Magmatic evolution of the southern Coast Belt: constraints from Nd–Sr isotopic systematics and geochronology of the southern Coast Plutonic Complex

1995 ◽  
Vol 32 (10) ◽  
pp. 1681-1698 ◽  
Author(s):  
R. M. Friedman ◽  
J. B. Mahoney ◽  
Y. Cui
Keyword(s):  
Middle Jurassic ◽  
Igneous Rocks ◽  
Geochemical Data ◽  
Crustal Rock ◽  
Southern Coast ◽  
Magmatic Arc ◽  
Field Evidence ◽  
Depleted Mantle ◽  
Zircon Crystallization ◽  
Wide Range

Igneous rocks of the southern Coast Belt (SCB) and adjacent Insular Belt developed within a Jurassic–Quaternary magmatic arc built across accreted juvenile-arc and oceanic terranes. SCB plutons are mostly of intermediate composition, with I-type characteristics and major element, trace element, and rare earth element geochemistry consistent with genesis in a subduction-related magmatic arc. Ubiquitous xenoliths and migmatitic zones at pluton–county rock contacts indicate that assimilation of crustal rock was an important magmatic process. U–Pb zircon crystallization ages for SCB and Insular Belt igneous rocks indicate an overall eastward migration of the magmatic axis from Middle Jurassic through Late Cretaceous time. Although absent in most rocks, traces of old inherited zircon are present in several Middle Jurassic–Upper Cretaceous plutons in the southeastern Coast Belt. The primitive character and restricted range of Nd–Sr isotopic data for Middle Jurassic to Quaternary igneous rocks of the SCB (εNd = +2.4 to +8.0; Sri = 0.7030 − 0.7042) indicate they were generated in an isotopically juvenile magmatic arc. The distribution of isotopic values along the mantle array and the wide range of fSm/Nd values suggest magma was derived from depleted mantle within a mantle wedge, with little or no contribution from old, isotopically evolved continental material. Although field evidence suggests that assimilation of juvenile crust was an important process during magma ascent, isotopic and geochemical data do not permit discrimination between direct mantle derivation of magmas followed by fractionation and crustal assimilation, and wholesale melting of mafic arc-derived lower crust.

Reappraisal of the Mesozoic tectonic transition from the Paleo-Tethyan to Paleo-Pacific domains in South China

2021 ◽  
Author(s):  
Chengshi Gan ◽  
Yuzhi Zhang ◽  
Yuejun Wang ◽  
Xin Qian ◽  
Yang Wang
Keyword(s):  
South China ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Sedimentary Rocks ◽  
Early Jurassic ◽  
Igneous Rocks ◽  
Late Triassic ◽  
Geochemical Data ◽  
South China Block ◽  
Tectonic Transition

The southeastern (SE) South China Block was mainly influenced by the Paleo-Tethyan and Paleo-Pacific dynamic domains during the Mesozoic. The initial timing of the tectonic transition between these two domains in the SE South China Block still remains debated. The transition would affect the nature of the lithosphere and material provenance of sediments, and, therefore, igneous and sedimentary rocks in the area could record such dynamic processes. In this study, published geochronological and geochemical data of the Triassic and Jurassic igneous rocks and detrital zircon data of contemporaneous sedimentary rocks in the SE South China Block were compiled, aiming to provide constraints on the tectonic transition via tracing the spatial-temporal variations in the nature of the lithosphere and sedimentary provenance signals. The compiled results suggest that the magmatic intensity and volume decreased significantly from the Late Triassic to Early−Middle Jurassic, with an obvious magmatic quiescence between them, and increased from the Early−Middle Jurassic to Late Jurassic. The εNd(t) and zircon εHf(t) values of mafic rocks, granitoids, and shoshonitic rocks remarkably increased from the Late Triassic to Early−Middle Jurassic, indicative of variations in the lithospheric mantle and continental crust. Such variations suggest that the initial tectonic transition occurred at the earliest Early Jurassic. Based on the southward paleocurrents from Early Jurassic sandstone, E-W−trending extension of Early−Middle Jurassic mafic and shoshonitic rocks, and similar sedimentary provenances of Late Triassic and Early−Middle Jurassic sedimentary rocks, these features imply that the SE South China Block was not immediately influenced by the Paleo-Pacific domain during the Early−Middle Jurassic. However, from the Early−Middle Jurassic to Late Jurassic and Early Cretaceous, the spatial distribution, geochemical signatures, magmatic intensity, and magmatic volume of igneous rocks and provenance of sedimentary rocks exhibit obvious variations, and the regional fold hinge direction changed from E-W−trending to NE-trending, suggesting significant effects from Paleo-Pacific subduction on the SE South China Block. Thus, the Mesozoic tectonic transition from the Paleo-Tethyan to the Paleo-Pacific dynamic domain in the SE South China Block likely occurred during the Early−Middle Jurassic.

