المؤلفون: Andrew R.C. Kylander-Clark, Catherine Mottram, John M. Cottle

المصدر: Mottram, C M, Cottle, J M & Kylander-Clark, A 2018, ' Campaign-style U-Pb titanite petrochronology: along-strike variations in timing of metamorphism in the Himalayan Metamorphic Core ', Geoscience Frontiers . https://doi.org/10.1016/j.gsf.2018.09.007Test
Geoscience Frontiers, Vol 10, Iss 3, Pp 827-847 (2019)

مصطلحات موضوعية: Mineral, 010504 meteorology & atmospheric sciences, Lithology, Metamorphic rock, lcsh:QE1-996.5, Geochemistry, Metamorphism, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, lcsh:Geology, Tectonics, Titanite, engineering, Erosion, General Earth and Planetary Sciences, Accretion (geology), Geology, 0105 earth and related environmental sciences

الوصف: Present-day along-strike heterogeneities within the Himalayan orogen are seen at many scales, from variations within the deep architecture of the lithospheric mantle, to differences in geomorphologic surface processes. Here, we present an internally consistent petrochronologic dataset from the Himalayan metamorphic core (HMC), in order to document and investigate the causes of along-strike variations in its Oligocene–Miocene tectonic history. Laser ablation split-stream analysis was used to date and characterise the geochemistry of titanite from 47 calc-silicate rocks across >2000 km along the Himalaya. This combined U-Pb-REE-Zr single mineral dataset circumvents uncertainties associated with interpretations based on data compilations from different studies, mineral systems and laboratories, and allows for direct along-strike comparisons in the timing of metamorphic processes. Titanite dates range from ∼30 Ma to 12 Ma, recording (re-)crystallization between 625 °C and 815 °C. Titanite T-t data overlap with previously published P-T-t paths from interleaved peltic rocks, demonstrating the usefulness of titanite petrochronology for recording the metamorphic history in lithologies not traditionally used for thermobarometry. Overall, the data indicate a broad eastward-younging trend along the orogen. Disparities in the duration and timing of metamorphism within the HMC are best explained by along-strike variations in the position of ramps on the basal detachment controlling a two-stage process of preferential ductile accretion at depth followed by the formation of later upper-crust brittle duplexes. These processes, coupled with variable erosion, resulted in the asymmetric exhumation of a younger, thicker crystalline core in the eastern Himalaya. Keywords: Himalaya, Petrochronology, Titanite, Metamorphic petrology

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::647e3bd4a798cfa73251a33b109717cfTest
https://doi.org/10.1016/j.gsf.2018.09.007Test

المؤلفون: Jason Harvey, Bradley R. Hacker, Christy B. Till, Graham Hagen-Peter, Frank J. Spera, John M. Cottle, Gareth G.E. Seward, M. A. Edwards, Jenna V. Adams, Andrew R.C. Kylander-Clark, Matthew G. Jackson

المصدر: Edwards, M A, Jackson, M G, Kylander-Clark, A R C, Harvey, J, Hagen-Peter, G A, Seward, G G E, Till, C B, Adams, J V, Cottle, J M, Hacker, B R & Spera, F J 2019, ' Extreme enriched and heterogeneous 87 Sr/ 86 Sr ratios recorded in magmatic plagioclase from the Samoan hotspot ', Earth and Planetary Science Letters, vol. 511, pp. 190-201 . https://doi.org/10.1016/j.epsl.2019.01.040Test

مصطلحات موضوعية: Olivine, 010504 meteorology & atmospheric sciences, Subduction, Terrigenous sediment, mantle heterogeneity, Geochemistry, Ocean island basalt, LASS, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Geophysics, Space and Planetary Science, Geochemistry and Petrology, Isotope geochemistry, Hotspot (geology), isotope geochemistry, Earth and Planetary Sciences (miscellaneous), engineering, Plagioclase, LA-ICP-MS, mantle geochemistry, Geology, 0105 earth and related environmental sciences

