scholarly journals Whole-rock lithogeochemistry, Nd-Hf isotopes, and in situ zircon geochemistry of VMS-related felsic rocks, Finlayson Lake VMS district, Yukon

2021 ◽  
Author(s):  
M J Manor ◽  
S J Piercey
Keyword(s):  
Crustal Melting ◽  
Melt Mixing ◽  
Isotopic Signatures ◽  
Volcanogenic Massive Sulphide ◽  
Lake Formation ◽  
Mineral Scale ◽  
Back Arc ◽  
Finlayson Lake ◽  
Felsic Rocks

The Finlayson Lake district in southeastern Yukon is composed of a Late Paleozoic arc-backarc system that consists of metamorphosed volcanic, plutonic, and sedimentary rocks of the Yukon-Tanana and Slide Mountain terranes. These rocks host >40 Mt of polymetallic resources in numerous occurrences and styles of volcanogenic massive sulphide (VMS) mineralization. Geochemical and isotopic data from these rocks support previous interpretations that volcanism and plutonism occurred in arc-marginal arc (e.g., Fire Lake formation) and continental back-arc basin environments (e.g., Kudz Ze Kayah formation, Wind Lake formation, and Wolverine Lake group) where felsic magmatism formed from varying mixtures of crust- and mantle-derived material. The rocks have elevated high field strength element (HFSE) and rare earth element (REE) concentrations, and evolved to chondritic isotopic signatures, in VMS-proximal stratigraphy relative to VMS-barren assemblages. These geochemical features reflect the petrogenetic conditions that generated felsic rocks and likely played a role in the localization of VMS mineralization in the district. Preliminary in situ zircon chemistry supports these arguments with Th/U and Hf isotopic fingerprinting, where it is interpreted that the VMS-bearing lithofacies formed via crustal melting and mixing with increased juvenile, mafic magmatism; rocks that were less prospective have predominantly crustal signatures. These observations are consistent with the formation of VMS-related felsic rocks by basaltic underplating, crustal melting, and basalt-crustal melt mixing within an extensional setting. This work offers a unique perspective on magmatic petrogenesis that underscores the importance of integrating whole-rock with mineral-scale geochemistry in the characterization of VMS-related stratigraphy.

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the Yukon–Tanana Terrane in the Finlayson Lake Region, Yukon, Canada

2003 ◽  
Vol 40 (1) ◽  
pp. 77-97 ◽  
Author(s):  
Stephen J Piercey ◽  
James K Mortensen ◽  
Robert A Creaser
Keyword(s):  
Isotope Geochemistry ◽  
Volcanic Rocks ◽  
Lake Region ◽  
Volcanogenic Massive Sulphide ◽  
Depleted Mantle ◽  
Intrusive Rocks ◽  
Felsic Volcanic ◽  
Back Arc ◽  
Finlayson Lake ◽  
Felsic Rocks

Devonian–Mississippian felsic rocks from the Finlayson Lake region have variable geochemical and Nd isotopic characteristics that provide insights into the tectonic and metallogenic evolution of the Yukon–Tanana terrane (YTT), and the northern Cordillera. Late Devonian (~365–360 Ma) calc-alkaline and tholeiitic arc felsic rocks in the mafic-dominated Fire Lake unit yield εNd350 = –4.8 and +0.1, respectively, and have 1.49–1.94 Ga depleted mantle model ages (TDM). Devonian–Mississippian (~360–356 Ma) felsic volcanic (Kudz Ze Kayah unit, Wolverine succession) and intrusive rocks (Grass Lakes suite) associated with volcanogenic massive sulphide (VMS) deposits have εNd350 = –7.8 to –9.5 with TDM = 1.59–2.25 Ga. A granitoid sample from the Early Mississippian (~350–345 Ma) Simpson Range plutonic suite has εNd350 = –12.9 and TDM = 2.01 Ga, similar to previously reported values for this suite. The VMS-associated Grass Lakes suite of granitoids has higher high field strength element (HFSE) and rare-earth element (REE) contents, and higher Zr/Sc, Zr/TiO2, Nb/La, and Zr/La values relative to the Simpson Range plutonic suite; these geochemical features are similar to coeval VMS-associated felsic volcanic rocks in the Kudz Ze Kayah unit. The identification of similar HFSE–REE-enriched felsic volcanic and subvolcanic intrusive rocks may aid in delineating prospective regions for VMS mineralization in the YTT and other continental-margin arc to back-arc environments. The geochemical and Nd isotopic data for these YTT felsic rocks suggest that they reflect episodic mid-Paleozoic arc (Fire Lake unit; Simpson Range plutonic suite) and back-arc magmatism (Kudz Ze Kudz unit; Wolverine succession) built upon a transitional basement with variable, but significant, influence from evolved (Proterozoic) crustal materials.

