State Key Laboratory of Continental Dynamics

We present the first finding of continental crust-derived Precambrian zircons in garnet/spinel pyroxenite veins within mantle xenoliths carried by the Neogene Hannuoba basalt in the central zone of the North China Craton (NCC). Petrological and geochemical features indicate that these mantle-derived composite xenoliths were formed by silicic melt^lherzolite interaction. The Precambrian zircon ages can be classified into three age groups of 2·4^2·5 Ga, 1·6^2·2 Ga and 0·6^1·2 Ga, coinciding with major geological events in the NCC. These Precambrian zircons fall in the field of continental granitoid rocks in plots of U/Yb vs Hf and Y. Their igneous-type REE patterns and metamorphic zircon type CL images indicate that they were not crystallized during melt^peridotite interaction and subsequent high-pressure metamorphism.The 2·5 Ga zircons have positive eHf(t) values (2·9^10·6), whereas the younger Precambrian zircons are dominated by negative eHf(t) values, indicating an ancient continental crustal origin.These observations suggest that the Precambrian zircons were xenocrysts that survived melting of recycled continental crustal rocks and were then injected with silicate melt into the host peridotite. In addition to the Precambrian zircons, igneous zircons of 315 3 Ma (2 ), 80^170 Ma and 48^64 Ma were separated from the garnet/spinel pyroxenite veins; these provide evidence for lower continental crust and oceanic crust recycling-induced multi-episodic melt^peridotite interactions in the central zone of the NCC. The combination of the positive eHf(t) values (2·91^24·6) of the 315 Ma zircons with the rare occurrence of 302^324 Ma subduction-related diorite^granite plutons in the northern margin of the NCC implies that the 315 Ma igneous zircons might record melt^peridotite interactions in the lithospheric mantle induced by Palaeo-Asian oceanic crust subduction. Igneous zircons of age 80^170 Ma generally coexist with the Precambrian metamorphic zircons and have lower Ce/Yb and Th/U ratios, higher U/Yb ratios and greater negative Eu anomalies.The eHf(t) values of these zircons vary greatly from ^47·6 to 24·6.The 170^110 Ma zircons are generally characterized by negative eHf(t) values, whereas the 110^100 Ma zircons have positive eHf(t) values.These observations suggest that melt^peridotite interactions at 80^170 Ma were induced by partial melting of recycled continental crust. The 48^64 Ma igneous zircons are characterized by negligible Ce anomalies, unusually high REE, U and Th contents, and positive eHf(t) values.These features imply that the melt^peridotite interactions at 48^64 Ma could be associated with a depleted mantle-derived carbonate melt or fluid.

The effects of adding nitrogen to the central gas flow (Ar + He) of an Ar plasma in laser ablation inductively coupled plasma mass spectrometry are presented. The optimum central gas flow rate was found to be negatively correlated with the N2 gas flow rate. The addition of 5–10 ml min−1nitrogen to the central channel gas in LA-ICP-MS increases the sensitivity for most of the 65 investigated elements by a factor of 2–3. The degree of enhancement depends, to some extent, on the 1st ionization energy. Another important advantage of N2 mixed gas plasma for LA-ICP-MS is that the oxide ratios (ThO+/Th+) are significantly reduced (one order of magnitude). The hydride ratio (ArH+/Ar+) is also reduced up to a factor of 3, whereas the doubly charged ion ratio (Ca2+/Ca+) is increased. The background signals at masses 29, 31, 42, 51, 52 and 55 are significantly increased due to the nitrogen based polyatomic interferences. Compared to the spatial profiles of the ion distributions in the normal mode (without nitrogen), the addition of 5 ml min−1nitrogen leads to significant wider axial profiles and more uniform distribution of ions with different physical and chemical properties. Our results also show that the makeup gas flow (central channel gas) rate has a significant effect on the ion distribution of elements with different physical and chemical properties. A very consistent increase of argon signal by the addition of nitrogen (5 ml min−1) corroborates better energy transfer effect of nitrogen in the plasma.

