Early Cretaceous Volcanic Rocks Research Articles

Petrogenesis of Early Cretaceous volcanic rocks in the southeastern margin of the Songliao Basin, NE China: implications for the geodynamic evolution of Paleo-Pacific Ocean

Petrogenesis of Early Cretaceous volcanic rocks in the southeastern margin of the Songliao Basin, NE China: implications for the geodynamic evolution of Paleo-Pacific Ocean

Early cretaceous volcanic rocks in Sandaowanzi area constrain the geodynamics and magma fertility

The complex and diversified geodynamic mechanism brought massive magmatic activity and gold mineralization in the early Cretaceous in the Great Xing'an Range. The Sandaowanzi gold deposit has a close temporal-spatial correlation with the early Cretaceous magmatism. However, the genetic relationship between the Early Cretaceous volcanic rocks and Sandaowanzi gold mineralization is not well constrained. In addition, the metallogenic geodynamic background of the Sandaowanzi gold deposit remains controversial. Here, the zircon U-Pb geochronology, zircon trace elements, in-situ zircon Hf isotopes, and whole-rock geochemistry of the Sandaowanzi ore-hosting volcanic rocks are reported. The Sandaowanzi volcanic rocks, including andesite and dacite, show variable contents of MgO, Cr, Ni, and adakitic affinity, and are proposed to originate from delaminated lower crust that interacted with lithospheric mantle metasomatized by subduction-related sediments. Besides, it may have experienced fractional crystallization of olivine, clinopyroxene, and amphibole during the early stage of magmatic evolution. Their petrogenesis, combined with other geological evidence, indicates that the Sandaowanzi volcanic rocks were formed during the slab rollback process of the Paleo-Pacific Ocean. Finally, the elemental and isotopic signatures of zircons in the Sandaowanzi magmatic rocks imply that magmas with high water content, high oxygen fugacity, and a high proportion of mantle material contribution produced during 121–123 Ma have the highest mineralization potential, which is consistent with the Rb-Sr isochron ages of ore minerals. The geochemical characteristics of zircons from magmatic rocks in ore deposits provide effective indices for constraining the magma fertility.

Petrogenesis of Early Cretaceous volcanic rocks from the Rena-Co area in the southern Qiangtang Terrane, central Tibet: evidence from zircon U-Pb geochronology, petrochemistry and Sr-Nd-Pb–Hf isotope characteristics

AbstractThe subduction of the Bangong–Nujiang Ocean is important in the geological evolution of the Tibetan Plateau. In this paper, we report new zircon U-Pb age and Lu-Hf isotopic data and whole-rock elemental and Sr-Nd-Pb isotopic data for Early Cretaceous dacites from the Rena-Co area (RCA) in the southern Qiangtang Terrane (QT), central Tibet and use these data to better understand the tectonic evolution of the Bangong–Nujiang suture. LA–ICP-MS dating of zircons yields ages of 109.5 ± 0.6 Ma to 109.6 ± 0.8 Ma for the dacites from the RCA. Geochemically, these dacites are medium-K calc-alkaline and show high SiO2 contents of 64.79–70.37 wt.%, high Sr contents of 517–598 ppm and low Y contents of 8.45–10.7 ppm, similar to those of typical adakites. Additionally, all the rocks are strongly enriched in light rare earth elements and some large ion lithophile elements (e.g. Rb, U, K and Cs) but significantly depleted in high-field-strength elements (e.g. Nb, Ta and Ti), consistent with the geochemical characteristics of arc-type magmas formed in the subduction zone. Moreover, these adakite-like dacites show whole-rock initial (87Sr/86Sr)i ratios of 0.705119 to 0.705491, (206Pb/204Pb)i ratios of 18.489 to 18.508, (207Pb/204Pb)i ratios of 15.591 to 15.612, (208Pb/204Pb)i ratios of 38.599 to 38.686, ϵNd(t) values of −0.28 to +1.25 and single-stage Nd model ages of 642 to 818 Ma, as well as significantly positive zircon ϵHf(t) values of 3.9–13.1, with young Hf-depleted mantle ages of 331 to 923 Ma. These geochemical and isotopic data indicate that they are most likely derived from the juvenile thickened mafic lower continental crust, which contains partial melts of metasomatized peridotite and subduction-related fluids in the magma source region. Based on previous studies and our new data, we propose that the RCA adakite-like dacites are most likely a result of the northwards subduction of the Bangong–Nujiang Ocean lithosphere beneath the southern QT during the Early Cretaceous and that a slab rollback model could explain the formation of the RCA adakite-like dacites.

