Thermotectonic evolution of the Paleozoic granites along the Shangdan suture zone (central China): Crustal growth and differentiation by magma underplating in an orogenic belt

2020 ◽  
Author(s):  
Jiang-Feng Qin ◽  
Shao-Cong Lai ◽  
Xiao-Ping Long ◽  
Ze-Zhong Zhang ◽  
Yin-Juan Ju ◽  
...  
Keyword(s):  
High Temperature ◽  
Tectonic Setting ◽  
Orogenic Belt ◽  
Source Rocks ◽  
Central China ◽  
Moderate Pressure ◽  
Crustal Growth ◽  
Geochemical Properties ◽  
T Values ◽  
Zircon Saturation

The nature of source rocks and the pressure-temperature-hydration (P-T-H2O) condition are the two main factors that control the geochemical properties of granites. Therefore, the evolution of P-T-H2O conditions can be used to deduce the tectonic setting of granites. In this paper, we report on three Paleozoic granite plutons along the Shangdan suture that revealed increasing melting temperature and decreasing pressure from 437 to 403 Ma, suggesting a crustal thinning process. The Tieyupu granodiorites (437 ± 4 Ma) display Na-rich adakite affinity, i.e., SiO2 = 69.1−70.1 wt%, Na2O/K2O = 1.9−2.26, positive zircon εHf(t) values (+4.29 to +12.04), and high Sr/Y (137−160) and Y/Yb (9.89−10.25) ratios, implying a garnet-rich residue in their source. In combination with moderate zircon saturation temperatures (814−822 °C), we infer that the Tieyupu granodiorites were formed by melting of Neoproterozoic metabasites under high-pressure (>1.5 GPa) and moderate-temperature (HP-MT) conditions. The Liangchahe granodiorites (415 ± 8 Ma) also display Na-rich adakite affinity, i.e., higher Na2O/K2O (2.16−3.11) and lower Sr/Y (77−88) ratios, and higher zircon saturation temperatures (854−874 °C), and they are interpreted to have been derived from melting of metabasites under moderate-pressure (>1.0 GPa) and high-temperature (MP-HT) conditions. Their variable zircon εHf(t) values (−14.97 to +9.80) and the existence of zircon xenocrysts suggest that the primitive adakitic melts were assimilated by evolved crustal components. The Yaogou monzogranites (403 ± 4 Ma) have the highest K2O/Na2O (0.81−1.00) ratios and total rare earth element (ΣREE; 105−191 ppm) contents, lowest Sr/Y (14−43) ratios, positive zircon εHf(t) values (+6.79 to +12.22), and highest zircon saturation temperatures (891−973 °C), showing they were formed by high-temperature melting of intermediate rocks under low-pressure conditions (<1.0 GPa). The evolution of P-T conditions revealed by these three granites suggests that crustal growth and differentiation were related to gradual extensional and melting of mafic protoliths in the orogenic belt.

Duobagou Permian–Triassic granites from the Dunhuang orogenic belt, NW China: implications for the tectonic evolution of the southernmost Central Asian Orogenic Belt

2020 ◽  
pp. 1-17
Author(s):  
Zhendong Wang ◽  
Yuanyuan Zhang ◽  
Xiangjiang Yu ◽  
Zhaojie Guo
Keyword(s):  
Partial Melting ◽  
Tectonic Evolution ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Crustal Growth ◽  
Central Asian ◽  
Granitic Intrusions ◽  
Mantle Component ◽  
Type Granite ◽  
T Values