Research Article| January 01, 2009 Contrasting Late Carboniferous and Late Permian–Middle Triassic intrusive suites from the northern margin of the North China craton: Geochronology, petrogenesis, and tectonic implications Shuan-Hong Zhang; Shuan-Hong Zhang † 1Key Laboratory of Crustal Deformation and Processes, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China, and Beijing SHRIMP Center, Chinese Academy of Geological Sciences, Beijing 100037, China †E-mail: tozhangshuanhong@163.com. Search for other works by this author on: GSW Google Scholar Yue Zhao; Yue Zhao 2Key Laboratory of Crustal Deformation and Processes, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Biao Song; Biao Song 3Beijing SHRIMP Center, Chinese Academy of Geological Sciences, Beijing 100037, China Search for other works by this author on: GSW Google Scholar Jian-Min Hu; Jian-Min Hu 4Key Laboratory of Crustal Deformation and Processes, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Shu-Wen Liu; Shu-Wen Liu 5Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China Search for other works by this author on: GSW Google Scholar Yue-Heng Yang; Yue-Heng Yang 6State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Fu-Kun Chen; Fu-Kun Chen 6State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Xiao-Ming Liu; Xiao-Ming Liu 7State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China Search for other works by this author on: GSW Google Scholar Jian Liu Jian Liu 8Key Laboratory of Crustal Deformation and Processes, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2009) 121 (1-2): 181–200. https://doi.org/10.1130/B26157.1 Article history received: 24 Nov 2006 rev-recd: 12 Oct 2007 accepted: 13 Nov 2007 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Shuan-Hong Zhang, Yue Zhao, Biao Song, Jian-Min Hu, Shu-Wen Liu, Yue-Heng Yang, Fu-Kun Chen, Xiao-Ming Liu, Jian Liu; Contrasting Late Carboniferous and Late Permian–Middle Triassic intrusive suites from the northern margin of the North China craton: Geochronology, petrogenesis, and tectonic implications. GSA Bulletin 2009;; 121 (1-2): 181–200. doi: https://doi.org/10.1130/B26157.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Two contrasting intrusive suites have been identified from the northern margin of the North China craton: a Late Carboniferous dioritegranodiorite suite mainly made up of quartz diorite, diorite, granodiorite, tonalite, and hornblende gabbro, and a Late Permian–Middle Triassic suite of granitoid intrusions consisting of monzogranite, syenogranite, and quartz monzonite. Plutons from the Late Carboniferous suite exhibit variable SiO2 contents and calc-alkaline or high-K calc-alkaline, metaluminous geochemical features. Most have low negative whole-rock ϵNd(T) values (where T is the crystallization age) of −17.1 to −11.5 and zircon ϵHf(T) values of −38.3 to −11.2, indicating that they were derived mainly from anatectic melting of the ancient lower crust with some involvement of mantle materials. However, an older pluton in the suite exhibits higher ϵNd(T) values of −11.5 to −9.9, Nd model ages of 1.82–1.64 Ga, lower initial 87Sr/86Sr ratios of 0.7046–0.7048, and it contains some zircon grains that are characterized by high negative to positive zircon ϵHf(T) values of −8.7 to 1.2, indicating strong involvement of juvenile materials derived from the lithospheric mantle. The Late Carboniferous plutons are interpreted as subduction-related and to have been emplaced in an Andean-style continental-margin arc during the southward subduction of the paleo–Asian oceanic plate beneath the North China craton. Rocks from the Late Permian–Middle Triassic intrusive suite display geochemical signatures ranging from highly fractionated I-type to A-type. They exhibit higher zircon ϵHf(T) values of −14.9 to −6.7, whole-rock ϵNd(T) values of −10.6 to −8.8, and younger Hf and Nd model ages than most of the Late Carboniferous plutons, indicating that they could have been produced by extreme fractional crystallization of hybrid magmas resulted from mixing of coeval mantle- and crust-derived melts. They are interpreted as postcollisional/postorogenic granitoids linked to lithospheric extension and asthenosphere upwelling due to slab break-off and subsequent sinking after final collision and suturing of the Mongolian arc terranes with the North China craton. These two contrasting intrusive suites suggest that the final closure of the paleo–Asian Ocean and collision between the Mongolian arc terranes and the North China craton occurred during the Late Permian, and these events were followed by postcollisional/postorogenic extension, large-volume magmatism, and significant continental growth. No significant syncollisional crustal thickening, high-pressure metamorphism, or S-type granitoid magmatism occurred during the collision process. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Clastic sedimentary rocks are natural samples of the exposed continental crust over large areas. The age and evolution of the Yangtze craton is not well known, because much of the craton is covered by thick Nanhua (850 --635Ma), Sinian (635 --543Ma) and Phanerozoic sedimentary rocks. The Nanhua clastic sedimentary rocks including tillites provide ideal samples for studies of age and evolution of the craton. 1130 zircons in 8 sandstone and tillite samples of three Nanhua formations (Liantuo, Gucheng and Nantuo) from the Yangtze Gorges area were dated by LA-ICP-MS. 251 of the 711 concordant zircons were analyzed for Hf isotopic compositions by LA-MC-ICP-MS. The results reveal four major age groups of 720 to 910 Ma, 1.90 to 2.05 Ga, 2.40 to 2.55Ga and 2.60 to 2.70 Ga with few grains \>3.2Ga. Although Hf isotopic compositions show both juvenile crustal growth and reworking of old crust for all the age groups, the Paleoproterozoic is a period of prominent crustal reworking with negative ε~Hf~(t) values. The Neoproterozoic is a period of significant juvenile crustal additions, accounting for 68 percent of zircons with positive ε~Hf~(t) values similar to those of the depleted mantle. Crustal additions at 3.2 to 3.8Ga are also significant, as indicated by the zircon Hf continental model ages. Our results highlight the importance of analysis of a sufficient number of zircons for provenance studies. In addition, our results illustrate that possible temporal and spatial provenance variations have to be taken into account for better characterizing formation and evolution of the related continental crust. Our obtained youngest age for each formation shows a strong negative correlation with stratigraphic height. Youngest ages provide good constraints on the maximum ages of the three Nanhua formations: ≤770Ma, ≤733Ma and ≤704Ma for the base, middle unit and top of the Liantuo Formation, respectively; ≤703Ma for the Gucheng Formation and possibly ≤600 to 606Ma for the Nantuo Formation. Although the North China and Yangtze cratons show some apparently similar zircon ages, the two cratons have distinct histories of formation and evolution. While the North China craton is dominated by Archean crustal growth, the Yangtze craton is characterized by prominent crustal additions in the Neoproterozoic, which is almost lacking in the North China craton.

