track, and illite K–Ar data along the JJF and have delineated its tectonic history focusing on its formation and reactivation. Zircon U–Pb dating shows that the Shangzhuang granite is a composite body with ages between 132 ± 1 and 127 ± 1 Ma. Illite K–Ar ages for the fault’s gouge range from 83 ± 2 to 68 ± 2 Ma, and the measured apatite fission track ages for ores are between 55 and 21 Ma. Previous zircon U–Pb geochronology and structural studies suggest that the JJF was originally activated in the Jurassic during 160–150 Ma as a sinistral fault. The JJF was a normal fault in the Early Cretaceous due to NW–SE orientated tension and NE–SW compression, which lasted from 135 to 120 Ma. This was followed by sinistral strike–slip faulting due to NW–SE compression and NE–SW tension during 120–110 Ma, and it changed to normal displacement at ca. 110 Ma. Our apatite fission track data analysis and thermal modeling of representative samples suggest that there was a subsequent dextral reactivation of the fault at ca. 55 Ma. Previous age data of ca. 130–110 Ma for gold mineralization along the JJF coincides with the Early Cretaceous magmatism and is coeval with the transition from normal faulting to sinistral strike–slip faulting of the JJF in Early Cretaceous, which is interpreted to be due to changing direction of the subducting Pacific Plate.
In China, sediment-hosted Pb―Zn deposits represent a significant type of base-metal deposits are major sources of Pb and Zn and significant sources of Ag and Ge. In this paper, we focus discussion on ...MVT (Mississippi Valley type), SEDEX (sedimentary exhalative) and Jinding-type deposits because they constitute the major subtypes of sediment-hosted Pb―Zn deposits in China. For these deposits, which occur in a wide variety of carbonate and siliciclastic rocks having no obvious genetic association with igneous activity, we present an overview and re-evaluation with regard to: (1) nature, diversity, and geological settings, (2) spatio-temporal distributions, (3) structural controls on mineralization, (4) metallogenic process, and (5) C, O, S and Pb isotope geochemistry. Several of these deposits with known reserves are concentrated in eight main metallogenic belts. Available data from these deposits in China show the highest combined Zn and Pb reserves exist in the Qinling Mountains metallogenic belt, followed by the northern margin of the North China Craton (NCC), the Sanjiang fold belt, the Upper Yangtze River belt, the South China fold system, the Tianshan–Beishan Mountains belt, the Lower Yangtze River belt, and the Qilian Mountains belt. In these belts, the sediment-hosted Pb―Zn deposits have formed in a variety of tectonic settings representing a range of processes that have occurred within two billion years of earth history, but large-scale mineralizations have occurred notably in the Proterozoic, Late Paleozoic and Cenozoic. The Proterozoic era was important for the formation of SEDEX Pb―Zn deposits such as those in the interior and along the edges of the NCC and Yangtze Craton. The Guanmenshan is the only known MVT deposit formed within an intra-continental basin in the Proterozoic era. The Late Paleozoic was a productive period for MVT Pb―Zn deposits in China; in particular, there were significant MVT mineralizations during Devonian to Permian as a result of the amalgamation of the NCC and the South China Craton. The Cenozoic was a significant metallogenic era in China. For example, in the Sanjiang area during the Cenozoic, the Lanping Basin has evolved from a passive margin to open ocean basin and then has experienced ocean basin closure followed by the India–Asia collision and related tectonic activities including thrusting, and formation of strike–slip extensional basins, in which the Jinding-type deposits developed.
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•Nature and diversity of sediment-hosted Pb―Zn deposits were summarized.•Temporal–spatial distributions of sediment-hosted Pb―Zn deposits were built.•Geological settings, structural controls of sediment-hosted Pb―Zn deposits were studied.•Metallogenic process of sediment-hosted Pb―Zn deposits was analyzed.•C, O, S and Pb isotope geochemistry of sediment-hosted Pb―Zn deposits were summarized.
