Interaction among upper crustal, lower crustal, and mantle materials in the Port Mouton pluton, Meguma Lithotectonic Zone, southwest Nova Scotia

2000 ◽  
Vol 37 (4) ◽  
pp. 579-600 ◽  
Author(s):  
D Barrie Clarke ◽  
Raymond Fallon ◽  
Larry M Heaman
Keyword(s):  
Nova Scotia ◽  
Lower Crust ◽  
Early Stage ◽  
Late Devonian ◽  
Upper Crust ◽  
Middle Stage ◽  
Two Component ◽  
Granitoid Rocks ◽  
Mafic Magmas ◽  
Lithotectonic Zone

The Port Mouton pluton is unique among the Late Devonian peraluminous granitoid bodies in the Meguma Lithotectonic Zone of southwestern Nova Scotia in its lithological heterogeneity, extensive physical and chemical interaction with the country rocks, clear evidence for mingling and mixing with mafic magmas, and highly abundant pegmatites. New U–Pb age determinations on monazite establish an intrusion age of 373 ± 1 Ma, similar to the ages of other Meguma Lithotectonic Zone granitoid plutons and mafic intrusions. Field relations, petrology, and geochemistry define three stages of intrusion of the Port Mouton pluton: (i) early stage, discontinuously exposed around the outer margin of the pluton, dominated by coarse-grained tonalite-granodiorite, and with Rb/Sr < 0.55, Eu/Eu* > 0.40, and GdN/LuN < 2; (ii) middle stage, occupying the interior of the pluton, dominated by medium-grained granodiorite-monzogranite, and with Rb/Sr > 0.55, Eu/Eu* < 0.40, and GdN/LuN > 2; and (iii) late stage, consisting of abundant minor sheets throughout the pluton, dominated by fine-grained tonalite, granodiorite, and leucogranite that are similar to rocks of the early and middle stages. The Port Mouton pluton shows a wider range of 87Sr/86Sri (0.7036-0.7154), and a wider range and generally higher εNdi (–3.72 to +2.12), than other granitoid rocks in the Meguma Lithotectonic Zone, potentially reflecting a complex, partially equilibrated, interaction among mantle, lower crust, and upper crust. Field, petrological, and chemical evidence for the involvement of mantle-derived magmas and melting of upper crust permit modelling of the Port Mouton pluton granitoid compositions by three simultaneous mixing equations. These mixing model results suggest that the early stage granitoid rocks can form from simple three-component mixing relationships when the bulk distribution coefficients between residuum and melt for Sr and Nd range from 1.05 to 1.18, or two-component mixing combined with fractionation of material like the known felsic lower crust. The middle stage granitoid rocks only yield solutions involving two-component mixing and fractionation of material unlike the known felsic lower crust. We conclude that the Late Devonian mafic magmas played a major role in the formation of granitoid magmas in the Meguma Lithotectonic Zone by supplying heat and material to cause partial fusion of the Avalon lower crust.

Probing the composition of unexposed basement, South Portuguese Zone, southern Iberia: implications for the connections between the Appalachian and Variscan orogens

2012 ◽  
Vol 49 (4) ◽  
pp. 591-613 ◽  
Author(s):  
James A. Braid ◽  
J. Brendan Murphy ◽  
Cecilio Quesada ◽  
Luke Bickerton ◽  
James K. Mortensen
Keyword(s):  
Lower Crust ◽  
Late Paleozoic ◽  
Magmatic Zircon ◽  
Late Devonian ◽  
Upper Crust ◽  
Isotope Data ◽  
Variscan Orogen ◽  
Southern Iberia ◽  
Meguma Terrane ◽  
The Relationship