Petrogenesis of Early Cretaceous volcanic rocks in Santos Basin, offshore SE Brazil: evidence for the Tristan da Cunha plume

ABSTRACT The Santos Basin comprises the most voluminous hydrocarbon accumulations in its ‘Pre-salt’ reservoirs. Magmatic rocks have been recorded in the basin mostly by the tholeiitic basalts (Camboriú Formation) within its rift megasequence at Hauterivian time. Recent studies have shown that magmatic rocks are also found interbedded with Aptian sedimentary rocks in the basin, related to its post-rift (mostly Aptian) megasequence. This paper presents petrological data obtained from sidewall core samples of magmatic rocks interbedded with Early Aptian coquina in a well drilled in the Santos Basin. The well comprises six magmatic sections of alkaline basalts being overlain and underlain by the Barra Velha limestones. The basalts are mostly plagioclase-phyric, amygdaloidal rocks but vary in texture and modal compositions. Magmatic compositions seem to have been slightly affected by alteration processes. Basalts comprise an alkaline, miaskitic series with relatively evolved compositions (MgO = 5.55 ± 1.50 wt%; Ni < 220 ppm; Cr < 400 ppm). The patterns in the Primitive Mantle normalized multielement diagram displays the typical Nb peak (0.3 < La/Nb(N)<0.7) of the OIB. Geochemical modelling showed that basalts within five magmatic sections are not cogenetic by differentiation, representing basaltic flows emitted from different vents. Modal batch partial melting model indicates that it is possible, although unlikely, to generate the differences in La/Yb(N) and Zr/Y ratios of the least evolved samples in the studied well by different partial melting degrees (0.5–11%) from the same mantle source. Binary mixing models using lithogeochemical datapoint to a role for the Tristan da Cunha plume tail in the petrogenesis of the alkaline basalts with no clear evidence for a possible role for the local subcontinental lithospheric mantle. The results of the petrogenetic models are consistent with a shallow MOHO and a high-temperature mantle below part of the Santos Basin in Early Aptian time.

Geochronology and geochemistry of Early Cretaceous volcanic rocks in the Erlian Basin, NE China: implications for the late Mesozoic tectonic transformation of East Asia

ABSTRACT The formation and distribution of late Mesozoic volcanic rocks in northeast (NE) China remain unclear due to the superimposed influence of the tectonic regimes of the Mongol–Okhotsk Ocean (MOO) and Palaeo-Pacific Ocean (PPO) in Northeast Asia. This study reports the petrogenesis and tectonic settings of Early Cretaceous volcanic rocks from the Erlian Basin (EB) using petrology, geochronology, whole-rock geochemistry, and Sr–Nd–Hf isotopes. The U–Pb data for the magmatic zircons indicate that the volcanic rocks, including the trachytic rocks and rhyolites, erupted approximately at ~141–135 Ma. Trachytic rocks and rhyolites exhibit comparatively high SiO2 (58.74–65.77 wt. % and 71.35–72.99 wt. %, respectively) and alkali content, low Mg values (mean 25 and 24, respectively), and Cr, Co, and Ni contents, which differ from the geochemical characteristics of mantle-derived magmas. Furthermore, the positive ε Hf(t) (1.7–10.5) and ε Nd(t) (2.4–2.9) values of trachytic rocks and the positive ε Hf(t) values (4.3–6.6) of rhyolites indicate that these rocks were derived from the partial melting of the juvenile crustal materials. The relatively homogeneous zircon Hf isotopes and systematic variation of major and trace elements in these coeval volcanic rocks suggest that they have a common magma source and resulted from the development of the parent magma in the crustal magma chamber. Our results, combined with previous studies, demonstrate that Early Cretaceous volcanism in the EB records an extensional tectonic regime caused by lithospheric delamination after the closure of the MOO. During the Late Cretaceous, NE China was predominantly controlled by the PPO tectonic regime, accompanied by overall uplift and denudation of large-scale faulted basin groups.