In-situ reaction-replacement origin of hornblendites in the Early Cretaceous Laiyuan complex, North China Craton, and implications for its tectono-magmatic evolution

2021 ◽  
Author(s):  
Jia Chang ◽  
Andreas Audétat ◽  
Jian-Wei Li
Keyword(s):  
Partial Melting ◽  
North China Craton ◽  
Lithospheric Mantle ◽  
Lower Crust ◽  
North China ◽  
Ultramafic Rocks ◽  
Magmatic Evolution ◽  
Mafic Magmas ◽  
Felsic Rocks

Abstract Two suites of amphibole-rich mafic‒ultramafic rocks associated with the voluminous intermediate to felsic rocks in the Early Cretaceous Laiyuan intrusive-volcanic complex (North China Craton) are studied here by detailed petrography, mineral- and melt inclusion chemistry, and thermobarometry to demonstrate an in-situ reaction-replacement origin of the hornblendites. Moreover, a large set of compiled and newly obtained geochronological and whole-rock elemental and Sr-Nd isotopic data are used to constrain the tectono-magmatic evolution of the Laiyuan complex. Early mafic‒ultramafic rocks occur mainly as amphibole-rich mafic‒ultramafic intrusions situated at the edge of the Laiyuan complex. These intrusions comprise complex lithologies of olivine-, pyroxene- and phlogopite-bearing hornblendites and various types of gabbroic rocks, which largely formed by in-situ crystallization of hydrous mafic magmas that experienced gravitational settling of early-crystallized olivine and clinopyroxene at low pressures of 0.10‒0.20 GPa (∼4‒8 km crustal depth); the hornblendites formed in cumulate zones by cooling-driven crystallization of 55‒75 vol% hornblende, 10‒20 vol% orthopyroxene and 3‒10 vol% phlogopite at the expense of olivine and clinopyroxene. A later suite of mafic rocks occurs as mafic lamprophyre dikes throughout the Laiyuan complex. These dikes occasionally contain some pure hornblendite xenoliths, which formed by reaction-replacement of clinopyroxene at high pressures of up to 0.97‒1.25 GPa (∼37‒47 km crustal depth). Mass balance calculations suggest that the olivine-, pyroxene- and phlogopite-bearing hornblendites in the early mafic‒ultramafic intrusions formed almost without melt extraction, whereas the pure hornblendites brought up by lamprophyre dikes required extraction of ≥ 20‒30 wt% residual andesitic to dacitic melts. The latter suggests that fractionation of amphibole in the middle to lower crust through the formation of reaction-replacement hornblendites is a viable way to produce adakite-like magmas. New age constraints suggest that the early mafic-ultramafic intrusions formed during ∼132‒138 Ma, which overlaps with the timespan of ∼126‒145 Ma recorded by the much more voluminous intermediate to felsic rocks of the Laiyuan complex. By contrast, the late mafic and intermediate lamprophyre dikes were emplaced during ∼110‒125 Ma. Therefore, the voluminous early magmatism in the Laiyuan complex was likely triggered by the retreat of the flat-subducting Paleo-Pacific slab, whereas the minor later, mafic to intermediate magmas may have formed in response to further slab sinking-induced mantle thermal perturbations. Whole-rock geochemical data suggest that the early mafic magmas formed by partial melting of subduction-related metasomatized lithospheric mantle, and that the early intermediate to felsic magmas with adakite-like signatures formed from mafic magmas through strong amphibole fractionation without plagioclase in the lower crust. The late mafic magmas seem to be derived from a slightly different metasomatized lithospheric mantle by lower degrees of partial melting.

scholarly journals In-Situ Synthesis and Property Evaluation of High-Density Polyethylene Reinforced Groundnut Shell Particulate Composite

2021 ◽  
Vol 6 (4) ◽  
pp. 305-311
Author(s):  
Abdulmumin Adebisi ◽  
Tajudeen Mojisola ◽  
Umar Shehu ◽  
Muhammed Sani Adam ◽  
Yusuf Abdulaziz
Keyword(s):  
Tensile Strength ◽  
Water Absorption ◽  
Impact Energy ◽  
High Density Polyethylene ◽  
In Situ Synthesis ◽  
High Density ◽  
Compression Moulding ◽  
Melt Mixing ◽  
Groundnut Shell

In-situ synthesis of high-density polyethylene (HDPE) reinforced groundnut shell particulate (GSP) composite with treated GSP within the range of 10-30 wt% at 10 wt% has been achieved. The adopted technique used in the production of the composite is melt mixing and compounding using two roll mills with a compression moulding machine. Properties such as hardness, tensile strength, impact energy and water absorption analysis were examined. The result revealed that addition of GSP increases the hardness value from 22.3 to 87 Hv. However, the tensile strength progressively decreased as the GSP increases in the HDPE. This trend arises due to the interaction between neighbouring reinforced particulate which appears to influence the matrix flow, thereby inducing embrittlement of the polymer matrix. It was also observed that water absorption rate steadily increased with an increase in the exposure time and the absorbed amount of water increases by increasing the wt% of the GSP. Analysing the obtained results, it was concluded that there were improvements in the hardness, tensile strength, impact energy and water absorption properties of the HDPE-GSP polymer composite when compared to unreinforced HDPE. On these premises, GSP was found as a promising reinforcement which can positively influence the HDPE properties of modern composites.