Early Permian subduction-related transtension in the Turpan Basin, East Tianshan (NW China): implications for accretionary tectonics of the southern Altaids

2019 ◽  
Vol 158 (1) ◽  
pp. 175-198 ◽  
Author(s):  
Qigui Mao ◽  
Wenjiao Xiao ◽  
Brian F. Windley ◽  
Minjie Yu ◽  
Min Sun ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Early Permian ◽  
Spatial Features ◽  
Depleted Mantle ◽  
Zircon Crystallization ◽  
Type Granite ◽  
Ocean Ridge ◽  
East Tianshan

AbstractThe interaction of the Palaeo-Pacific and Palaeo-Asian Oceans is an enigmatic issue as their temporal and spatial features are controversial. To address this issue, we present a systematic study of large volumes of early Permian volcanic rocks and intrusions developed in the East Tianshan. The represented samples of basaltic andesites and rhyolites yield zircon crystallization ages of 285.1 ± 5.9 Ma and 275.3 ± 1.8 Ma, respectively. The basalts have normal mid-ocean ridge basalt (N-MORB) and arc-related geochemical signatures with high TiO2 contents, negative Rb, Th, U, Nb and Ta anomalies and positive Eu anomalies. Basaltic andesites and andesites have arc-related geochemical characteristics with moderate TiO2 contents and relatively negative Nb, Ta and Ti anomalies, together with slightly negative to positive Eu anomalies. The rhyolites show an affinity with A2-type granite with high SiO2, K2O + Na2O, Fe/Mg, Ga, Zr, Nb, Y, HFSE, REE and Y/Nb levels (>1.2). These geochemical data suggest that the rocks formed in a supra-subduction zone. The presence of high ϵNd(t) values of +4.6 to +8.2 and low (87Sr/86Sr)i (0.70342–0.70591) values indicates that the volcanic rocks originated from a depleted mantle. We propose that oblique subduction with slabs breaking off gave rise to transtension and to the emplacement of large volumes of mantle-derived melts in the early Permian in the East Tianshan, serving as an important record of the subduction zone of the Palaeo-Pacific Ocean.

Continental tholeiitic mafic rocks of the Paleoproterozoic Hurwitz Group, Central Hearne sub-domain, Nunavut: insight into the evolution of the Hearne sub-continental lithosphere

2003 ◽  
Vol 40 (9) ◽  
pp. 1219-1237 ◽  
Author(s):  
H A Sandeman ◽  
B L Cousens ◽  
C J Hemmingway
Keyword(s):  
Lithospheric Mantle ◽  
Primitive Mantle ◽  
Geochemical Data ◽  
Mafic Rocks ◽  
Isotopic Signatures ◽  
Basaltic Rocks ◽  
Depleted Mantle ◽  
Wide Range ◽  
Continental Lithospheric Mantle ◽  
Hurwitz Group