•These dykes constrain opening and closing ages of the Xiong’er rift.•These dykes are remarkable evidence for the evolution of the North China Craton.•These dykes provide important evidence for ...breakup of the supercontinent Columbia.
The Xiong’er rift zone along the southern margin of the North China Craton (NCC) is characterized by exposure of a suite of volcanic rocks and associated mafic – intermediate dykes and sedimentary rocks. In this study, we report for the first time the newly identified late Paleoproterozoic diorite dykes from the Waifangshan Mountain in the Xiong’er rift zone and present results from the LA-ICP-MS zircon U–Pb dating, Sr–Nd–Hf isotope systematics, and whole-rock major and trace element geochemistry. The Wafang diorite dykes intruding into the upper part of the Xiong’er Group yielded emplacement mean ages of 207Pb/206Pb from 1746±22Ma to 1762±11Ma. These diorite dykes have extreme low MgO, Cr and Ni contents, and enriched in LREEs and LILEs but depleted in HFSEs (Nb, Ta, and Ti). They are characterized by having negative zircon ɛHf(t) values of −11.4 to −3.1, a whole-rock initial 87Sr/86Sr value of 0.70196 and ɛNd(t) value of −8.7, and Pb isotopes (206Pb/204Pb=16.072–16.295, 207Pb/204Pb=15.275–15.293, 208Pb/204Pb=36.538–37.255). These geochemical features, together with trace element modeling, suggest that the late Paleoproterozoic Wafang diorite dykes could be sourced from crustal melting with minor contribution of the mixing of mantle materials. These new data combined with previous studies on the late Paleoproterozoic the Xiong’er volcanism should have lasted for nearly 43Ma ranging from 1789Ma to 1746Ma. Correspondingly, the initiation timing of the Xiong’er rift should be younger than 1831Ma, but earlier than 1625. The Wafang diorite dykes formed in a rift environment, possibly related to breakup of the supercontinent Columbia.
The volcanic rocks of the Xiong'er Group are situated in the southern margin of the North China Craton (NCC). Research on the Xiong'er Group is important to understand the tectonic evolution of the ...NCC and the Columbia supercontinent during the Paleoproterozoic. In this study, to constrain the age of the Xiong'er volcanic rocks and identify its tectonic environment, we report zircon LA-ICP-MS data with Hf isotope, whole-rock major and trace element compositions and Sr–Nd–Pb–Hf isotopes of the volcanic rocks of the Xiong'er Group. The Xiong'er volcanic rocks mainly consist of basaltic andesite, andesite, dacite and rhyolite, with minor basalt. Our new sets of data combined with those from previous studies indicate that Xiong'er volcanism should have lasted from 1827 Ma to 1746 Ma as the major phase of the volcanism. These volcanics have extremely low MgO, Cr and Ni contents, are enriched in LREEs and LILEs but depleted in HFSEs (Nb, Ta, and Ti), similar to arc-related volcanic rocks. They are characterized by negative zircon εHf(t) values of −17.4 to −8.8, whole-rock initial 87Sr/86Sr values of 0.7023 to 0.7177 and εNd(t) values of −10.9 to −6.4, and Pb isotopes (206Pb/204Pb = 14.366–16.431, 207Pb/204Pb = 15.106–15.371, 208Pb/204Pb = 32.455–37.422). The available elemental and Sr–Nd–Pb–Hf isotope data suggest that the Xiong'er volcanic rocks were sourced from a mantle contaminated by continental crust. The volcanic rocks of the Xiong'er Group might have been generated by high-degree partial melting of a lithospheric mantle that was originally modified by oceanic subduction in the Archean. Thus, we suggest that the subduction-modified lithospheric mantle occurred in an extensional setting during the breakup of the Columbia supercontinent in the Late Paleoproterozoic, rather than in an arc setting.
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•The Xiong'er volcanic rocks constrain evolution of the Xiong'er rift.•The Xiong'er volcanic rocks are remarkable evidence for evolution of the North China Craton.•The Xiong'er volcanic rocks provide evidence for breakup of the supercontinent Columbia.
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