الوصف: We report the major-element, trace-element, and 87 Sr/ 86 Sr compositions of six plagioclase crystals from two Samoan lavas with extreme EM2 isotopic compositions (ALIA-115-18 with whole-rock 87 Sr/ 86 Sr of 0.718592, and ALIA-115-21 with whole-rock 87 Sr/ 86 Sr of 0.720469). We employed laser-ablation split-stream mass spectrometry (LASS) to simultaneously measure 87 Sr/ 86 Sr ratios, major-element concentrations, and trace-element concentrations in the same plagioclase crystal volume. We find that two plagioclase crystals have extreme 87 Sr/ 86 Sr heterogeneity in excess of 5000 ppm (where ppm of 87 Sr/Sr variability86=10 6 ⋅[Sr/8687Sr max − 87 Sr/ 86 Sr min ]/ 87 Sr/ 86 Sr avg ). In two of the plagioclase crystals, we identify the highest 87 Sr/ 86 Sr ratios (0.7224) ever measured in any fresh, mantle-derived ocean island basalt (OIB) or OIB-hosted mineral phase. We find that in 87 Sr/ 86 Sr-versus-Sr concentration space, the six plagioclase crystals overlap in a “common component” region with higher 87 Sr/ 86 Sr than has been previously identified in whole-rock Samoan lavas or mineral separates. We use the occurrence of olivine mineral inclusions (Fo=74.5±0.8, 2 SD) in the high- 87 Sr/ 86 Sr zone of one plagioclase crystal to infer the bulk composition (Mg#=46.8±0.8, 2 SD) of the extreme EM2 magma from which the olivine and high- 87 Sr/ 86 Sr plagioclase crystallized. We argue that a relatively evolved EM2 endmember magma mixed with at least one lower- 87 Sr/ 86 Sr melt to generate the observed intra-crystal plagioclase isotopic heterogeneity. By inferring that subducted terrigenous sediment gives rise to EM2 signatures in Samoan lavas, we estimate that the quantity of sediment necessary to generate the most-elevated 87 Sr/ 86 Sr ratios observed in the Samoan plagioclase is ∼7% of the mantle source. We also estimate that sediment subduction into the mantle over geologic time has generated a sediment domain that constitutes 0.02% of the mass of the mantle, a much lower proportion than required in the EM2 mantle source. Even if subducted sediment is concentrated in large low-shear-velocity provinces (LLSVPs) at the base of the mantle (which constitute up to 7.7% of the mantle's mass), then only 0.25% of the LLSVPs are composed of sediment. This requires that the distribution of subducted sediment in the mantle is heterogeneous, and the high relative abundance of sediment in the Samoan EM2 mantle is an anomalous relic of ancient subduction that has survived convective attenuation.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::9318c742e94007e1ef7038615e2f9625Test
https://doi.org/10.1016/j.epsl.2019.01.040Test

المؤلفون: J. M. Benítez-Pérez, P. Castiñeiras, J. Gómez-Barreiro, J. R. Martínez Catalán, A. Kylander-Clark, R. Holdsworth

المصدر: Solid Earth, 2020, Vol.11(6), pp.2303-2325 [Peer Reviewed Journal]
Solid Earth, Vol 11, Pp 2303-2325 (2020)
E-Prints Complutense: Archivo Institucional de la UCM
Universidad Complutense de Madrid
E-Prints Complutense. Archivo Institucional de la UCM
instname

مصطلحات موضوعية: Provenance, Geodinámica, 010504 meteorology & atmospheric sciences, Stratigraphy, Metamorphic rock, Geochemistry, Soil Science, Metamorphism, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, lcsh:Stratigraphy, Geochemistry and Petrology, Titanite, 0105 earth and related environmental sciences, Earth-Surface Processes, lcsh:QE640-699, lcsh:QE1-996.5, Petrología, Paleontology, Geology, Granulite, lcsh:Geology, Geophysics, Monazite, Geochronology, engineering, Geoquímica, Zircon

الوصف: The Sobrado unit, within the upper part of the Órdenes Complex (NW Spain) represents an allochthonous tectonic slice of exhumed high-grade metamorphic rocks formed during a complex sequence of orogenic processes in the middle to lower crust. In order to constrain those processes, U–Pb geochronology and rare-earth element (REE) analyses of accessory minerals in migmatitic paragneiss (monazite, zircon) and mylonitic amphibolites (titanite) were conducted using laser ablation split stream inductively coupled plasma mass spectrometry (LASS-ICP-MS). The youngest metamorphic zircon age obtained coincides with a Middle Devonian concordia monazite age (∼380 Ma) and is interpreted to represent the minimum age of the Sobrado high-P granulite facies metamorphism that occurred during the early stages of the Variscan orogeny. Metamorphic titanite from the mylonitic amphibolites yield a Late Devonian age (∼365 Ma) and track the progressive exhumation of the Sobrado unit. In zircon, cathodoluminescence images and REE analyses allow two aliquots with different origins in the paragneiss to be distinguished. An Early Ordovician age (∼490 Ma) was obtained for metamorphic zircons, although with a large dispersion, related to the evolution of the rock. This age is considered to mark the onset of granulite facies metamorphism in the Sobrado unit under intermediate-P conditions, and related to intrusive magmatism and coeval burial in a magmatic arc setting. A maximum depositional age for the Sobrado unit is established in the late Cambrian (∼511 Ma). The zircon dataset also record several inherited populations. The youngest cogenetic set of zircons yields crystallization ages of 546 and 526 Ma which are thought to be related to the peri-Gondwanan magmatic arc. The additional presence of inherited zircons older than 1000 Ma is interpreted as suggesting a West African Craton provenance.