Abstract We present an updated oceanic crustal age grid and a set of complementary grids including spreading rate, asymmetry, direction, and obliquity. Our data set is based on a selected set of magnetic anomaly identifications and the plate tectonic model of Müller et al. (2019, 10.1029/2018TC005462 ). We find the mean age of oceanic crust is 64.2 Myr, slightly older than previous estimates, mainly due to the inclusion of pockets of Mesozoic aged crust in the Atlantic and Mediterranean and improvements to the Jurassic Pacific triangle. This older crust is partly compensated by additional Cenozoic‐aged back‐arc basin crust not included in previous models. The distribution of spreading modes based on area of preserved crust is relatively equal between slow (20–55 mm/yr) and fast (75–180 mm/yr) spreading systems at 33% and 39%, respectively. Crust transitional between fast and slow, or intermediate systems (55–75 mm/yr), cover 20% of the preserved ocean floor with much smaller proportions of crust formed at ultraslow (5%) and super‐fast (3%) spreading systems. Slow and intermediate spreading systems exhibit the most stable behavior in terms of spreading asymmetry and obliquity, with the widest distribution of obliquities occurring at ultraslow spreading systems, consistent with present‐day observations. Our confidence grid provides a complementary resource for nonexperts to identify those parts of the age grid that are least well constrained. Our grids in 6, 2, and 1 arc min resolution as well as our python workflow, isopolate , used to compute our data sets are freely available in online repositories and on the GPlates data portal.

• Analysis of brGDGT distributions in global peat dataset. • Correlation of brGDGT distributions with peat pH and mean annual air temperature. • Development of peat-specific temperature and pH proxies. Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (−8 to 27 °C) and pH (3–8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 × CBT peat + 8.07 ( n = 51, R 2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAAT peat (°C) = 52.18 × MBT 5me ′ − 23.05 ( n = 96, R 2 = 0.76, RMSE = 4.7 °C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (∼4.7 °C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (∼15.2 kyr), we demonstrate that MAAT peat yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAAT peat to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate.

Parasite-host systems are pervasive in nature but are extremely difficult to convincingly identify in the fossil record. Here we report quantitative evidence of parasitism in the form of a unique, enduring life association between tube-dwelling organisms encrusted to densely clustered shells of a monospecific organophosphatic brachiopod assemblage from the lower Cambrian (Stage 4) of South China. Brachiopods with encrusting tubes have decreased biomass (indicating reduced fitness) compared to individuals without tubes. The encrusting tubes orient tightly in vectors matching the laminar feeding currents of the host, suggesting kleptoparasitism. With no convincing parasite-host interactions known from the Ediacaran, this widespread sessile association reveals intimate parasite-host animal systems arose in early Cambrian benthic communities and their emergence may have played a key role in driving the evolutionary and ecological innovations associated with the Cambrian radiation.