Microstructure and Mechanical Properties of In Situ TiB2/6061 Composites

2012 ◽  
Vol 535-537 ◽  
pp. 14-17
Author(s):  
Long Hua Zhong ◽  
Yu Tao Zhao ◽  
Song Li Zhang ◽  
Rong Wen
Keyword(s):  
Master Alloy ◽  
Volume Fraction ◽  
X Ray Diffraction ◽  
Melt Mixing ◽  
X Ray ◽  
Mixing Method ◽  
Particulate Volume Fraction ◽  
Ti Powder ◽  
Particulate Volume

In situ TiB2/6061 composites have been successfully synthesized through chemical reaction between 6061 master alloy, Al-3B master alloy and Ti powder. The composites fabricated by direct melt mixing method was investigated by Scanning Electron Microscope (SEM), Energy Dispersive x-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), The results shown the existence of TiB2particles. The size of most TiB2particles were just in micron level, and even reached to sub-micron level. The increase in microhardness and tensile strength for the as-prepared composites with 5% particulate volume fraction (PVF) are up to 26.8% and 51.2% respectively.

Passive-margin magmatism caused by enhanced slab-pull forces in central Tibet

Geology ◽  
2020 ◽  
Author(s):  
Wei Dan ◽  
Qiang Wang ◽  
William M. White ◽  
Xian-Hua Li ◽  
Xiu-Zheng Zhang ◽  
...  
Keyword(s):  
Passive Margin ◽  
Lower Plate ◽  
Isotopic Signatures ◽  
Ridge Subduction ◽  
Slab Rollback ◽  
Element Enrichment ◽  
Central Tibet ◽  
Back Arc ◽  
Ocean Ridge ◽  
Qiangtang Terrane

We report on a ca. 239 Ma mafic dike swarm intruded in the Southern Qiangtang terrane, central Tibet, that was generated on the passive continental margin of a subducting lower plate. The dikes are tholeiitic basalts and exhibit light rare earth element enrichment, modest negative anomalies in Nb and Ta, and enriched isotopic signatures. The dikes are coeval with a back-arc basin formed in the upper plate as a result of the rollback of the Paleo-Tethys oceanic slab. Thus, after ocean-ridge subduction, enhanced slab-pull forces related to slab rollback on one side of the ocean induced extension and magmatism in the passive margin on the opposite side. We argue that enhanced slab-pull forces are a previously unrecognized mechanism for the generation of lower-plate passive-margin magmatism.

Back-arc basin evolution in the southern Lhasa sub-terrane, southern Tibet: Constraints from U-Pb ages and in-situ Lu-Hf isotopes of detrital zircons

2019 ◽  
Vol 185 ◽  
pp. 104026 ◽  
Author(s):  
Yuanku Meng ◽  
Walter D. Mooney ◽  
Yuan Ma ◽  
Han Xu ◽  
Rongzhen Tang
Keyword(s):  
Detrital Zircons ◽  
Hf Isotopes ◽  
Basin Evolution ◽  
Southern Tibet ◽  
Back Arc

Structure-Property Relationships of Poly(Butylene Terephthalate)/Polyolefin Blends

1998 ◽  
Vol 18 (1-2) ◽  
pp. 17-30 ◽  
Author(s):  
D.S. Lee ◽  
J.K. Doo ◽  
B. Kim ◽  
J. Kim
Keyword(s):  
Particle Size ◽  
Room Temperature ◽  
Structure Property ◽  
Melt Mixing ◽  
Butylene Terephthalate ◽  
Polyolefin Blends ◽  
Structure Property Relationships ◽  
Acrylic Ester ◽  
Discrete Phase

Abstract Structure-property relationships of poly(butylene terephthalate) (PBT) / polyolefin (PO) (80/20) blends modified by a reactive compatibilizer, ethylene-acrylic ester-glycidyl methacrylate terpolymer (BAG), were investigated as part of studies on toughening of PBT. POs used for the study were ethylene propylene rubber (EPR), low-density polyethylene (LDPE), and high-density polyethylene (HDPE), whose deformabilities were different at room temperature. It was observed that the particle size of PO in the discrete phase was the smallest when the EAG content was 8~12 wL%. Shear viscosity of the blends increased as the particle size was decreased. It seems that the morphology and rheological properties of the blends were affected by graft copolymers formed in situ from EAG and PBT during melt mixing. Brittle-tough transition of impact strength of the PBT/EPR/EAG blends was observed when the EAG content was increased from 0 to 4 wt% at room temperature. However, blends of PBT/LDPE/EAG and PBT/HDPE/EAG showed brittle-tough transition with increasing the EAG content from 8 wt% to 12 wt%. It is postulated that toughening of the PBT depends on the deformability of the discrete PO particle as well as its size.