The Paleoproterozoic Hurwitz Group of the western Churchill Province is an erosional remnant of an areally extensive, predominantly shallow-water intracratonic basin comprised of four major sequences. Sequence 2, forming the central part of the stratigraphy, contains the Ameto Formation, a sequence of pillowed and massive basaltic rocks and associated gabbro sills termed the Happotiyik Member that are interlayered with subordinate deep-water mudstones, siltstones, and diamictites. Whole-rock geochemical data for the mafic rocks reveals a suite of homogeneous tholeiitic basalts with affinities to both continental and volcanic-arc tholeiites. Compatible trace elements and large-ion lithophile elements exhibit scattered behavior, whereas all high field strength elements show a systematic increase with Zr. The rocks are large-ion lithophile and light rare-earth element enriched, and have parallel primitive mantle normalized extended trace element patterns with prominent negative Nb, Ta, and Ti anomalies. εNd(t=2200 Ma) values for the rocks range from 0.0 to +0.8. The data indicate that the parental magmas were derived from a heterogeneous, predominantly depleted mantle source that included a minor metasomatically enriched component. Contamination by Neoarchean, juvenile silicic upper crust during ascent was minimal. We envisage that the rocks of the Happotiyik Member were generated from sub-continental lithospheric mantle that was stabilized immediately after formation of the ca. 2680 Ma, Neoarchean Central Hearne sub-domain. This enrichment occurred via metasomatic infiltration of subduction-derived fluids and melts into the overlying lithosphere. A wide range of Paleoproterozoic intra-continental mafic rocks in the western Churchill Province exhibit comparable geochemical and isotopic signatures that suggest an origin in the lithospheric mantle. These observations imply that the Hearne sub-continental lithospheric mantle has endured since the Neoarchean and likely persists today.

scholarly journals Bulk Geochemical Data of Fossil Wood from the Middle Jurassic Clays of Poland

2012 ◽  
Vol 1 (1) ◽  
pp. 71-80 ◽  
Author(s):  
Justyna Smolarek
Keyword(s):  
Organic Matter ◽  
Middle Jurassic ◽  
Fossil Wood ◽  
Short Chain ◽  
Geochemical Data ◽  
Carbonate Content ◽  
Maturity Stage ◽  
Higher Plant ◽  
Wide Range ◽  
Microscopic Studies

Abstract Macroscopic observations, microscopic studies and literature data revealed that Middle Jurassic wood from Częstochowa area has a different state of preservation, and various types and degrees of mineralization and oxidation. Obtained results of organic matter fractionation illustrate a clear domination of polar fraction in the obtained extracts revealing low thermal maturity stage. Total organic carbon (TOC) values for analysed samples are in a wide range from 1.06% to 68.50%. The highest amount of TOC were measured in not or poorly mineralized wood samples but most of them are mineralized wood fragments, showing the TOC values in the range of 2% - 10%. Percentage content of carbonate in fossil wood constitute in a wide range from less than 1% CaCO3 to above 85% CaCO3. The resulting percentage of the total sulfur content is very varied and do not show convergence with other data such as TOC, carbonate content, etc and is most probable connected with pyritisation range. Unlike the Middle Jurassic clay samples, where long-chain and short-chain n-alkanes occur in similar concentrations, in wood samples always short-chain n-alkanes dominated, in the range from 15 to 23 carbon atoms in molecule. The values of the CPI are generally higher than 1 which indicates the contribution of organic matter derived from higher plant waxes, which are characteristic of e.g. needles from gymnosperm plants. Under the influence of post - diagenetic oxidation in mineralized wood samples distribution of n-alkanes is changing. Diaster-13(17)-enes with 28 and 29 carbon atoms in molecule are present in the wood samples, while those with 29 atoms strongly prevail.

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

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late 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.

scholarly journals Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

2001 ◽  
Vol 73 (1) ◽  
pp. 99-119 ◽  
Author(s):  
SILVIA R. MEDEIROS ◽  
CRISTINA M. WIEDEMANN-LEONARDOS ◽  
SIMON VRIEND
Keyword(s):  
Partial Melting ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Tholeiitic Magma ◽  
Rock Types ◽  
Upper Proterozoic ◽  
Incompatible Elements ◽  
Wide Range ◽  
Intermediate Rock

At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

scholarly journals Global whole-rock geochemical database compilation

2019 ◽  
Author(s):  
Matthew Gard ◽  
Derrick Hasterok ◽  
Jacqueline Halpin
Keyword(s):  
Database Management ◽  
Temporal Trends ◽  
Physical Property ◽  
Database Management System ◽  
Geochemical Data ◽  
Data Sets ◽  
Unique Contribution ◽  
Data Set ◽  
Wide Range ◽  
Geochemical Indices