Abstract Migmatite gneisses are widespread in the Dabie orogen, but their formation ages are poorly constrained. Eight samples of migmatite, including leucosome, melanosome, and banded gneiss, were selected for U–Pb dating and Hf isotope analysis. Most metamorphic zircon occurs as overgrowths around inherited igneous cores or as newly grown grains. Morphological and internal structure features suggest that their growth is associated with partial melting. According to the Hf isotope ratio relationships between metamorphic zircon and inherited cores, three formation mechanisms for metamorphic zircon can be determined, which are dissolution–reprecipitation of pre‐existing zircon, breakdown of Zr‐bearing phase other than zircon in a closed system and crystallization from externally derived Zr‐bearing melt. Four samples contain magmatic zircon cores, yielding upper intercept U–Pb ages of 807 ± 35–768 ± 12 Ma suggesting that the protoliths of the migmatites are Neoproterozoic in age. The migmatite zircon yields weighted mean two‐stage Hf model ages of 2513 ± 97–894 ± 54 Ma, indicating reworking of both juvenile and ancient crustal materials at the time of their protolith formation. The metamorphic zircons give U–Pb ages of 145 ± 2–120 ± 2 Ma. The oldest age indicates that partial melting commenced prior to 145 Ma, which also constrains the onset of extensional tectonism in this region to pre‐145 Ma. The youngest age of 120 Ma was obtained from an undeformed granitic vein, indicating that deformation in this area was complete at this time. Two major episodes of partial melting were dated at 139 ± 1 and 123 ± 1Ma. The first episode of partial melting is obviously older than the timing of post‐collision magmatism, corresponding to regional extension. The second episode of partial melting is coeval with the widespread post‐collision magmatism, indicating the gravitational collapse and delamination of the orogenic lithospheric keel of the Dabie orogen, which were possibly triggered by the uprising of the Cretaceous mid‐Pacific superplume.

We present new geochronological and geochemical data for granites and volcanic rocks of the Erguna massif, NE China. These data are integrated with previous findings to better constrain the nature of the massif basement and to provide new insights into the subduction history of Mongol–Okhotsk oceanic crust and its closure. U–Pb dating of zircons from 12 granites previously mapped as Palaeoproterozoic and from three granites reported as Neoproterozoic yield exclusively Phanerozoic ages. These new ages, together with recently reported isotopic dates for the metamorphic and igneous basement rocks, as well as Nd–Hf crustal-residence ages, suggest that it is unlikely that pre-Mesoproterozoic basement exists in the Erguna massif. The geochronological and geochemical results are consistent with a three-stage subduction history of Mongol–Okhotsk oceanic crust beneath the Erguna massif, as follows. (1) The Erguna massif records a transition from Late Devonian A-type magmatism to Carboniferous adakitic magmatism. This indicates that southward subduction of the Mongol–Okhotsk oceanic crust along the northern margin of the Erguna massif began in the Carboniferous. (2) Late Permian–Middle Triassic granitoids in the Erguna massif are distributed along the Mongol–Okhotsk suture zone and coeval magmatic rocks in the Xing’an terrane are scarce, suggesting that they are unlikely to have formed in association with the collision between the North China Craton and the Jiamusi–Mongolia block along the Solonker–Xra Moron–Changchun–Yanji suture zone. Instead, the apparent subduction-related signature of the granites and their proximity to the Mongol–Okhotsk suture zone suggest that they are related to southward subduction of Mongol–Okhotsk oceanic crust. (3) A conspicuous lack of magmatic activity during the Middle Jurassic marks an abrupt shift in magmatic style from Late Triassic–Early Jurassic normal and adakite-like calc-alkaline magmatism (pre-quiescent episode) to Late Jurassic–Early Cretaceous A-type felsic magmatism (post-quiescent episode). Evidently a significant change in geodynamic processes took place during the Middle Jurassic. Late Triassic–Early Jurassic subduction-related signatures and adakitic affinities confirm the existence of subduction during this time. Late Jurassic–Early Cretaceous post-collision magmatism constrains the timing of the final closure of the Mongol–Okhotsk Ocean involving collision between the Jiamusi–Mongolia block and the Siberian Craton to the Middle Jurassic.