Geochemistry and Sm–Nd and U–Pb (magmatic zircon) isotope data from a postcollisional batholith that crosscuts the allochthonous South Portuguese Zone (SPZ) of southern Iberia suggest that the basement is compositionally more juvenile than the exposed upper crust. The SPZ is an allochthonous terrane of the late Paleozoic Variscan orogen. The oldest exposed units in the SPZ are Late Devonian continental clastics, and as a result, the origins of the SPZ are unknown. Multifaceted inherited zircon cores from a granitoid batholith (Sierra Norte Batholith, SNB) reveal Neoproterozoic (ca. 561–647 Ma) and Mesoproterozoic ages (ca. 1075 – ca. 1116 Ma). Granitoid samples are characterized by εNd values ranging from +1.4 to –9.6 and model ages ca. 0.76–1.8 Ga. Conversely, the exposed Late Devonian clastics of the SPZ are characterized by more negative εNd values (–7.5 to –10.4). Taken together, U–Pb and Sm–Nd data indicate the lower crust that melted to yield the SNB was (i) Neoproterozoic (ca. 560–650 Ma) to Mesoproterozoic (ca. 1.0–1.2 Ga) in age, (ii) was not compositionally similar to the overlying Devono-Carboniferous continental detritus but was instead more juvenile, with model ages between ca. 0.9–1.2 Ga. This unusual relationship is similar to the relationship between the relatively juvenile basement and ancient upper crust documented in the exposed portion of the Meguma terrane in the northern Appalachians, which paleogeographic reconstructions show was immediately outboard of southern Iberia in the Late Devonian.

On the Antarctic Peninsula batholith

1995 ◽  
Vol 132 (4) ◽  
pp. 399-412 ◽  
Author(s):  
P. T. Leat ◽  
J. H. Scarrow ◽  
I. L. Millar
Keyword(s):  
Antarctic Peninsula ◽  
Early Cretaceous ◽  
Lower Crust ◽  
Sedimentary Rocks ◽  
Central Zone ◽  
Upper Crust ◽  
Partial Fusion ◽  
Partial Melts ◽  
Mafic Magmas ◽  
The Antarctic

AbstractThe plutonic rocks of the Antarctic Peninsula magmatic arc form one of the major batholiths of the circum-Pacific rim. The Antarctic Peninsula batholith is a 1350 km long by < 210 km wide structure which was emplaced over the period ˜240 to 10 Ma, with a Cretaceous peak of activity that started at 142 Ma and waned during the Late Cretaceous. Early Jurassic and Late Jurassic–Early Cretaceous gaps in intrusive activity probably correspond to episodes of arc compression. In a northern zone of the Antarctic Peninsula, the batholith intrudes Palaeozoic–Mesozoic low-grade meta-sedimentary rocks, and in a central zone it intrudes schists and ortho- and paragneisses which have Late Proterozoic Nd model ages and were deformed during Triassic to Early Jurassic compression. In a southern zone the oldest exposed rocks are Permian sedimentary rocks and deformed Jurassic volcanic and sedimentary rocks. All these pre-batholith rocks formed a belt of relatively immature crust along the Gondwana margin. With few exceptions, Jurassic plutons crop out only within the central zone: many are peraluminous, having ‘S-like’ mineralogies and relatively high 87sr/86sri. They are considered to consist largely of partial melts of upper crust schists and gneisses and components of mafic magmas that caused the partial fusion. By contrast, Early Cretaceous plutons crop out along the length of the batholith. Few magma compositions appear to have been affected by upper crust, the bulk being compositionally independent of the type of country rock they intrude. They are dominated by metaluminous, calcic, Si-oversaturated, 1-type granitoid rocks with relatively low 87sr/86sri intermediate-silicic compositions (< 5% MgO). We interpret these to represent partial melts of basic to intermediate, igneous, locally garnet-bearing, lower crust. Contemporaneous mafic magmas (e.g. syn-plutonic dykes) form a more alkaline, Si-saturated series having higher 143Nd/144Nd at the same87sr/86sr than the intermediate-silicic series, to which they are not petrogenetically related. The change from limited partial fusion of upper crust in Jurassic times to widespread partial fusion of lower crust in Early Cretaceous times is considered to be a result of an increasing volume of basaltic intrusion into the crust with time.

