Anatomy of two Permian greenschist- to blueschist-facies tectonic mélanges in the Solonker Suture Zone (Inner Mongolia, northeastern China): evidence for divergent double subduction and soft collision

2020 ◽  
Vol 177 (5) ◽  
pp. 981-996 ◽  
Author(s):  
Huichuan Liu ◽  
Jichun Wang ◽  
Chun-Kit Lai ◽  
Yinglei Li ◽  
Jingfan Wang ◽  
...  
Keyword(s):  
Inner Mongolia ◽  
Northeastern China ◽  
Controversial Issues ◽  
Early Permian ◽  
Content Type ◽  
The Matrix ◽  
Ophiolitic Rocks ◽  
Supplementary Material ◽  
Tectonic Mélange ◽  
East West

The timing and processes of the Paleo-Asian Ocean (PAO) closure are still controversial issues due to ambiguous interpretation of the regional geological records. We describe the structural and kinematic features of two Permian greenschist-/blueschist-facies tectonic mélanges at Zhurihe and Erdaojing in Inner Mongolia (northeastern China), separated by the Solonker Suture. The tectonic mélanges have block-in-matrix fabrics. The Zhurihe tectonic mélange in the south is dominated by NE-trending folds, and east–west- to NE-trending reverse/strike-slip faults, indicating a NW–SE compressive direction. Blocks in the Zhurihe mélange include ophiolitic fragments (c. 292 Ma) and ocean island sequences (c. 274 Ma), which show E-MORB and OIB geochemical affinities, respectively. The matrix includes blueschist, greenschist, quartz schist and clastics, of which the blueschist yielded a zircon U–Pb age of c. 255 Ma, and is geochemically E-MORB-like. The Erdaojing mélange north of the Solonker Suture is dominated by east–west-trending folds, and NE- and NW-trending reverse faults, indicating a north–south compressive orientation. The Erdaojing mélange is composed of early Permian (c. 281 Ma) ophiolite blocks, and middle Permian (c. 266 Ma) actinolite schist and clastics as the matrix. The Erdaojing ophiolitic rocks are geochemically N-MORB tholeiitic. Our results define two parallel Permian MORB-type ophiolitic belts separated by the central Solonker Suture. These observations are evidence for the Permian divergent double subduction and Early Triassic soft-collision model for the PAO along the Solonker Suture.Supplementary material: Detailed analytical methods and results are available at: https://doi.org/10.6084/m9.figshare.c.5008910

scholarly journals Outcrop-scale manifestations of reactivation during multiple superimposed rifting and basin inversion events: the Devonian Orcadian Basin, northern Scotland

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-089 ◽  
Author(s):  
A.M. Dichiarante ◽  
R.E. Holdsworth ◽  
E.D. Dempsey ◽  
K.J.W. McCaffrey ◽  
T.A.G. Utley
Keyword(s):  
Structural Complexity ◽  
Structural Data ◽  
Dominant Group ◽  
Content Type ◽  
Basin Inversion ◽  
Supplementary Material ◽  
Group 2 ◽  
Orcadian Basin ◽  
East West ◽  
Group 1

The Devonian Orcadian Basin in Scotland hosts extensional fault systems assumed to be related to the initial formation of the basin, with only limited post-Devonian inversion and reactivation. However, a recent detailed structural study across Caithness, underpinned by published Re–Os geochronology, shows that three phases of deformation are present. North–south- and NW–SE-trending Group 1 faults are related to Devonian ENE–WSW transtension associated with sinistral shear along the Great Glen Fault during the formation of the Orcadian Basin. Metre- to kilometre-scale north–south-trending Group 2 folds and thrusts are developed close to earlier sub-basin-bounding faults and reflect late Carboniferous–early Permian east–west inversion associated with dextral reactivation of the Great Glen Fault. The dominant Group 3 structures are dextral oblique NE–SW-trending and sinistral east–west-trending faults with widespread syndeformational carbonate mineralization (± pyrite and bitumen) and are dated using Re–Os geochronology as Permian (c. 267 Ma). Regional Permian NW–SE extension related to the development of the offshore West Orkney Basin was superimposed over pre-existing fault networks, leading to local oblique reactivation of Group 1 faults in complex localized zones of transtensional folding, faulting and inversion. The structural complexity in surface outcrops onshore therefore reflects both the local reactivation of pre-existing faults and the superimposition of obliquely oriented rifting episodes during basin development in the adjacent offshore areas.Supplementary material: Stereographic projections of compiled structural data from individual fieldwork localities are available at https://doi.org/10.6084/m9.figshare.c.5115228