Paleomagnetism and geochronology of Early Cretaceous volcanic rocks in the eastern segment of the Lhasa terrane, Tibetan Plateau, and their tectonic implications

Paleogeographic reconstructions of the Lhasa terrane for the Cretaceous provide important constraints on the evolution of the Neo-Tethys Ocean and crustal shortening within Asia. However, the Cretaceous paleogeography of the Lhasa terrane remains contentious. A direct way to study this issue is to conduct paleomagnetic investigations of the Cretaceous rocks of the Lhasa terrane; however, most previous Cretaceous paleomagnetic investigations of the Lhasa terrane were conducted in the middle and western segments of this terrane. Different vertical-axis rotations affected different parts of the Lhasa terrane following the India-Asia collision, and therefore paleomagnetic data from the western and middle segments of the Lhasa terrane cannot necessarily be used to directly constrain the paleolatitudes of its eastern segment. This study presents paleomagnetic data from the Early Cretaceous volcanic rocks with well-constrained ages from the Luolong area in the eastern segment of the Lhasa terrane. Isotope geochronology reveals that these rocks formed at 127−124 Ma. The mean high-temperature direction obtained from 17 paleomagnetic sites is declination/inclination (Ds/Is) = 21.8°/19.0° with κs = 65.8 and α95 = 4.4° (κ—best estimate of the precision parameter; α95—radius of the 95% probability ellipse around the mean direction; s—stratigraphic coordinates). Petrographic investigations, a positive fold test, a reversal test, and a paleosecular variation test indicate the primary origin of this characteristic remanence. A paleomagnetic pole of 60.9°N, 227.2°E with dp/dm = 2.4°/4.6° (dp/dm—semi-axes of the 95% probability ellipse around the mean pole) yields a paleolatitude of 9.2 ± 2.4°N for the eastern segment of the Lhasa terrane. Combined with reliable results from previous paleomagnetic studies, we draw the following conclusions. (1) During the Early Cretaceous, the Lhasa terrane was oriented WNW-ESE as a whole, and the eastern-middle segments may have been oriented nearly E-W. (2) Asia has accommodated 2050 ± 230 km of N-S crustal shortening along 96°E longitude since the Early Cretaceous. (3) The minimum N-S width of the Neo-Tethys Ocean at ca. 125 Ma was 4185 ± 300 km.

Zircon U–Pb–Hf Isotopes and Whole-rock Geochemistry of Rhyolite and Tuff from the Harachiyama Formation, North Kitakami Mountains, NE Japan

The Harachiyama Formation comprises Lower Cretaceous volcanic rocks, which are distributed in the eastern margin of the Kitakami Mountains in northeastern Japan. Whole-rock chemical analysis, U–Pb zircon dating and Hf isotope analysis of the Harachiyama Formation were performed to constrain the formation age and the magmatic origin was discussed. The lava and tuff samples of the Harachiyama Formation from the Omoto and Tsukue areas supported island-arc rhyolitic rocks (SiO2 content > 70%), and yielded the weighted mean U–Pb ages of 127.8 ± 3.4 Ma and 129.2 ± 2.6 Ma (2σ), respectively. Eighteen zircon grains from two samples, dated between 141.6 Ma and 123.9 Ma, yielded positive εHf(t) values between +5.0 and +8.7. The U–Pb ages and εHf(t) values are consistent with those of the Kitakami Granitoid reported in previous studies. Therefore, it is suggested that the Early Cretaceous volcanic rocks in northeastern Japan, such as the Harachiyama Formation, have the same magmatic origin as the Kitakami Granitoid.