Analysis of Chinese herbal formulae recommended for COVID-19 in different schemes in China: A data mining Approach

2020 ◽  
Vol 23 ◽  
Author(s):  
LiWei Yin ◽  
YaCen Gao ◽  
ZiPing Li ◽  
MengYu Wang ◽  
KaiXin Chen
Keyword(s):  
Data Mining ◽  
Early Stage ◽  
Herbal Medicines ◽  
Chinese Herbs ◽  
Recovery Stage ◽  
Prescription Pattern ◽  
Middle Stage ◽  
Chinese Herbal ◽  
Severe Stage ◽  
Herbal Formulae

Background: Novel coronavirus pneumonia (NCP), or coronavirus disease 2019 (COVID-19), is a worldwide health threat that has affected millions of people globally. Traditional Chinese medicine (TCM) has been introduced for the treatment of COVID-19. However, efficacy differs among herbal medicines, and the ideal prescription pattern for TCM herbal formulae for COVID-19 treatment needs to be explored. Therefore, the data mining method has been used in this study to analyze the TCM prescription pattern for COVID-19. Objective: The aim of this study was to analyze the TCM prescription pattern in Regional Schemes in China for COVID-19 in order to provide a new reference for the use of TCM in COVID-19 treatment. Method: By searching the TCM treatment protocols of COVID-19 in 23 Regional Schemes, TCM syndromes and herbal medicines were analyzed by data mining. The Ancient and Modern Medical Case Cloud Platform (V2.1 personal Edition) was used to perform frequency statistics, correlation analysis, and cluster analysis. A total of 82 TCM syndromes and 171 Chinese herbal medicines were found. The course of the disease can be divided into the early stage, middle stage, severe stage, and recovery stage. Results: In the early stage, the focus is primarily on resolving dampness, dispelling cold, and diffusing the lungs. In the middle stage, the treatment priority is clearing heat and resolving toxins, promoting lung function, and relieving asthma. In the severe stage, the focus is on tonifying Qi, restoring Yang, and relieving depletion of Yin and Yang. In the recovery stage, the main treatment is to invigorate the spleen and regulate Qi, tonify Qi, nourish Yin, and clear residual disease evil. There are certain differences between the Regional Schemes and the Nation Schemes, but the core prescription pattern of the former is consistent with the latter. The effectiveness of these 171 Chinese herbs include but are not limited to inhibiting COVID-19, strengthening immune system function, preventing heart failure, acting as antioxidants, oxidative stress inhibitory effects, maintaining organ function, and improving leukocyte survival. Conclusion: This study may help to improve understanding of TCM herbal prescription pattern, practices, reveal the efficacy of combinations of Chinese herbs, and provide new ideas for TCM treatment for COVID-19.

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.

Results of a seismic reflection survey across the fault zone between the Thompson nickel belt and the Churchill Tectonic Province, northern Manitoba

1981 ◽  
Vol 18 (1) ◽  
pp. 13-25 ◽  
Author(s):  
A. G. Green
Keyword(s):  
Fault Zone ◽  
Lower Crust ◽  
Seismic Reflection ◽  
High Amplitude ◽  
Small Scale ◽  
Upper Crust ◽  
Travel Times ◽  
Reflection Point ◽  
Point Data ◽  
Amplitude Reflection

Approximately 11 km of four-fold common reflection point data have been recorded across a region that spans the contact fault zone between the Thompson nickel belt and the Churchill Tectonic Province. From these data it is shown that the upper crust in this region and, to a lesser extent, the lower crust are characterized by numerous scattered events that originate from relatively small-scale features. Within the Thompson nickel belt two extensive and particularly high-amplitude reflection zones, at two-way travel times of t = 5.0–5.5 s and t = 6.0–6.5 s, are recorded with apparent northwesterly dips of 0–20 °C. These reflection zones, which have a laminated character, are truncated close to the faulted contact with the Churchill Province. Both the contact fault zone and the Churchill Province in this region have crustal sections that are relatively devoid of significant reflectors. The evidence presented here confirms that the crustal section of the Thompson nickel belt is fundamentally different from that of the Churchill Tectonic Province.