Abstract U–Pb age, trace element and Hf isotope compositions of zircon were analysed for a metasedimentary rock and two amphibolites from the Kongling terrane in the northern part of the Yangtze Craton. The zircon shows distinct morphological and chemical characteristics. Most zircon in an amphibolite shows oscillatory zoning, high Th/U and 176 Lu/ 177 Hf ratios, high formation temperature, high trace element contents, clear negative Eu anomaly, as well as HREE‐enriched patterns, suggesting that it is igneous. The zircon yields a weighted mean 207 Pb/ 206 Pb age of 2857 ± 8 Ma, representing the age of the magmatic protolith. The zircon in the other two samples is metamorphic. It has low Th/U ratios, low trace element concentrations, variable HREE contents (33.8 ≥ Lu N ≥2213; 14.7 ≤ Lu N /Sm N ≤ 354) and 176 Lu/ 177 Hf ratios (0.000030–0.001168). The data indicate that the zircon formed in the presence of garnet and under upper amphibolite facies conditions. The metamorphic zircon yields a weighted mean 207 Pb/ 206 Pb age of 2010 ± 13 Ma. These results combined with previously obtained Palaeoproterozoic metamorphic ages suggest a c. 2.0 Ga Palaeoproterozoic collisional event in the Yangtze Craton, which may result from the assembly of the supercontinent Columbia. The zircon in two samples yields weighted mean two‐stage Hf model ( T DM2 ) ages of 3217 ± 110 and 2943 ± 50 Ma, respectively, indicating that their protoliths were mainly derived from Archean crust.

Abstract Quartz veins in high‐pressure to ultrahigh‐pressure metamorphic rocks witness channelized fluid flow that transports both mass and heat during collisional orogenesis. This flow can occur in the direction of changing temperature/pressure during subduction or exhumation. SHRIMP U‐Pb dating of zircon from a kyanite‐quartz vein within ultrahigh‐pressure eclogite in the Dabie continental collision orogen yields two age groups at 212 ± 7 and 181 ± 13 Ma, which are similar to two groups of LA‐ICPMS age at 210 ± 4 and 180 ± 5 Ma for the same sample. These ages are significantly younger than zircon U‐Pb ages of 224 ± 2 Ma from the host eclogite. Thus the two age groups from the vein date two episodes of fluid flow involving zircon growth: the first due to decompression dehydration during exhumation, and the second due to heating dehydration in response to a cryptic thermal event after continental collision. Laser fluorination O‐isotope analyses gave similar δ 18 O values for minerals from both vein and eclogite, indicating that the vein‐forming fluid was internally derived. Synchronous cooling between the vein and eclogite is suggested by almost the same quartz–mineral fractionation values, with regularly decreasing temperatures that are in concordance with rates of O diffusion in the minerals. While the quartz veining was caused by decompression dehydration at 700–650 °C in a transition from ultrahigh‐pressure to high‐pressure eclogite‐facies retrogression, the postcollisional fluid flow was retriggered by heating dehydration at ∼500 °C without corresponding metamorphism. In either case, the kyanite–quartz vein formed later than the peak ultrahigh‐pressure metamorphic event at the Middle Triassic, pointing to focused fluid flow during exhumation rather than subduction. The growth of metamorphic zircon in the eclogite appears to have depended on fluid availability, so that their occurrence is a type of geohygrometer besides geochronological applicability to dating of metamorphic events in orogenic cycles.