Compositions and ages of Early Cretaceous volcanic and plutonic rocks in central Tibet: Insights into the magmatic and uplift response to slab breakoff

AbstractWe present new zircon U-Pb ages and Hf isotope compositions as well as whole-rock major- and trace-element geochemical and Sr-Nd isotopic data for silicic plutonic and volcanic rocks from the Duolong area of central Tibet. Combined with existing data, our new data indicate that these plutonic and volcanic rocks were formed in two stages ca. 120 Ma and ca. 110 Ma, respectively, in a postcollisional extensional setting that was triggered by slab breakoff. The similar geochemical compositions of granitoids and rhyolites, combined with their close spatial and temporal relationships, suggest that they were both derived from juvenile crustal material within a single magmatic system. We propose that the two inferred crustal melting events in the Duolong area were caused by two episodes of deep mantle activity triggered by the transition of the plate subduction angle from steep to shallow in response to the ascent of buoyant continental lithosphere during slab breakoff. Furthermore, rapid surface uplift during the late Early Cretaceous caused by slab breakoff made an important contribution to the formation of the proto–Tibetan Plateau. This study provides new insights into postcollisional tectonomagmatism and plateau uplift in central Tibet triggered by slab breakoff. We propose more generally that tectonic uplift during postcollisional processes (i.e., slab breakoff and lithospheric delamination) is a major contributor to plateau uplift in collision zones.

Melting modeling of mixed peridotitic and mafic lithologies at shallow depths of the continental metasomatized lithospheric mantle: Implementation for the Early Cretaceous volcanic rocks of Eastern Mongolia

The Eastern Mongolia volcanic area formed in the Late Mesozoic–Early Cenozoic within Central Asian Orogenic Belt. The main volcanic events of the area occurred in the Early Cretaceous when alkaline basaltic lavas erupted and formed the so-called cover volcanic complex. Geochemical and isotope features of the cover volcanic complex allowed researchers to identify the following mantle rocks as their source: metasomatized peridotites, eclogites, and pyroxenites. Thermodynamic modeling in alphaMELTS program was performed to determine whether the simultaneous melting of these rocks with subsequent processes of crystallization differentiation could lead to the formation of the studied rocks. The modeling results show that the melting of the most enriched with incompatible trace elements peridotites, eclogites, and pyroxenites cannot produce the rocks of the cover volcanic complex. At the same time, the mixing of peridotite- and eclogite-derived melts corresponds most closely to the mechanism of rock formation. However, Ti, K, P, Rb, and Sr enrichment of the studied rocks also requires participation in magma generation processes of mantle metasomatic veins enriched with rutile, apatite, phlogopite, and amphibole.

Zircon U-Pb ages and geochemistry of Early Cretaceous volcanic rocks, northwestern Korean Peninsula: Constraints on Late Early Cretaceous continental arc distribution in Northeast Asia