Abstract The Duobagou Permian–Triassic granites of the Dunhuang orogenic belt are of great importance in understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt. LA-ICP-MS U–Pb zircon ages indicate that Permian–Triassic granitic intrusions from the Duobagou area formed at 276–274 Ma and 246 ± 1 Ma. These granites have high SiO2, Na2O and K2O, but low Al2O3, CaO and MgO contents and belong mainly to the high-K calc-alkaline I-type granite series. Based on whole-rock geochemistry and Sr–Nd and zircon Hf isotopes, the Duobagou Permian–Triassic granites were dominantly derived from the partial melting of lower continental crust formed during late Palaeoproterozoic to Mesoproterozoic times in a post-collisional extensional setting. Permian granites with zircon ϵHf(t) values of −5.4 to +3.1 and Hf model ages of TDM2 = 1.14–1.70 Ga indicate the involvement of a mantle component in their petrogenesis. Triassic granites with higher zircon ϵHf(t) values (+0.5 to +3.8) and TDM2 = 1.08–1.31 Ga suggest more juvenile sources caused by a greater contribution of mantle-derived melts, indicating a significant crustal growth. Regional extension from lithospheric delamination and heating from asthenospheric upwelling were proposed to have triggered the partial melting of lower crust, resulting in the generation of the Permian–Triassic magmatism. This may have been the mechanism for the significant crustal growth during Permian and Triassic times in the southernmost Central Asian Orogenic Belt.

Granitoids of the Central Asian Orogenic Belt and continental growth in the Phanerozoic

2000 ◽  
Vol 91 (1-2) ◽  
pp. 181-193 ◽  
Author(s):  
Bor-ming Jahn ◽  
Fuyuan Wu ◽  
Bin Chen
Keyword(s):  
Central Asia ◽  
Basaltic Magma ◽  
Orogenic Belt ◽  
Source Rocks ◽  
Central Asian Orogenic Belt ◽  
Central Asian ◽  
Wide Range ◽  
Mantle Component ◽  
T Values ◽  
Lower Crustal

The Central Asian Orogenic Belt (CAOB), also known as the Altaid Tectonic Collage, is characterised by a vast distribution of Paleozoic and Mesozoic granitic intrusions. The granitoids have a wide range of compositions and roughly show a temporal evolution from calcalkaline to alkaline to peralkaline series. The emplacement times for most granitic plutons fall between 500 Ma and 100 Ma, but only a small proportion of plutons have been precisely dated. The Nd-Sr isotopic compositions of these granitoids suggest their juvenile characteristics, hence implying a massive addition of new continental crust in the Phanerozoic. In this paper we document the available isotopic data to support this conclusion.Most Phanerozoic granitoids of Central Asia are characterised by low initial Sr isotopic ratios, positive εNd(T) values and young Sm—Nd model ages (TDM) of 300-1200 Ma. This is in strong contrast with the coeval granitoids emplaced in the European Caledonides and Hercynides. The isotope data indicate their ‘juvenile’ character and suggest their derivation from source rocks or magmas separated shortly before from the upper mantle. Granitoids with negative εNd(T) values also exist, but they occur in the environs of Precambrian microcontinental blocks and their isotope compositions may reflect contamination by the older crust in the magma generation processes.The evolution of the CAOB is probably related to accretion of young arc complexes and old terranes (microcontinents). However, the emplacement of large volumes of post-tectonic granites requires another mechanism, probably through a series of processes including underplating of massive basaltic magma, intercalation of basaltic magma with lower crustal granulites, partial melting of the mixed lithologic assemblages leading to generation of granitic liquids, followed by extensive fractional crystallisation. The proportions of the juvenile or mantle component for most granitoids of Central Asia are estimated to vary from 70% to 100%.

scholarly journals Geochemistry of the Paleocene Clastic Rocks From the Southwestern Jianghan Basin, Central China Reveal Their Provenance, Tectonic Setting, and Palaeoenvironment

2021 ◽  
Author(s):  
Kai Yan ◽  
Chun-lian Wang ◽  
Jiu-yi Wang ◽  
Xiao-can Yu ◽  
Xiao-hua Teng ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Active Continental Margin ◽  
Source Area ◽  
Source Rocks ◽  
Central China ◽  
Clastic Rocks ◽  
Ree Distribution ◽  
C Value ◽  
Tectonic Settings ◽  
Jianghan Basin