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::dbf43fd30c485d061798bcd60ef2669dTest
https://se.copernicus.org/articles/11/2303/2020Test/

المؤلفون: Robert E. Holdsworth, José R. Martínez Catalán, Juan Gómez-Barreiro, J. M. Benitez-Perez, Andrew R.C. Kylander-Clark, Pedro Castiñeiras

مصطلحات موضوعية: Provenance, biology, Geochemistry, Metamorphism, Orogeny, engineering.material, biology.organism_classification, Titanites, Monazite, Titanite, Geochronology, engineering, Geology, Zircon

الوصف: The Sobrado unit, within the upper part of the Órdenes complex (NW Iberia) represents an allochthonous tectonic slice of exhumed high grade metamorphic rocks formed during a complex sequence of orogenic processes in the middle to lower crust. In order to constrain those processes, U-Pb geochronology and REE analyses of accessory minerals in migmatitic paragneisses (monazite, zircon), and mylonitic amphibolites (titanite) were conducted using LASS-ICP-MS. The youngest metamorphic zircon age obtained co-incides with a Middle Devonian concordia monazite age (~ 385 Ma) and is interpreted to represent the minimum age of the Sobrado high-P granulite-facies metamorphism that occurred during the early stages of the Variscan Orogeny. Metamorphic titanites from the mylonitic amphibolites yield a Late Devonian age (~ 365 Ma), and track the progressive exhumation of the Sobrado unit. In zircon, cathodoluminescence images and REE analyses allow two aliquots with different origins in the paragneiss to be distinguished. An Early Ordovician age (~ 490 Ma) was obtained for metamorphic zircons, employing the TuffZirc algorithm, although with a large analytical dispersion. This age is considered to mark the onset of granulite-facies metamorphism in the Sobrado unit under intermediate-P conditions, and related to intrusive magmatism and coeval burial in a magmatic arc setting. A maximum depositional age for the Sobrado unit is established in the late Cambrian (~ 503 Ma). The zircon dataset also record several inherited populations. The youngest cogenetic set of zircons yield a crystallization age from TuffZirc algorithm of ~ 530 Ma and are thought to be related to the peri-Gondwana magmatic arc. The additional presence of inherited zircons older than ~ 530 Ma is interpreted as suggesting a West African Craton provenance.

وصف الملف: application/pdf

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::bb6f75857fefb005ec2c070d16aa0407Test
https://doi.org/10.5194/se-2020-38Test

المؤلفون: Gültekin Topuz, Winfried H. Schwarz, Rainer Altherr, Aral I. Okay, Gürsel Sunal, Andrew R.C. Kylander-Clark

المصدر: Lithos. :121-135

مصطلحات موضوعية: Blueschist, Incompatible element, 010504 meteorology & atmospheric sciences, Greenschist, Geochemistry, Metamorphism, Geology, engineering.material, 010502 geochemistry & geophysics, Ophiolite, 01 natural sciences, Phengite, Igneous rock, Geochemistry and Petrology, Titanite, engineering, 0105 earth and related environmental sciences