In the northwestern Korean Peninsula, Cretaceous volcanic rocks are composed of andesite, andesite-dacite and rhyolite intercalated with terrigenous clastic rocks. Zircon grains selected from these rocks are authigenic zircons with obvious crystal edges and oscillatory zoning, their Th/U ratios being generally larger than 0.4 (0.16–2.22), indicating magmatic origin. Most rocks were formed at Early Cretaceous Albian (113–103 Ma) and partially, at late Aptian, Prior to this time magmatism took place at 125 Ma and 135 Ma. All the negative εHf(t) values mean that these magma sources were contaminated by crust materials or derived from enriched mantle. Volcanic rocks belong to calc-alkaline series and partially to peraluminous series with relatively high alkali content. Chondrite-normalized REE patterns display right-lean LREE rich type and Primitive-mantle-normalized REE patterns do obvious negative anomalies in LILE (Ba, Sr), HFSE (Nb, Ta, P, Zr, Ti), but obvious positive anomalies in LIL (Rb, Pb) and HFS (Th, U, Nd). These volcanic rocks were formed in continental arc setting and their geochemical properties being similar to those of arc ADR (normal Island-Arc Andesite-Dacite-Rhyolite) suite rather than those of adakite. In the Late Early Cretaceous, west area of northeastern Asia including western Liaoning, China was in extensional setting but east area of northeastern Asia including northwestern Korean Peninsula, Jihei, eastern China and Far East areas, Russia were in continental arc setting.

Reworking of Yangtze crust into the mantle lithosphere of the North China Craton along the Dabie–East Qinling Orogen: Evidence from the Early Cretaceous volcanic rocks

Abstract Mineral chemistry, zircon U-Pb geochronology, and elemental and Sr-Nd-Pb-Hf-O isotopic data for the Early Cretaceous volcanic rocks from the Dabie and East Qinling orogens of China constrain the reworking history of the Yangtze crustal materials in the North China lithosphere. These data provide new insights into the recycling of the deepsubducted crustal materials into the mantle and the transformation process from continental subduction to collision. Our data show that the Early Cretaceous volcanic rocks are characterized by shoshonitic and high-K calc-alkaline basaltic trachyandesite, trachyandesite, and trachyte. They synchronously erupted at ca. 135–120 Ma, and have zircon in situ εHf(t) values ranging from −29.0 to −17.2, and δ18O values from 4.89‰ to 6.84‰. These samples share similar “crust-like” geochemical signatures, whole-rock enrichment in the large-ion lithophile elements, depletion in high field strength elements (Nb/La = 0.12–0.38), highly enriched Sr-Nd isotopic compositions, as well as (206Pb/204Pb)i = 15.97–17.59, (207Pb/204Pb)i = 15.33–15.54, and (208Pb/204Pb)i = 36.87–38.59. The εNd(t) values range from −24.4 to −15.6, −21.8 to −13.1, and −16.8 to −10.9 for the eastern and western North Huaiyang belts of the Dabie Orogen and the East Qinling Orogen, respectively. Such geochemical similarities suggest that the northward deep-subduction of Yangtze crustal materials have been reworked into the North China Craton enriched lithospheric mantle. The spatial pattern of the Early Cretaceous volcanic rocks suggests that the Yangtze subduction extended northward beyond the southern margin of the North China Craton and ran into its interior. The surface and deep lithospheric boundaries are decoupled between the Yangtze Block and North China Craton. The Early Cretaceous igneous rocks in the Dabie–East Qinling Orogen were induced in response to the post-collisional unrooting of the Triassic over-thickened lithosphere coupling.

Crust–mantle interaction recorded by Early Cretaceous volcanic rocks within the southern margin of the North China Craton