Abstract This paper intends to learn about the provenance, tectonic setting and paleoenvironment of the Paleocene Shashi Formation in the southern Jianghan Basin by the bulk-rock geochemistry. The K2O/Al2O3 and SiO2/Al2O3 ratios indicate that the major proportion of samples are litharenite. The chondrite-normalized REE distribution pattern of the Shashi Formation’s mudstones are characterized by enriched LREE and flat HREE similar to those of UC with negative Eu anomalies. Combined with the geochemical element ratio discriminant diagram, such as Al2O3-TiO2, Zr-TiO2, La/Sc-Co/Th, and Hf-La/Th, so on, these samples were sourced from mixed felsic/basic rock. Moreover, the discriminant diagrams of K2O/Na2O-SiO2/Al2O3, La-Th-Sc, and Th-Co-Zr/10 suggest that the samples were formed under the tectonic settings of active continental margin and continental island arc. The values of CIA, CIW, PIA, ICV, Zr/Sc-Th/Sc, and ternary diagrams of A-(CN)-K and Al2O3-Zr-TiO2 indicate that weathering in the source area was weak and source rocks have not been reformed by depositional recirculation and hydraulic sorting. And the palaeoenvironmental indicators of C-value, Ni/Co, V/Cr, V/(V+Ni) and Sr/Cu, Ga/Rb indicate that the climate was cool and arid during the evaporite deposition period in the southern Jianghan Basin, and the water was in the condition of oxidation.

scholarly journals Crustal growth and reworking: A case study from the Erguna Massif, eastern Central Asian Orogenic Belt

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Chenyang Sun ◽  
Wenliang Xu ◽  
Peter A. Cawood ◽  
Jie Tang ◽  
Shuo Zhao ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Crustal Growth ◽  
Central Asian ◽  
Mesozoic Granitoids ◽  
Tectonic Settings ◽  
Crustal Heterogeneity ◽  
Erguna Massif ◽  
T Values

AbstractDespite being the largest accretionary orogen on Earth, the record of crustal growth and reworking of individual microcontinental massifs within the Central Asian Orogenic Belt (CAOB) remain poorly constrained. Here, we focus on zircon records from granitoids in the Erguna Massif to discuss its crustal evolution through time. Proterozoic–Mesozoic granitoids are widespread in the Erguna Massif, and spatiotemporal variations in their zircon εHf(t) values and TDM2(Hf) ages reveal the crustal heterogeneity of the massif. Crustal growth curve demonstrates that the initial crust formed in the Mesoarchean, and shows a step-like pattern with three growth periods: 2.9–2.7, 2.1–1.9, and 1.7–0.5 Ga. This suggests that microcontinental massifs in the eastern CAOB have Precambrian basement, contradicting the hypothesis of significant crustal growth during the Phanerozoic. Phases of growth are constrained by multiple tectonic settings related to supercontinent development. Calculated reworked crustal proportions and the reworking curve indicate four reworking periods at 1.86–1.78 Ga, 860–720 Ma, 500–440 Ma, and 300–120 Ma, which limited the growth rate. These periods of reworking account for the crustal heterogeneity of the Erguna Massif.

Provenance and tectonic setting of the Upper Palaeozoic sandstones in western Inner Mongolia (the Shalazhashan and Solonker belts), China: insights from detrital zircon U–Pb ages and Hf isotopes

2017 ◽  
Vol 156 (3) ◽  
pp. 547-571 ◽  
Author(s):  
GUANZHONG SHI ◽  
GUANGZENG SONG ◽  
HUA WANG ◽  
CHUANYAN HUANG ◽  
BEN LI
Keyword(s):  
Tectonic Setting ◽  
Sedimentary Environment ◽  
Depositional Environments ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Provenance Analysis ◽  
Northern Margin ◽  
Isotopic Analyses ◽  
Early Palaeozoic ◽  
T Values