Geochemistry of the Namurian Lismore Formation, northern mainland Nova Scotia: sedimentation and tectonic activity along the southern flank of the Maritimes Basin

1999 ◽  
Vol 36 (10) ◽  
pp. 1655-1669 ◽  
Author(s):  
Jacquelyn E Stevens ◽  
J Brendan Murphy ◽  
Fred W Chandler
Keyword(s):  
Nova Scotia ◽  
Tectonic Activity ◽  
Isotopic Data ◽  
Rock Fragments ◽  
Metasedimentary Rocks ◽  
Clastic Rocks ◽  
Granitoid Rocks ◽  
Maritimes Basin ◽  
Group B ◽  
Southern Flank

Geochemical and isotopic data from the clastic rocks of the Namurian Lismore Formation in mainland Nova Scotia identify key episodes of tectonic activity during the development of the Maritimes Basin in Atlantic Canada. The Lismore Formation forms part of the Mabou Group and is an upward-coarsening 2500 m thick fluvial sequence deposited in the Merigomish sub-basin along the southern flank of the Maritimes Basin. Based on stratigraphic evidence, the Lismore Formation can be divided into upper and lower members which reflect variations in depositional environment and paleoclimate. The geochemical and isotopic data may also be subdivided into two groupings that primarily reflect varying contributions from accessory phases, clay minerals, or rock fragments. This subdivision occurs 115 m above the base of the upper member. The data from the lower grouping (group A) show an important contribution from underlying Silurian rocks, with a relatively minor contribution from Late Devonian granitoid rocks from the adjacent Cobequid Highlands and possibly metasedimentary rocks from the Meguma Terrane to the south. The data from the upper grouping (group B) reveal a more important contribution from the Cobequid Highlands granitoid rocks. This variation in geochemistry is thought to constrain the age of renewed motion and uplift along the faults along the southern flank of the Maritimes Basin and, more generally, suggests that geochemical and isotopic data of continental clastic rocks may help constrain the age of tectonic events that influence deposition of basin-fill rocks.

Dynamics of the extension in the Fonualei Rift in the northern Lau Basin at 16 °S

2021 ◽  
Author(s):  
Anna Jegen ◽  
Anke Dannowski ◽  
Heidrun Kopp ◽  
Udo Barckhausen ◽  
Ingo Heyde ◽  
...  
Keyword(s):  
Velocity Gradient ◽  
Lower Crust ◽  
Pacific Plate ◽  
P Wave ◽  
Upper Crust ◽  
Lau Basin ◽  
Australian Plate ◽  
The Pacific ◽  
Refraction Seismic ◽  
Roll Back