الوصف: The Eastern Mediterranean region within the Tethyan belt is characterised by two main pulses of suprasubduction-zone ophiolite formation during the Early–Middle Jurassic and Late Cretaceous. Despite vast exposures of the Permo-Triassic accretionary complexes, related suprasubduction-zone ophiolites and the timing of subduction initiation leading to the formation of Permo-Triassic accretionary complexes are unknown so far. Here we report on a ~ 40 km long and 0.3 to 1.8 km wide metaophiolite fragment within transitional greenschist- to blueschist-facies oceanic rocks from NW Turkey. The metaophiolite fragment is made up mainly of serpentinite and minor dykes or stocks of strongly sheared metagabbro with mineral assemblages involving actinolite/winchite, chlorite, epidote, albite, titanite and phengite. The metagabbro displays (i) variable CaO and MgO contents, (ii) anomalously high Mg# (= 100 ∗ molar MgO/(MgO + FeOtot)) of 75–88, and (iii) positive Eu anomalies, together with low contents of incompatible elements such as Ti, P and Zr, suggesting derivation from former plagioclase cumulates. The serpentinites comprise serpentine, ± chlorite, ± talc, ± calcite and relict Cr-Al spinel surrounded by ferrichromite to magnetite. Relict Cr-Al spinels are characterised by (i) Cr/(Cr + Al) ratios of 0.45–0.56 and Mg/(Mg + Fe2 +) ratio of 0.76–0.22, (ii) variable contents of ZnO and MnO, and (iii) extremely low TiO2 contents. Zn and Mn contents are probably introduced into Cr-Al spinels during greenschist- to blueschist metamorphism. Compositional features of the serpentinite such as (i) Ca- and Al-depleted bulk compositions, (ii) concave U-shaped, chondrite-normalised rare earth element patterns (REE) with enrichment of light and heavy REEs, imply that serpentinites were probably derived from depleted peridotites which were refertilised by light rare earth element enriched melts in a suprasubduction-zone mantle wedge. U-Pb dating on igneous zircons from three metagabbro samples indicates igneous crystallisation at 262 Ma (middle Permian). Timing of the metamorphism is constrained by incremental 40Ar/39Ar dating on phengitic white mica at 201 Ma (latest Triassic). We conclude that the metaophiolite represents a fragment of middle Permian suprasubduction-zone oceanic lithosphere, involved in a latest Triassic subduction zone. These data, together with several reports in literature, indicate that the middle Permian was a time of suprasubduction-zone ophiolite formation in the Tethyan belt.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::66007232f7e2a1a6e8416bddbe143f1fTest
https://doi.org/10.1016/j.lithos.2017.12.005Test

المؤلفون: Kyle T. Ashley, Mark J. Caddick, Calvin A. Mako, Sarah E. Mazza, John M. Cottle, Richard D. Law, Andrew R.C. Kylander-Clark, J. Ryan Thigpen

المصدر: Precambrian Research. 355:106089

مصطلحات موضوعية: 010504 meteorology & atmospheric sciences, Metamorphic rock, Geochemistry, Metamorphism, Geology, Orogeny, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, Geochemistry and Petrology, Monazite, Geochronology, Titanite, engineering, Metasomatism, 0105 earth and related environmental sciences, Zircon

الوصف: Accessory phase geochronology records several phases of metamorphism that affected Moine metasedimentary rocks in the Northern Highlands Terrane of Scotland. Within the Sgurr Beag nappe, monazite and xenotime record initial metamorphism at c. 750 Ma, with later resetting at c. 600 Ma and c. 425 Ma. Monazite, xenotime, titanite and zircon also cryptically record c. 750 Ma and c. 600 Ma metamorphism in the Naver and Ben Hope nappes prior to the dominant 435-415 Ma Scandian orogeny. Textural, geochemical, and isotopic data indicate that c. 600 Ma and c. 425 Ma isotopic resetting in the Sgurr Beag nappe was caused by fluid-mediated dissolution and reprecipitation of monazite and xenotime. The compositions of fluid-altered monazite fall into two distinct trends, with high and low Y+HREE apparently reflecting the distinct timing and temperature conditions of dissolution and reprecipitation. Monazite-xenotime thermometry is applied to constrain the temperatures of fluid alteration. High Y+HREE, low Th/U monazite is related to high temperature (∼650°C) alteration at c. 600 Ma and low Y+HREE, high Th/U monazite is related to lower temperature (∼400°C) reactivity at c. 425 Ma. These data show that the composition of reprecipitated monazite is sensitive to metamorphic conditions during fluid alteration and is therefore useful in understanding the evolution of polyphase metamorphic terranes. These data suggest that a widespread metamorphic or metasomatic event affected northern Scotland at c. 600 Ma, likely related to higher heat flux and magmatic activity during the break-up of Rodinia. Additionally, the now adjacent Sgurr Beag and Moine nappes appear to have contrasting metamorphic records at least until Caledonian orogenesis, which suggests that final regional scale motion on the Sgurr Beag thrust must be of Caledonian age.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::cc92e15bc13bbfaaa0a0b91a55b6dde0Test
https://doi.org/10.1016/j.precamres.2020.106089Test

المؤلفون: Bradley R. Hacker, Andrew R.C. Kylander-Clark, Michael A. Stearns, Joshua M. Garber, Gareth G.E. Seward