Abstract. Dissemination and collation of geochemical data are critical to promote rapid, creative and accurate research and place new results in an appropriate global context. To this end, we have assembled a global whole-rock geochemical database, with other associated sample information and properties, sourced from various existing databases and supplemented with numerous individual publications and corrections. Currently the database stands at 1,023,490 samples with varying amounts of associated information including major and trace element concentrations, isotopic ratios, and location data. The distribution both spatially and temporally is quite heterogeneous, however temporal distributions are enhanced over some previous database compilations, particularly in terms of ages older than ~ 1000 Ma. Also included are a wide range of computed geochemical indices, physical property estimates and naming schema on a major element normalized version of the geochemical data for quick reference. This compilation will be useful for geochemical studies requiring extensive data sets, in particular those wishing to investigate secular temporal trends. The addition of physical properties, estimated by sample chemistry, represents a unique contribution to otherwise similar geochemical databases. The data is published in .csv format for the purposes of simple distribution but exists in a format acceptable for database management systems (e.g. SQL). One can either manipulate this data using conventional analysis tools such as MATLAB®, Microsoft® Excel, or R, or upload to a relational database management system for easy querying and management of the data as unique keys already exist. This data set will continue to grow, and we encourage readers to contact us or other database compilations contained within about any data that is yet to be included. The data files described in this paper are available at https://doi.org/10.5281/zenodo.2592823 (Gard et al., 2019).

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

Linking data systems into a collaborative pipeline for geochemical data from field to archive

2021 ◽  
Author(s):  
Kerstin Lehnert ◽  
Daven Quinn ◽  
Basil Tikoff ◽  
Douglas Walker ◽  
Sarah Ramdeen ◽  
...  
Keyword(s):  
Analytical Data ◽  
Data System ◽  
Standard Reference Materials ◽  
Data Management System ◽  
Geochemical Data ◽  
Data Repository ◽  
Data Systems ◽  
Raw Data ◽  
Wide Range ◽  
Data Lifecycle

<div> <p>Management of geochemical data needs to consider the sequence of phases in the lifecycle of these data from field to lab to publication to archive. It also needs to address the large variety of chemical properties measured; the wide range of materials that are analyzed; the different ways, in which these materials may be prepared for analysis; the diversity of analytical techniques and instrumentation used to obtain analytical results; and the many ways used to calibrate and correct raw data, normalize them to standard reference materials, and otherwise treat them to obtain meaningful and comparable results. In order to extract knowledge from the data, they are then integrated and compared with other measurements, formatted for visualization, statistical analysis, or model generation, and finally cleaned and organized for publication and deposition in a data repository. Each phase in the geochemical data lifecycle has its specific workflows and metadata that need to be recorded to fully document the provenance of the data so that others can reproduce the results.</p> </div><div> <p>An increasing number of software tools are developed to support the different phases of the geochemical data lifecycle. These include electronic field notebooks, digital lab books, and Jupyter notebooks for data analysis, as well as data submission forms and templates. These tools are mostly disconnected and often require manual transcription or copying and pasting of data and metadata from one tool to the other. In an ideal world, these tools would be connected so that field observations gathered in a digital field notebook, such as sample locations and sampling dates, can be seamlessly send to an IGSN Allocating Agent to obtain a unique sample identifier with a QR code with a single click. The sample metadata would be readily accessible for the lab data management system that allows the researchers to capture information about the sample preparation, and that connects to the instrumentation to capture instrument settings and the raw data. The data would then be seamlessly accessed by data reduction software, visualized, and further compared to data from global databases that can be directly accessed. Ultimately, a few clicks will allow the user to format the data for publication and archiving.</p> </div><div> <p>Several data systems that support different stages in the lifecycle of samples and sample-based geochemical data have now come together to explore the development of standardized interfaces and APIs and consistent data and metadata schemas to link their systems into an efficient pipeline for geochemical data from the field to the archive. These systems include StraboSpot (www.strabospot.org; data system for digital collection, storage, and sharing of both field and lab data), SESAR (<span>www.geosamples.org</span>; sample registry and allocating agent for IGSN), EarthChem (www.earthchem.org; publishers and repository for geochemical data), Sparrow (sparrow-data.org; data system to organize analytical data and track project- and sample-level metadata), IsoBank (isobank.org; repository for stable isotope data), and MacroStrat (macrostrat.org; collaborative platform for geological data exploration and integration).</p> </div>

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