AbstractThe Solonker and Shalazhashan belts are hotly debated tectonic units of the Central Asian Orogenic Belt (CAOB), because they may either represent a Permian or Triassic suture zone of the CAOB, or a rifting zone overprinted on an Early Palaeozoic orogen. Provenance analysis of the Upper Palaeozoic sandstones in these belts may provide useful constraints on this issue. This study collected six sandstone samples from three study areas: the Mandula area of the Solonker Belt, the Quagan Qulu area of the Shalazhashan Belt but close to the Alxa block, and the Enger Us area of the Shalazhashan Belt, for framework petrography, zircon morphology, U–Pb and Lu–Hf isotopic analyses. Framework petrography reveals that the Mandula and Enger Us area samples contain high proportions of volcanic fragments, whereas the samples from the Quagan Qulu area include not only volcanic fragments but also significant amounts of biotite and muscovite. The detrital zircons of the Mandula area and the Enger Us area yield two main age groups: (i) 260–330 Ma, with dominant εHf(t) values of –5 to +12; and (ii) 420–550 Ma, with dominant εHf(t) values of –9 to +9, suggesting that Early Palaeozoic arc-related magmatic rocks and Late Palaeozoic syn-depositional volcanic rocks are the main source rocks. The detrital zircons of the Quagan Qulu area have one main age group of 420–500 Ma and some grains of 0.9–1.1 Ga, 1.4–1.5 Ga, 1.8–1.9 Ga and ~ 2.5 Ga, which derive from the northern margin of the Alxa block. The lithological and fossil assemblages of the Upper Palaeozoic sandstones suggest shallow-marine to deep-water depositional environments and a northward-deepening transition. Based on the zircon spectra, sedimentary environment analysis and previous studies, we argue that the Solonker Belt and the Shalazhashan Belt of the CAOB are in extensional basins of a fore-arc or rifting setting.

scholarly journals Supplemental Material: Thermotectonic evolution of the Paleozoic granites along the Shangdan suture zone (central China): Crustal growth and differentiation by magma underplating in an orogenic belt

2020 ◽  
Author(s):  
Jiang-Feng Qin
Keyword(s):  
Trace Element ◽  
Mineral Chemistry ◽  
Suture Zone ◽  
Orogenic Belt ◽  
Central China ◽  
Crustal Growth ◽  
Nd Isotope

Table S1: mineral chemistry; Table S2: zircon U-Pb age; Table S3: major-trace element; Table S4: Sr-Nd isotope; Table S5: zircon Lu-Hf; Table S6: zircon log fO2 value; Table S7: summarize table.

Provenance and tectonic setting of late Paleozoic sedimentary rocks from the Alxa Tectonic Belt (NW China): Implications for accretionary tectonics of the southern Central Asian Orogenic Belt

2020 ◽  
Vol 133 (1-2) ◽  
pp. 253-276
Author(s):  
Dongfang Song ◽  
Wenjiao Xiao ◽  
Brian F. Windley ◽  
Chunming Han
Keyword(s):  
Tectonic Setting ◽  
Sedimentary Rocks ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Late Paleozoic ◽  
Early Triassic ◽  
Central Asian ◽  
Southern Central ◽  
T Values ◽  
Tectonic Belt

Abstract The Central Asian Orogenic Belt has long been considered the largest Phanerozoic accretionary orogen in the world; it developed through the subduction and final closure of the Paleo–Asian Ocean. However, the architecture and duration of the accretionary orogenesis of the Central Asian Orogenic Belt are still controversial despite decades of investigation. In this study, we present field, compositional, and stratigraphically controlled detrital zircon geochronological data for late Paleozoic sedimentary rocks from the Alxa Tectonic Belt to constrain their provenance, tectonic setting, and the overall tectonic configuration of the southern Central Asian Orogenic Belt. A Devonian sample yields a unimodal age peak (ca. 424 Ma) and broad late Mesoproterozoic ages. A Carboniferous sample has Early Silurian (ca. 438 Ma) and Late Devonian (ca. 382 Ma) peaks along with Neoproterozoic to Archean ages. The Permian samples are dominated by Ordovician–Devonian and Carboniferous–Permian ages. They yield maximum depositional ages ranging from ca. 291 Ma to 248 Ma and contain abundant zircon ages that are close to their depositional ages. These data reveal Ordovician–Silurian and Carboniferous–Permian magmatic flare-ups separated by a Devonian magmatic lull in the southern Central Asian Orogenic Belt. The arc terranes in southern Mongolia, central Beishan, and northern Alxa provided major detritus for the late Paleozoic sediments. An abrupt shift of zircon εHf(t) values at ca. 400 Ma reveals significant late Paleozoic crustal growth and excludes southern Alxa as a source. Oceanic basins prevented detritus from southern Alxa from reaching northern Alxa during Permian–Early Triassic time. A geological and provenance comparison of Permian basins in the southern Central Asian Orogenic Belt reveals the existence of two separate forearcs ascribed to bipolar subduction of the Paleo–Asian Ocean. Combined with recent paleomagnetic data, this leads us to advocate for an archipelago-style accretionary process induced by subduction retreat for the late Paleozoic tectonic evolution of the southern Central Asian Orogenic Belt, which continued into Late Permian–Early Triassic.