This study presents new geochronological and geochemical data for Early Cretaceous volcanic rocks in the southern margin of the North China Craton (NCC), to discuss the crust–mantle interaction. The studied rocks include pyroxene andesites from Daying Formation, hornblende andesites and andesites from Jiudian Formation, and rhyolites from a hitherto unnamed Formation. These rocks formed in Early Cretaceous (138–120 Ma), with enrichment in light rare earth elements (REE), depletion in heavy REE and arc-like trace elements characteristics. Pyroxene andesites show low SiO2 contents and enriched Sr–Nd–Pb–Hf isotopic compositions, with orthopyroxene phenocryst and Paleoproterozoic (2320–1829 Ma) inherited zircons, suggesting that they originated from lithospheric mantle after metasomatism with NCC lower crustal materials. Hornblende andesites have low SiO2 contents and high Mg# (Mg# = 100 Mg/(Mg + Fe2+)) values, indicating a lithospheric-mantle origin. Considering the distinct whole-rock Sr isotopic compositions we divide them into two groups. Among them, the low (87Sr/86Sr)i andesites possess amount inherited Neoarchean to Neoproterozoic (2548–845 Ma) zircons, indicating the origin of lithospheric mantle with addition of Yangtze Craton (YC) and NCC materials. In comparison, the high (87Sr/86Sr)i andesites, with abundant Neoarchean–Paleozoic inherited zircons (3499–261 Ma), are formed by partial melting of lithospheric mantle with incorporation of NCC supracrustal rocks and YC materials. Rhyolites have extremely high SiO2 (77.63–82.52 wt.%) and low total Fe2O3, Cr, Ni contents and Mg# values, combined with ancient inherited zircon ages (2316 and 2251 Ma), suggesting an origin of NCC lower continental crust. Considering the presence of resorption texture of quartz phenocryst, we propose a petrogenetic model of ‘crystal mushes’ for rhyolites prior to their eruption. These constraints record the intense crust–mantle interaction in the southern margin of the NCC. Given the regional data and spatial distribution of Early Cretaceous rocks within NCC, we believe that the formation of these rocks is related to the contemporaneous far-field effect of the Paleo-Pacific Plate.

Cretaceous Tethyan subduction in SE Borneo: Geochronological and geochemical constraints from the igneous rocks in the Meratus Complex

• The igneous rocks in the Meratus Complex mainly formed at ∼115–140 Ma. • The Cretaceous Meratus mafic rocks originated from the slab-related wedge mantle. • The Cretaceous granitoids represent the product of wedge-originated juvenile crust. • Meratus Complex has a NW-Australian affinity and formed in an fore-arc setting. • The Meratus Neotethyan Ocean subducted beneath the Argo fragment until ∼100 Ma. SE Borneo lies at the junction of the Pacific and Tethyan realms. The Mesozoic geological record of the region is dominated by convergent plate margin activity, although the geological details and its broader role in the SE Asia evolution are poorly documented. This paper presents geochronological, whole-rock elemental and Sr-Nd-Pb isotopic data on the igneous rocks from the Meratus Complex in SE Borneo. The Meratus ophiolite might form at the Late Jurassic-Early Cretaceous (∼150–115 Ma), and the spatially-associated Haruyan Volcanics, Belawayan granitoids and their equivalents generated in the Early Cretaceous (∼140–107 Ma). The Haruyan and Pitap formations and their equivalents are dominated by Early Cretaceous (∼140–115 Ma) volcanic rocks and late Early Cretaceous (∼115–100 Ma) siliciclastic rocks, respectively. The mafic-intermediate igneous rocks in the Meratus Complex are characterized by MgO = 2.04–13.20 wt%, TiO 2 = 0.48–1.51 wt%, Nb/La = 0.09–0.42, ε Nd (t) = +4.6–+7.7, ( 206 Pb/ 204 Pb) i = 18.15–18.61, ( 207 Pb/ 204 Pb) i = 15.41–15.63 and ( 208 Pb/ 204 Pb) i = 38.03–38.63, and originated from the slab-related mantle wedge. The granitoids share similar elemental ratios and Sr-Nd-Pb isotopic compositions with the coeval mafic rocks, with Nb/La = 0.20–0.30, ε Nd (t) = +4.8–+6.0, Δ8/4 = 26.2–38.8 and Δ 7/4 = 5.0–7.7, representing the products of the wedge-originated juvenile crust. Synthesis of all data reveals a NW-Australian affinity for SE Borneo. The Early Cretaceous fore-arc tectonic setting extends southerly into the Bantimala (SW Sulawesi) and Luk Ulo (Central Java), constituting a united Early Cretaceous Central Indonesian accretionary zone. The Meratus Ocean subducted beneath the Argo fragment since ∼140 Ma and likely assembled with the Sundaland margin at ∼100 Ma in response to the Neotethyan consumption.