Ordos basin has developed during middle—late Triassic and early Cretaceous and has been reformed since late Cretaceous. It mainly possesses the characters of intra-craton and is a residual basin with multi-stage and different reformation. Ordos basin also belongs to multi-superimposed basin which overlapped on the early and late Paleozoic basins. Therefore, Multi-energy mineral deposits are abundant and petroleum, coal and uranium are beared in the same basin. According to the the main geological structure features and geological events in ordos baisn and peripheral areas, together with the comprehensional research of the fission track ages in various district of the basin, the paper concludes that there exists four evident stages of structural fluctuation at least during basin development and also four stages of evolution and sedimentation in the basin. middle—late Triassic and early—middle Jurassic Fuxian and Yan'an stage is the two most prosperous stages during which the lake is broad and basin deposits extensively with an area over two times of that of present, the main oil and coal bearing strata develop. The two stages are divided by the regional early Jurassic uplift fluctuation, which causes interruption in deposition and development of the roughness of relief on the upper part of the Yanchang formation by reason of forceful and uneven cutting erosion. The uplift fluctuation is weak and the depositional interruption and erosion continuous time is short at the evening of Yan'an stage. Then basin subsides and enters the third evolution stage of middle Jurassic Zhiluo—Anding stage in which sedimentary range is still broad and the lake area is minish in the basin. There happens strongly structural movement and developed the thrust-nappe belt in western margin of the basin in late Jurassic during which the different depth of conglomerate deposit in the foredeep part in the east side of the western margin, erosion reform occurs in the middle and east of the basin. The structural movement causes the form of structure framework of regional east uplift and west subside in the west area of Yellow river. Broad sediments unconformablely overlap on the west margin thrust belt and sideral uplift of the basin north and south at the early Cretaceous stage. Ordos basin uplifts wholly to disappear and enters the late reformation period. In the first three stages, the depocenters lie near or to the east of Yan'an city, while deposit center in the west of the basin near provenance. The two centers differs in space in different stage. Until early Cretacious, the location of sedimentary depocenters and accumulation center is nearly same which is on the middle-south part of the west of the basin. There happen six major geological events in Ordos basin in late reformation period since late Cretaceous. (1) The main part of the basin uplifts continuously, episodically and differently, which causes the strong and uneven erosion, for example, the max erosion depth in Mesozoic can be two thousand meters near Yellow river on the east. (2) This uplift forms two or three stages of regional erosion-planation surfaces with ages of E 3-1__2,E_3 and N2_1. (3) The side of Ordos block subsides and the peripheral faulted basins form successively to deposit with heavy depth. (4) The regional east uplift and west subside movement continuing two bill years has been reversed which means the east subsides to widely deposit red clay and Liupianhshan, western margin of Ordos block and west part of basin uplift successively. The reverse event embodies the important influence of the regional structural movement of the west of China. (5) Aeolian red clay and loess begin to sediment broadly in 8Ma BPand 2.5Ma BP, respectively. Also the red mud semi-plateau, loess plateau and loess plateau surface develop successively. (6) Drainage system of Yellow river grows and fluid outside to erode the side rock. According to the above major geological events and the evolution of dynamics environment, five evolution stages is divided since late Cretaceous in Ordos basin which are late Cretaceous to Paleocene, Eocene to Oligocene, early—middle Miocene, late Miocene to Pliocene and Quaternary. The happening of these geological events and structural fluctuation are closely related with the compound, superimpose, change with time and strong-weak of major structural movement of peripheral structural domain especially that of the east and west of China. These activity and reformation change the Mesozoic prototype basin topography greatly.The main times and stages of the occurrence and formation and reset of miltiple energy resources have evident recall and decoupling relations with those of the Mesozoic and Cenozoic evolution and reformation in Ordos basin. The whole different uplift and regional erosion in and after the late of basin evolution own the important influence to the formation and distribution of the milti-mineral deposits and the coaction among them in Ordos basin.

Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preserved in sandstones and siltstones. Here we report several iconic Ediacara fossils and an annulated tubular fossil (reconstructed as an erect epibenthic organism with uniserial arranged modular units), from marine limestone of the 551-541 Ma Dengying Formation in South China. These fossils significantly expand the ecological ranges of several key Ediacara taxa and support that they are marine organisms rather than terrestrial lichens or microbial colonies. Their close association with abundant bilaterian burrows also indicates that they could tolerate and may have survived moderate levels of bioturbation.

We show the way to synthesize chalcopyrite glass for <italic>in situ</italic> sulfur isotope measurements using fsLA-MC-ICP-MS.