Multi-stage crustal melting from Late Permian back-arc extension through Middle Triassic continental collision to Late Triassic post-collisional extension in the East Kunlun Orogen

Lithos ◽  
2020 ◽  
Vol 360-361 ◽  
pp. 105446 ◽  
Author(s):  
Xu Zhao ◽  
Junhao Wei ◽  
Lebing Fu ◽  
Jan Marten Huizenga ◽  
M. Santosh ◽  
...  
Keyword(s):  
Middle Triassic ◽  
Continental Collision ◽  
Late Triassic ◽  
Crustal Melting ◽  
Late Permian ◽  
East Kunlun ◽  
Multi Stage ◽  
Back Arc

Subduction polarity of the Ailaoshan Ocean (eastern Paleotethys): Constraints from detrital zircon U-Pb and Hf-O isotopes for the Longtan Formation

2019 ◽  
Vol 132 (5-6) ◽  
pp. 987-996
Author(s):  
Xiao-Ping Xia ◽  
Jian Xu ◽  
Chao Huang ◽  
Xiaoping Long ◽  
Meiling Zhou
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
South China Block ◽  
The South ◽  
Forearc Basin ◽  
Isotopic Signatures ◽  
Northeastern Japan ◽  
O Isotopes ◽  
A Minor ◽  
Back Arc

Abstract The Paleotethys Ailaoshan Ocean separated the South China and Indochina blocks during the late Paleozoic. Uncertainty remains regarding subduction of this ocean—whether it was subducted eastward beneath the South China block or westward beneath the Indochina block. In this study, we present new detrital zircon U-Pb age, and Hf and O isotope data from the Longtan Formation, which was recognized to be deposited before the ocean closed. Our results show that the formation can be divided into three units: Unit 1 is distributed west of the suture and dominates the area; it contains major age peaks at 290–250 Ma and minor multiple old age peaks. Unit 2 consists of a minor distribution west of the suture, and it shows a dominant 250 Ma age peak; old zircons are very few or not present. Their Hf and O isotopic signatures are similar to those of unit 1. Unit 3 is distributed east of the suture and is characterized by a single distinct ca. 240 Ma age peak with almost no Precambrian zircons. We interpret that units 1 and 2 were likely deposited in a back-arc and forearc basin, respectively, and a volcanic arc developed on the eastern margin of the Indochina block, similar to the present-day northeastern Japan arc. Meanwhile, unit 3 was likely deposited in a forearc basin on the western margin of the South China block. Therefore, the Ailaoshan Ocean may undergone bipolar subduction both westward and eastward beneath the Indochina and South China blocks, respectively.

scholarly journals A multi-level strategy for anticipating future glacier lake formation and associated hazard potentials

2010 ◽  
Vol 10 (2) ◽  
pp. 339-352 ◽  
Author(s):  
H. Frey ◽  
W. Haeberli ◽  
A. Linsbauer ◽  
C. Huggel ◽  
F. Paul
Keyword(s):  
Swiss Alps ◽  
Bed Topography ◽  
Aster Gdem ◽  
Digital Elevation ◽  
Lake Formation ◽  
Level 3 ◽  
Multi Level ◽  
Four Levels ◽  
Elevation Model

Abstract. In the course of glacier retreat, new glacier lakes can develop. As such lakes can be a source of natural hazards, strategies for predicting future glacier lake formation are important for an early planning of safety measures. In this article, a multi-level strategy for the identification of overdeepened parts of the glacier beds and, hence, sites with potential future lake formation, is presented. At the first two of the four levels of this strategy, glacier bed overdeepenings are estimated qualitatively and over large regions based on a digital elevation model (DEM) and digital glacier outlines. On level 3, more detailed and laborious models are applied for modeling the glacier bed topography over smaller regions; and on level 4, special situations must be investigated in-situ with detailed measurements such as geophysical soundings. The approaches of the strategy are validated using historical data from Trift Glacier, where a lake formed over the past decade. Scenarios of future glacier lakes are shown for the two test regions Aletsch and Bernina in the Swiss Alps. In the Bernina region, potential future lake outbursts are modeled, using a GIS-based hydrological flow routing model. As shown by a corresponding test, the ASTER GDEM and the SRTM DEM are both suitable to be used within the proposed strategy. Application of this strategy in other mountain regions of the world is therefore possible as well.

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