scholarly journals Nature and significance of rift-related, near-surface fissure-fill networks in fractured carbonates below regional unconformities

2020 ◽  
Vol 177 (6) ◽  
pp. 1168-1185 ◽  
Author(s):  
Kit Hardman ◽  
Robert E. Holdsworth ◽  
Edward Dempsey ◽  
Ken McCaffrey
Keyword(s):  
Wall Rock ◽  
Surface Phenomenon ◽  
Low Permeability ◽  
Early Permian ◽  
Near Surface ◽  
Content Type ◽  
Basement Rocks ◽  
Supplementary Material ◽  
Fissure Fill ◽  
Migration Pathways

Fissure-fill networks are a widely recognized, but relatively little described, near-surface phenomenon (<1–2 km) hosted in carbonate and crystalline basement rocks below regional unconformities. Faults and fractures in otherwise tight Devonian carbonate basement rocks of the Tor Bay region, Devon, SW England are associated with the development of millimetre- to decametre-wide fissures containing red-coloured early Permian sedimentary material, vuggy calcite mineralization and wall rock collapse breccia. These features preserve evidence about the style and history of fault deformation and reactivation in near-surface settings and on fluid-related processes, such as elutriation and/or mineralization. Field observations, palaeostress analysis and fracture topology analyses show that the rift-related faults and fractures created a network of long-lived open cavities during the development of the Portland–Wight Basin in the early Permian. Once formed, they were subjected to episodic, probably seismically induced, fluid fluxing events and local karstification. The large, well-connected networks of naturally propped fractures were (and possibly still are) important fluid migration pathways within otherwise low-permeability host rocks. These structures are probably equivalent to those observed in many other rift-related, near-surface tectonic settings and suggest that the Tor Bay outcrops can be used as a global analogue for sub-unconformity open fissure systems hosted in low-permeability basement rocks.Supplementary material: Appendix A is available at https://doi.org/10.6084/m9.figshare.c.5023103

Tectonic significance of a supra-ophiolitic sedimentary cover succession, Unst, Shetland, Scottish Caledonides: insights from the U–Pb–Hf detrital zircon record

2021 ◽  
pp. jgs2020-169
Author(s):  
Konstantinos Papapavlou ◽  
Rob A Strachan ◽  
Craig D Storey ◽  
Dean Bullen
Keyword(s):  
Sedimentary Cover ◽  
Detrital Zircons ◽  
Early Paleozoic ◽  
Isotopic Data ◽  
Content Type ◽  
Tectonic Events ◽  
Tectonic Significance ◽  
The Matrix ◽  
Supplementary Material ◽  
Laurentian Margin

The tectonic significance of the Muness Phyllite, which overlies the Unst–Fetlar ophiolite in Shetland, Scottish Caledonides, is poorly understood. U–Pb analyses of detrital zircons show that it was deposited after c. 469 Ma. Early Paleozoic grains have εHf values of −0.3 to +12.3 and were probably derived from the extension of the Midland Valley arc. Psammite clasts and the matrix of the Muness Phyllite contain Proterozoic and Archean detrital zircons with age peaks of c. 1, 1.4–1.5, 1.6–1.7, 1.8–1.9 and 2.7 Ga. These are consistent with ultimate derivation from NE Laurentia sources and were probably recycled from the Neoproterozoic East Mainland Succession that underlies the Mesozoic East Shetland Basin. The Muness Phyllite is interpreted to have been deposited soon after the Grampian I orogeny in a successor basin that overstepped and received detritus from the Midland Valley arc, the East Mainland Succession and the Unst–Fetlar ophiolite. It was then deformed and metamorphosed, probably at c. 450 Ma during the Grampian II orogenic event. The Muness Phyllite therefore provides a record of middle to late Ordovician tectonic events along the Scottish sector of the Laurentian margin following ophiolite obduction.Supplementary material: Analytical details and instrumentation parameters and U–Pb and Lu–Hf isotopic data are available at https://doi.org/10.6084/m9.figshare.c.5324986