Petrography and geochemistry of the Lower Silurian sandstones from the Angzanggou Formation in the North Qilian Belt, China: implications for provenance, weathering and tectonic setting

2019 ◽  
Vol 157 (3) ◽  
pp. 477-496
Author(s):  
Qian Hou ◽  
Chuanlong Mou ◽  
Zuozhen Han ◽  
Qiyu Wang ◽  
Zhiyuan Tan ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Tectonic Setting ◽  
Orogenic Belt ◽  
Source Rocks ◽  
Petrographic Analysis ◽  
The Tibetan Plateau ◽  
Lower Silurian ◽  
The North ◽  
North Qilian Orogenic Belt ◽  
North Qilian

AbstractThe North Qilian Orogenic Belt is on the northeastern margin of the Tibetan Plateau. It is connected with the Alxa Block in the north and the Tethyan orogenic assemblage in the south. The Lower Silurian Angzanggou Formation, deposited in the northern area of the North Qilian Orogenic Belt, is the most important for revealing the architecture and orogenic processes of the North Qilian Belt. Provenance analysis of the Angzanggou Formation can reveal not only the tectonic evolution of the central orogenic belt of China but also Palaeozoic Asia plate reconstructions. Petrographic analysis indicated that the compositional and textural maturity of the sandstones was low. The detrital composition of the Angzanggou Formation samples consists of quartz (8–14 %), feldspar (6–29 %) and lithic fragments (56–86 %). The sandstones could be classified as litharenites or feldspathic litharenites. The detrital modal composition suggests that these sandstones were probably deposited in a fore-arc basin. The element ratios and some discrimination diagrams based on geochemistry indicate that felsic and intermediate rocks were the main source rocks. The SiO2/Al2O3 ratio, the index of chemical variability and the Th/Sc versus Zr/Sc discrimination diagram suggest that the compositional maturity and degree of recycling were moderate to low. The index of alteration (CIA) and the A–CN–K diagram indicate the intensity of weathering was moderate. The discrimination diagrams based on major and trace elements and petrographic discrimination diagrams imply that the Angzanggou Formation rocks were derived from a continental island arc, and a sedimentary cover probably overlaid the volcanic arc. Therefore, we infer that during Early Silurian time the North Qilian Belt sediments accumulated in a fore-arc basin.

scholarly journals Supplemental Material: Thermotectonic evolution of the Paleozoic granites along the Shangdan suture zone (central China): Crustal growth and differentiation by magma underplating in an orogenic belt

2020 ◽  
Author(s):  
Jiang-Feng Qin
Keyword(s):  
Trace Element ◽  
Mineral Chemistry ◽  
Suture Zone ◽  
Orogenic Belt ◽  
Central China ◽  
Crustal Growth ◽  
Nd Isotope

Table S1: mineral chemistry; Table S2: zircon U-Pb age; Table S3: major-trace element; Table S4: Sr-Nd isotope; Table S5: zircon Lu-Hf; Table S6: zircon log fO2 value; Table S7: summarize table.

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