The amalgamation of South (SCB) and North China Blocks (NCB) along the Qinling-Dabie orogenic belt involved several stages of high pressure (HP)-ultra high pressure (UHP) metamorphism. The new discovery of UHP metamorphic rocks in the North Qinling (NQ) terrane can provide valuable information on this process. However, no precise age for the UHP metamorphism in the NQ terrane has been documented yet, and thus hinders deciphering of the evolution of the whole Qinling-Dabie-Sulu orogenic belt. This article reports an integrated study of U–Pb age, trace element, mineral inclusion and Hf isotope composition of zircon from an eclogite, a quartz vein and a schist in the NQ terrane. The zircon cores in the eclogite are characterized by oscillatory zoning or weak zoning, high Th/U and 176Lu/177Hf ratios, pronounced Eu anomalies and steep heavy rare earth element (HREE) patterns. The zircon cores yield an age of 796 ± 13 Ma, which is taken as the protolith formation age of the eclogite, and implies that the NQ terrane may belong to the SCB before it collided with the NCB. The ɛHf(t) values vary from −11.3 to 3.2 and corresponding two-stage Hf model ages are 2402 to 1495 Ma, suggesting the protolith was derived from an enriched mantle. In contrast, the metamorphic zircon rims show no zoning or weak zoning, very low Th/U and 176Lu/177Hf ratios, insignificant Eu anomalies and flat HREE patterns. They contain inclusions of garnet, omphacite and phengite, suggesting that the metamorphic zircon formed under eclogite facies metamorphic conditions, and their weighted mean 206Pb/238U age of 485.9 ± 3.8 Ma was interpreted to date the timing of the eclogite facies metamorphism. Zircon in the quartz vein is characterized by perfect euhedral habit, some oscillatory zoning, low Th/U ratios and variable HREE contents. It yields a weighted mean U–Pb age of 480.5 ± 2.5 Ma, which registers the age of fluid activity during exhumation. Zircon in the schist is mostly detrital and U–Pb age peaks at c. 1950 to 1850, 1800 to 1600, 1560 to 1460 and 1400 to 1260 Ma with an oldest grain of 2517 Ma, also suggesting that the NQ terrane may have an affinity to the SCB. Accordingly, the amalgamation between the SCB and the NCB is a multistage process that spans c. 300 Myr, which includes: the formation of the Erlangping intra-oceanic arc zone onto the NCB before c. 490 Ma, the c. 485 Ma crustal subduction and UHP metamorphism of the NQ terrane, the c. 430 Ma arc-continent collision and granulite facies metamorphism, the 420 to 400 Ma extension and rifting in relation to the opening of the Palaeo-Tethyan ocean, the c. 310 Ma HP eclogite facies metamorphism of oceanic crust and associated continental basement, and the final 250 to 220 Ma continental subduction and HP–UHP metamorphism.

The greatest strength of the LA-ICP-MS technique is its application to microsampling in which extremely small pits are obtained. The results of this study highlight some significant different laser-induced fractionations between widely used external reference materials NIST SRM 610–614 and natural silicate reference materials (e.g., USGS reference glasses (GSE-1G, GSD-1G), MPI-DING glasses, USGS basalt glasses and zircon reference material GJ-1) at high spatial resolution analysis. For the sample matrices and analytical conditions used in this study, the laser-induced elemental fractionations for 63 selected isotopes are negligible at the spot sizes of 160–44 µm. However, the laser-induced elemental fractionations of Li, Na, Si, K, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Cs and U (with respect to Ca) increase significantly with decreasing spot sizes from 44 µm to 32 µm, 24 µm and 16 µm in these natural silicate reference materials. Unlike in these sample matrices, laser-induced elemental fractionations of these elements in NIST SRM 610–614 are unique in that they are almost not affected by the change of spot sizes from 44 to 32 to 24 µm, with only slight increase at the spot sizes of 16 µm. The much less significant laser-induced elemental fractionation in NIST SRM 61X in comparison with other natural silicate materials makes them not ideal as external reference materials at high spatial resolution analysis. Alternatively, this NIST SRM 61X-specific matrix effect for Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Cs and U can be minimized by using Si for internal standardization. U and Pb in zircon GJ-1 are exceptions, which are zircon-specific.

Kuangping Group located in North Qinling orogenic belt which consists chiefly of metabasalts and meta-sedimentary.A new LA-ICPMS zircon U-Pb age of metabasalt of Kuanping Group is presented and gives a weighted mean 207Pb/206Pb age of 943Ma which in the Neo-proterozoic time.However,the meta-sedimentary of Kuanping Group is limited to that in Early Phanerozoic time,but the Proterozoic,as previously considered.Therefore,this indicate that the two types of rock is not a continuous stratigraphic unit,protoliths of metabasalts were tholeiitic basalts with N-MORB geochemical characteristics,which represents a dismembered ophiolite and indicate a remnants of Greenville orogeny in the North Qinling orogenic belts.