Primary tissues dominated ground-level trunk diameter in Sigillaria: evidence from the Wuda Tuff, Inner Mongolia

2021 ◽  
pp. jgs2021-021
Author(s):  
Michael P. D'Antonio ◽  
C. Kevin Boyce ◽  
Wei-Ming Zhou ◽  
Hermann W. Pfefferkorn ◽  
Jun Wang
Keyword(s):  
Inner Mongolia ◽  
Ground Level ◽  
Early Ontogeny ◽  
Internal Anatomy ◽  
Living Plant ◽  
Content Type ◽  
Trunk Diameter ◽  
Primary Body ◽  
Supplementary Material

Arborescent lycopsid stumps are typically fossilized as casts, so that proximal anatomy is rarely available for study. This presents a roadblock for empirically reconstructing their early ontogeny, which requires knowledge of proximal tissue proportions. Here, we describe nine upright, in situ stump casts of Sigillaria from the earliest Permian Wuda Tuff, Inner Mongolia, China that preserve traces of internal anatomy. From these specimens, we interpret thin vasculature and periderm and a broad primary cortex within ∼50 cm of ground level in the living plant. These specimens support recent arguments that periderm production was limited in arborescent lycopsids and that the primary body reached its mature diameter close to ground level rather than distally further up the trunk.Supplementary material: additional figures of specimens and data regarding where measurements were made is available at https://doi.org/10.6084/m9.figshare.c.5558620

The largest arthropod in Earth history: insights from newly discovered Arthropleura remains (Serpukhovian Stainmore Formation, Northumberland, England)

2021 ◽  
pp. jgs2021-115
Author(s):  
Neil S. Davies ◽  
Russell J. Garwood ◽  
William J. McMahon ◽  
Joerg W. Schneider ◽  
Anthony P. Shillito
Keyword(s):  
Atmospheric Oxygen ◽  
Early Carboniferous ◽  
Late Carboniferous ◽  
Three Dimensions ◽  
Early Permian ◽  
Content Type ◽  
Delta Plain ◽  
3D Mesh Model ◽  
Supplementary Material ◽  
Body Fossil

Arthropleura is a genus of giant myriapods that ranged from the early Carboniferous to Early Permian, with some individuals attaining lengths >2 m. Although most of the known fossils of the genus are disarticulated and occur primarily in late Carboniferous (Pennsylvanian) strata, we report here partially articulated Arthropleura remains from the early Carboniferous Stainmore Formation (Serpukhovian; Pendleian) in the Northumberland Basin of northern England. This 76 × 36 cm specimen represents part of an exuvium and is notable because only two comparably articulated giant Arthropleura fossils are previously known. It represents one of the largest known arthropod fossils and the largest arthropleurid recovered to date, the earliest (Mississippian) body fossil evidence for gigantism in Arthropleura, and the first instance of a giant arthropleurid body fossil within the same regional sedimentary succession as the large arthropod trackway Diplichnites cuithensis. The remains represent 12–14 anterior Arthropleura tergites in the form of a partially sand-filled dorsal exoskeleton. The original organism is estimated to have been 55 cm in width and up to 2.63 m in length, weighing c. 50 kg. The specimen is preserved partially in three dimensions within fine sandstone and has been moderately deformed by synsedimentary tectonics. Despite imperfect preservation, the specimen corroborates the hypothesis that Arthropleura had a tough, sclerotized exoskeleton. Sedimentological evidence for a lower delta plain depositional environment supports the contention that Arthropleura preferentially occupied open woody habitats, rather than swampy environments, and that it shared such habitats with tetrapods. When viewed in the context of all the other global evidence for Arthropleura, the specimen contributes to a dataset that shows the genus had an equatorially restricted palaeogeographical range, achieved gigantism prior to late Paleozoic peaks in atmospheric oxygen, and was relatively unaffected by climatic events in the late Carboniferous, prior to its extinction in the early Permian.Supplementary material: Images of 3D mesh model of Arthropleura are available at https://doi.org/10.6084/m9.figshare.c.5715450