&lt;p&gt;The Lau Basin is a young back-arc basin steadily forming at the Indo-Australian-Pacific plate boundary, where the Pacific plate is subducting underneath the Australian plate along the Tonga-Kermadec island arc. Roughly 25 Ma ago, roll-back of the Kermadec-Tonga subduction zone commenced, which lead to break up of the overriding plate and thus the formation of the western Lau Ridge and the eastern Tonga Ridge separated by the emerging Lau Basin.&lt;/p&gt;&lt;p&gt;As an analogue to the asymmetric roll back of the Pacific plate, the divergence rates decline southwards hence dictating an asymmetric, V-shaped basin opening. Further, the decentralisation of the extensional motion over 11 distinct spreading centres and zones of active rifting has led to the formation of a composite crust formed of a microplate mosaic. A simplified three plate model of the Lau Basin comprises the Tonga plate, the Australian plate and the Niuafo'ou microplate. The northeastern boundary of the Niuafo'ou microplate is given by two overlapping spreading centres (OLSC), the southern tip of the eastern axis of the Mangatolu Triple Junction (MTJ-S) and the northern tip of the Fonualei Rift spreading centre (FRSC) on the eastern side. Slow to ultraslow divergence rates were identified along the FRSC (8-32 mm/a) and slow divergence at the MTJ (27-32 mm/a), both decreasing southwards. However, the manner of divergence has not yet been identified. Additional regional geophysical data are necessary to overcome this gap of knowledge.&lt;/p&gt;&lt;p&gt;Research vessel RV Sonne (cruise SO267) set out to conduct seismic refraction and wide-angle reflection data along a 185 km long transect crossing the Lau Basin at ~16 &amp;#176;S from the Tonga arc in the east, the overlapping spreading centres, FRSC1 and MTJ-S2, and extending as far as a volcanic ridge in the west. The refraction seismic profile consisted of 30 ocean bottom seismometers. Additionally, 2D MCS reflection seismic data as well as magnetic and gravimetric data were acquired.&lt;/p&gt;&lt;p&gt;The results of our P-wave traveltime tomography show a crust that varies between 4.5-6 km in thickness. Underneath the OLSC the upper crust is 2-2.5 km thick and the lower crust 2-2.5 km thick. The velocity gradients of the upper and lower crust differ significantly from tomographic models of magmatically dominated oceanic ridges. Compared to such magmatically dominated ridges, our final P-wave velocity model displays a decreased velocity gradient in the upper crust and an increased velocity gradient in the lower crust more comparable to tectonically dominated rifts with a sparse magmatic budget.&lt;/p&gt;&lt;p&gt;The dominance of crustal stretching in the regional rifting process leads to a tectonical stretching, thus thinning of the crust under the OLSC and therefore increasing the lower crust&amp;#8217;s velocity gradient. Due to the limited magmatic budget of the area, neither the magnetic anomaly nor the gravity data indicate a magmatically dominated spreading centre. We conclude that extension in the Lau Basin at the OLSC at 16 &amp;#176;S is dominated by extensional processes with little magmatism, which is supported by the distribution of seismic events concentrated at the northern tip of the FRSC.&lt;/p&gt;

scholarly journals Relationships between Pathological Patterns and Quality of Life: Pathway Analysis

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Shin-Woong Cho ◽  
Young-Jae Park ◽  
Sang-Chul Lee ◽  
Jaemin Ryu ◽  
Young-Bae Park ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Pathway Analysis ◽  
Early Stage ◽  
General Health Questionnaire ◽  
Blood Stasis ◽  
Health Questionnaire ◽  
Pathway Model ◽  
Middle Stage ◽  
Yin Deficiency

Purpose.The purpose of our study was to examine the relationships between pathological patterns and self-rated quality of life (QoL).Methods.A total of 426 Korean subjects participated in this study (male : female = 154 : 272). The subjects were asked to complete Yin Deficiency (YD), Qi Deficiency (QD), Food Stagnation (FS), Blood Stasis (BS), Phlegm, and Seven Emotions Impairment (SEI) pattern Questionnaires and the General Health Questionnaire (GHQ). We formed a pathway model consisting of pathological patterns and QoL questionnaire scores and examined which pathological patterns resulted in decreased QoL using path analysis.Results.Our pathway model had satisfactory fitness levels (GFI = 0.975, NFI = 0.984, and CFI = 0.984) and showed that Phlegm and SEI patterns directly resulted in decreased QoL, whereas QD, YD, FD, and BS indirectly resulted in decreased QoL. The pathway model suggested that the severity or stage of decreased QoL may be estimated by pathological patterns: QD and YD patterns are associated with the early stage; FS and BS patterns are associated with the middle stage; Phlegm and SEI are associated with the later stage of decreased QoL.Conclusion.Our results suggest that pathological patterns directly or indirectly affect decreases in QoL.

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