Role of the Kerguelen mantle plume in breakup of eastern Gondwana: Evidence from early cretaceous volcanic rocks in the eastern Tethyan Himalaya

To better understand the breakup mechanism of eastern Gondwana, U Pb Zircon geochronological and whole-rock geochemical studies were performed on the Zhela and Weimei formations volcanic rocks in the Zhuode area of the eastern Tethyan Himalaya. Sensitive high-resolution ion microprobe (SHRIMP) U Pb dating of zircons yielded 206 Pb/ 238 U ages of ~135–130 Ma, indicating that the volcanic rocks from Zhela and Weimei formations erupted during the Early Cretaceous. Whole rock analyses of major and trace elements show that the volcanic rocks are characterized by high content of TiO 2 (1.84 wt%–4.03 wt%) and P 2 O 5 (0.29 wt%–0.61 wt%), highly fractioned in LREE/HREE [(La/Yb) N = 9.12–14.53], and most of them have no obvious anomaly of Eu. The characteristic, highly enriched HFSE with no obvious anomaly of Nb and Ta, is similar to those of alkali basalts originated from the Kerguelen mantle plume. Our geochemical and geochronological results, combined with recent paleomagnetic results show that the original erupted position of the Zhela and Weimei formations volcanic rocks was just located in the center of the presently Kerguelen mantle plume, and support that the Kerguelen mantle plume led to the breakup of eastern Gondwana. • The volcanic rocks from Zhela and Weimei Formation (Fm) erupted at ~130–135 Ma. • The volcanic rocks from Zhela and Weimei Fm originated from the Kerguelen plume. • The Kerguelen plume played an active role in the breakup of eastern Gondwana.

Geochronology and geochemistry of Early Cretaceous volcanic sequences in Northwestern Peru: implications for Farallon Plate subduction

ABSTRACT The Early Cretaceous geology of Northwestern (NW) Peru was characterized by emplacement of voluminous felsic volcanic rocks (e.g. the Oyotún Fm.), which have important implications for the understanding of Early Cretaceous crust-mantle interactions in the Central Andes. We present U-Pb-Hf isotopic compositions and whole-rock and trace elemental compositions of a series of Early Cretaceous volcanic rocks from the Western Cordillera and the Eastern Cordillera of the Central Andes. The volcanic rocks outcrop sporadically with limited thickness and uniform volcanic lithofacies in the western region, while the eastern region has distributions of larger scale volcanic rocks with more complex volcanic lithofacies. LA-ICP-MS zircon U-Pb dating defines the age of the Oyotún Fm. range from 138.8 Ma to 131.0 Ma in the Western Cordillera, and from 139.7 Ma to 132.3 Ma in the Eastern Cordillera. In situ Hf isotope analysis on dated zircon yield an ε Hf(t) range of +3.37 to +8.42 and a T DM2 (Hf) range from 983 Ma to 650 Ma with a peak at ca. 840 Ma. The Early Cretaceous felsic magmas are predominantly dacites and rhyolites with minor components of basalt and andesite, and show relatively homogeneous Hf isotopic compositions of zircon in single samples. Both the ε Hf(t) of zircons and the magma temperature increase from the bottom to the top of the Early Cretaceous volcanic rocks in each studied area. All these facts imply an increasing contribution of contemporaneous underplated hot and dry mantle-derived magmas with time, both as a heat source inducing crustal melting and a source of material (melt) that variably mixed with the ancient continental crustal materials.