Study on high-temperature wear and mechanism of Al-Si/graphite composites prepared by the die-casting process

2020 ◽  
Vol 72 (10) ◽  
pp. 1153-1158 ◽  
Author(s):  
Yafei Deng ◽  
Xiaotao Pan ◽  
Guoxun Zeng ◽  
Jie Liu ◽  
Sinong Xiao ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Peer Review ◽  
Die Casting ◽  
Casting Machine ◽  
Injection Pressure ◽  
Casting Process ◽  
Matrix Alloy ◽  
Content Type ◽  
The Matrix

Purpose This paper aims to improve the tribological properties of aluminum alloys and reduce their wear rate. Design/methodology/approach Carbon is placed in the model at room temperature, pour 680°C of molten aluminum into the pressure chamber, and then pressed it into the mold containing carbon felt through a die casting machine, and waited for it to cool, which used an injection pressure of 52.8 MPa and held the same pressure for 15 s. Findings The result indicated that the mechanical properties of matrix and composite are similar, and the compressive strength of the composite is only 95% of the matrix alloy. However, the composite showed a low friction coefficient, the friction coefficient of Gr/Al composite is only 0.15, which just is two-third than that of the matrix alloy. Similarly, the wear rate of the composite is less than 4% of the matrix. In addition, the composite can avoid severe wear before 200°C, but the matrix alloy only 100°C. Originality/value This material has excellent friction properties and is able to maintain this excellent performance at high temperatures. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0454/

Fatigue behavior of precipitation strengthened Cu–Ni–Si alloy modified by Cr and Zr addition

2020 ◽  
Vol 11 (6) ◽  
pp. 861-873
Author(s):  
Ş. Hakan Atapek ◽  
Spiros Pantelakis ◽  
Şeyda Polat ◽  
Apostolos Chamos ◽  
Gülşah Aktaş Çelik
Keyword(s):  
Design Methodology ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Lower Stress ◽  
Content Type ◽  
Hardened Alloy ◽  
Zr Addition ◽  
Nucleation Sites ◽  
The Matrix ◽  
Lower Stress Level

Purpose The purpose of this paper is to investigate the fatigue behavior of precipitation-strengthened Cu‒2.55Ni‒0.55Si alloy, modified by the addition of 0.25 Cr and 0.25 Zr (wt%), using mechanical and fractographical studies to reveal the effect of microstructural features on the fracture. Design/methodology/approach For strengthening, cast and hot forged alloy was subjected to solution annealing at 900°C for 60 min, followed by quenching in water and then aging at 490°C for 180 min. Precipitation-hardened alloy was exposed to fatigue tests at R=−1 and different stress levels. All fracture surfaces were examined within the frame of fractographical analysis. Findings Fine Ni-rich silicides responsible for the precipitation strengthening were observed within the matrix and their interactions with the dislocations at lower stress level resulted in localized shearing and fine striations. Although, by the addition of Cr and Zr, the matrix consisted of hard Ni, Zr-rich and Cr-rich silicides, these precipitates adversely affected the fatigue behavior acting as nucleation sites for cracks. Originality/value These findings contribute to the present knowledge by revealing the effect of microstructural features on the mechanical behavior of precipitation-hardened Cu‒Ni‒Si alloy modified by Cr and Zr addition.

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