المصدر: Journal of Petrology. 58:1031-1057

مصطلحات موضوعية: 010504 meteorology & atmospheric sciences, Metamorphic rock, Geochemistry, Trace element, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, Geophysics, Geochemistry and Petrology, Titanite, engineering, Petrology, Geology, 0105 earth and related environmental sciences

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::aa5146b1dac508403c20376e19da71a8Test
https://doi.org/10.1093/petrology/egx046Test

المؤلفون: Andrew R.C. Kylander-Clark

المصدر: Reviews in Mineralogy and Geochemistry. 83:183-198

مصطلحات موضوعية: Mineral, 010504 meteorology & atmospheric sciences, Geochemistry, Mineralogy, Electron microprobe, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, law.invention, Secondary ion mass spectrometry, Igneous rock, Marine chronometer, Geochemistry and Petrology, law, Titanite, engineering, Inductively coupled plasma mass spectrometry, Geology, 0105 earth and related environmental sciences, Zircon

الوصف: Petrochronology is a field of Earth science in which the isotopic and / or elemental composition of a mineral chronometer is interpreted in combination with its age, thus yielding a more synergistic combination of petrology and chronology that can be used to interpret geologic processes. It has recently attracted renewed interest as technologies for mineral analysis have improved. Examples are many, and continue to grow, from the early adoption of U / Th ratios in zircon as an indicator for magmatic vs. igneous crystallization (e.g., Ahrens 1965), to using the Nd isotopic composition in titanite to track source contribution over time (see Applications ; B. R. Hacker, personal communication). Age and chemical information can be obtained by a variety of techniques: electron microprobe (age; major and minor elements; see Williams et al. 2017), secondary ion mass spectrometry (SIMS; age; trace elements; isotopic ratios; see Schmitt and Vazquez 2017), and laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS; age; trace elements; isotopic ratios). Laser-ablation ICPMS instrumentation and techniques, the focus of this chapter, have been employed as a petrochronologic tool for decades, starting with separate analyses of ages and elemental and / or isotopic compositions, which were then combined and interpreted. For example, Zheng et al. (2009) employed LA-ICPMS to analyze the trace-element (TE) chemistry, Hf isotopic composition, and age of zircons from kimberlites by using three spots on each zircon grain, one for each type of analysis. This work was relatively time consuming and expensive, given the required number of analytical sessions, but yielded far better confidence in the conclusions, because of the link between physical conditions (petrology) and time (chronology). Instrumentation and techniques which employ LA-ICPMS have continued to improve, particularly in the ease with which petrochronologic data can be obtained. A single LA-ICPMS instrument can now measure both the …

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::499ea3a71788a283bf5ccf272b2f0b1dTest
https://doi.org/10.2138/rmg.2017.83.6Test

المؤلفون: Andrew R.C. Kylander-Clark, Robert M. Holder, Bradley R. Hacker, Gareth G.E. Seward

المصدر: Contributions to Mineralogy and Petrology. 174

مصطلحات موضوعية: 010504 meteorology & atmospheric sciences, Metamorphic rock, Mineralogy, engineering.material, 010502 geochemistry & geophysics, Thermal diffusivity, 01 natural sciences, Thermochronology, Geophysics, Geochemistry and Petrology, Geochronology, Titanite, engineering, Diffusion (business), Closure temperature, Geology, 0105 earth and related environmental sciences, Solid solution

الوصف: Length scales of compositional heterogeneity in titanite from 750 to 1000 °C metamorphic rocks from southern Madagascar were measured to provide empirical constraints on elemental diffusivities. The calculated Pb diffusivity is comparable to experimental estimates of Sr diffusivity; because of this, U–Pb dates from rocks that reached peak temperatures 900 °C; thus, Zr-in-titanite thermobarometry should not be reset by diffusion in all but the smallest grains in the hottest rocks. Al and Nb diffuse at similar rates to Zr. Ce and Fe diffuse slower than Pb, but faster than Zr. Differences in empirical and experimental estimates of elemental diffusivities might be related to the complexity of most natural titanite solid solutions compared to the near-end-member titanite used in experiments.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::df61498ad2ec2f12a828f5a49594a009Test
https://doi.org/10.1007/s00410-019-1578-2Test

المؤلفون: Bradley R. Hacker, Andrew R.C. Kylander-Clark, Gareth G.E. Seward, Robert M. Holder

المصدر: Geological Society of America Abstracts with Programs.

مصطلحات موضوعية: Titanite, engineering, Geochemistry, engineering.material, Geology

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::2341411ac0e6b2645d838d79362705e2Test
https://doi.org/10.1130/abs/2019am-336931Test