Contrasting Sr-Nd-Pb-Hf Isotope Signatures of Early Cretaceous Volcanic Rocks from Sulu Orogenic Belt and Tanlu Fault Zone in the Southeastern North China Block: Implications for Crust-Mantle Interaction in Continental Subduction Zones

Contrasting Sr-Nd-Pb-Hf Isotope Signatures of Early Cretaceous Volcanic Rocks from Sulu Orogenic Belt and Tanlu Fault Zone in the Southeastern North China Block: Implications for Crust-Mantle Interaction in Continental Subduction Zones

Geochronology and geochemistry of Early Cretaceous bimodal volcanic rocks from Erguna Massif, NE China: evidence for the back-arc extension of the Mongol–Okhotsk orogenic belt

Geochronology and geochemistry of Early Cretaceous bimodal volcanic rocks from Erguna Massif, NE China: evidence for the back-arc extension of the Mongol–Okhotsk orogenic belt

Petrogenesis of Early Cretaceous volcanic rocks of the northeastern North China Craton: Constraints from elemental and Sr–Nd–Pb isotope geochemistry

This study examines the geochemical and whole-rock Sr–Nd–Pb isotopic compositions of Early Cretaceous volcanic rocks of the southern Jilin Province (Tonghua and Huanren areas) and Liaodong Peninsula (Xiuyan, Dandong, and Guiyunhua areas), northeastern North China Craton (NCC). Two groups of volcanic rocks are recognized in the northeastern NCC. The geochemistry and isotopic compositions of the intermediate-acid volcanic rocks indicate that a systematic decrease in whole-rock εNd(t) is accompanied by an increase of Zr/Nb. Modeling results suggest that those intermediate-acid volcanic rocks experienced the assimilation-fractional crystallization (AFC) process with different lower continental crust (LCC) components, indicating the heterogeneity of LCC in the northeastern NCC. As for basic volcanic rocks, they are characterized by “weakly enriched” isotopic signatures, i.e., moderately radiogenic Sr (0.7062–0.7082), unradiogenic Nd (−5.29 to −1.14), and highly radiogenic Pb compositions. The narrow scope of Sr–Nd–Pb isotopic compositions of whole-rock indicates insignificant crustal assimilation. Instead, the high Th/Yb ratios were largely inherited from source enrichment through the input of subducted sediment. Furthermore, element-isotopic modeling suggests that the “weakly enriched” mantle-derived rocks have resulted from a depleted mantle source metasomatized via the sediment-derived melt. Our results provide powerful petrological and geochemical evidence on the Early Cretaceous subduction of the Paleo-Pacific plate beneath the northeastern NCC and suggest the metasomatic process by subducted sediment-derived melt may play an important role in depleted mantle enrichment.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

AbstractLate Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

Early Cretaceous arc-related volcanic rocks in the northern Great Xing’an Range, NE China: records of Paleo-Pacific ocean subduction

There are widespread Late Mesozoic volcanic rocks in the Great Xing’an Range, Northeast China. However, the precise age data and tectonic evolution are still controversial. In this paper, a suite of intermediate-felsic volcanic rocks and mafic volcanic rocks have been recognized in the Daheishan of the northern Great Xing’an Range. Zircon U–Pb dating constrains two groups of the crystallization ages at 129 Ma (dacite) and 124–127 Ma (rhyolite, rhyodacite and andesite), respectively. They all have magmatic zircon geochemical characteristics, including systematic positive Ce anomalies, weak negative Eu anomalies, and high Th/U ratios (average 0.84). The intermediate-felsic volcanic rocks show crustal signatures with high K2O (1.91–7.57 wt% and low MgO (0.19–2.78 wt%) contents. The zircon eHf(t) values mostly range from + 4.7 to + 10.2, with dominant two-stage model ages (TDM2) of 530–878 Ma. Therefore, combined with previous data, the mantle-derived mafic melts may have triggered partial melting of the juvenile lower crust to produce intermediate-felsic magmas, and the source rock is considered to be an amphibolite. In addition, the trace element data of the volcanic rocks display arc-like signatures. The published and our geochronological data indicate that these Late Mesozoic volcanic rocks in the Great Xing’an Range were mainly formed in the Early Cretaceous with a peak range of 124–133 Ma. The large-scale Early Cretaceous volcanic rocks in the Great Xing’an Range were formed in an active continental margin setting related to the subduction of the Paleo-Pacific Ocean.