Abstract In the Cretaceous, the subduction of the Izanagi/Paleo‐Pacific plates beneath the South China Block (SCB) created a wide back‐arc domain characterized by numerous extensional basins coeval with voluminous magmatism. The SCB witnessed the whole evolution by records of widespread extensional structures to accommodate the lithospheric stretching. In the interior of the SCB, the Yuechengling (YCL) Massif preserves a large, low‐angle detachment fault, the Ziyuan Detachment (ZYD) at the western margin, and a high‐angle ductile normal fault, the Tianhu Fault (THF), in the middle of the massif. Both faults display ductile shearing with top‐to‐the west kinematics but play different roles in two stages of extension. In the early stage at 140–120 Ma, the THF deformed the eastern YCL pluton at a temperature of ~350 °C, but the ZYD shows limited movement at this time. On the contrary, the later stage (100–85 Ma) is characterized by pervasive middle‐ to high‐temperature deformation (~400–500 °C) and rapid exhumation along the ZYD, but the THF only underwent a near‐surface brittle overprint. Across the SCB, the two‐phase extension is widely recorded in other extensional structures and coincides with magmatic flare‐ups at its eastern margin, suggesting episodic changes in the subduction dip. Combined with two compressional events that took place between the intervals of extension, the SCB experienced two cycles of compression‐extension at 155–120 and 120–85 Ma. This periodicity is tentatively interpreted as a combined effect from the Izanagi/Paleo‐Pacific subduction angle change and a thickening‐foundering process in the arc region.

Abstract The continental crust is unique to the Earth in the solar system, and controversies remain regarding its origin, accretion and reworking of continents. The plate tectonics theory has been significantly challenged in explaining the origin of Archean (especially pre‐3.0 Ga) continents as they rarely preserve hallmarks of plate tectonics. In contrast, growing evidence emerges to support oceanic plateau models that better explain characteristics of Archean continents, including the bimodal volcanics and nearly coeval emplacement of tonalite‐trondjhemite‐granodiorite (TTG) rocks, presence of ∼1600°C komatiites and dominant dome structures, and lack of ultra‐high‐pressure rocks, paired metamorphic belts and ophiolites. On the other hand, the theory of plate tectonics has been successfully applied to interpret the accretion of continents along subduction zones since the late Archean (3.0–2.5 Ga). During subduction processes, the new mafic crust is generated at the base of continents through partial melting of mantle wedge with the addition of H 2 O‐dominant fluids from subducted oceanic slabs and partial melting of the juvenile mafic crust results in the generation of new felsic crusts. This eventually leads to the outgrowth of continents. Subduction processes also cause softening, thinning, and recycling of continental lithosphere due to the vigorous infiltration of volatile‐rich fluids and melts, especially along weak belts/layers, leading to widespread continental reworking and even craton destruction. Reworking of continents also occurs in continental interiors due to either plate boundary processes or plume‐lithosphere interactions. The effects of plumes have proven to be less significant and cause lower degrees of lithospheric modification than subduction‐induced craton destruction.

Abstract Combining 121 new fission track and (U‐Th)/He ages with published thermochronologic data, we investigate the Late Cretaceous‐Cenozoic exhumation/cooling history of the eastern Tibetan Plateau, Qinling, Daba Shan, and Sichuan Basin of east central China. The Qinling orogen shows terminal southwestward foreland growth in the northern Daba Shan thrust belt at 100–90 Ma and in the southern Daba Shan fold belt at 85–70 Ma. The eastern margin of Tibetan Plateau experienced major exhumation phases at 70–40 Ma (exhumation rate 0.05–0.08 mm/yr), 25–15 Ma (≤1 mm/yr in the Pengguan Massif; ~0.2 mm/yr in the imbricated western Sichuan Basin), and since ~11–10 Ma along the Longmen Shan (~0.80 mm/yr) and the interior of the eastern Tibetan Plateau (Dadu River gorge, Min Shan; ~0.50 mm/yr). The Sichuan Basin records two basin‐wide denudation phases, likely a result of the reorganization of the upper Yangtze River drainage system. The first phase commenced at ~45 Ma and probably ended before the Miocene; &gt;1 km of rocks were eroded from the central and eastern Sichuan Basin. The second phase commenced at ~12 Ma and denudated the central Sichuan Basin, Longmen Shan, and southern Daba Shan; more than 2 km of rocks were eroded after the lower Yangtze River had cut through the Three Gorges and captured the Sichuan Basin drainage. In contrast to the East Qinling, which was weakly effected by late Cenozoic exhumation, the West Qinling and Daba Shan have experienced rapid exhumation/cooling since ~15–13 Ma, a result of growth of the Tibetan Plateau beyond the Sichuan Basin.