Competence and lithostratigraphy of host rocks govern kimberlite pipe morphology

2018 ◽  
Vol 55 (2) ◽  
pp. 130-137
Author(s):  
David E. Newton ◽  
Amy G. Ryan ◽  
Luke J. Hilchie
Keyword(s):  
Host Rock ◽  
Sedimentary Rock ◽  
Kimberlite Pipe ◽  
Crystalline Rock ◽  
Experimental Results ◽  
Compressed Air ◽  
Unconsolidated Sediments ◽  
Final Shape ◽  
Class 1 ◽  
Host Rocks

We use analogue experimentation to test the hypothesis that host rock competence primarily determines the morphology of kimberlite pipes. Natural occurrences of kimberlite pipes are subdivided into three classes: class 1 pipes are steep-sided diatremes emplaced into crystalline rock; class 2 pipes have a wide, shallow crater emplaced into sedimentary rock overlain by unconsolidated sediments; class 3 pipes comprise a steep-sided diatreme with a shallow-angled crater emplaced into competent crystalline rock overlain by unconsolidated sediments. We use different configurations of three analogue materials with varying cohesions to model the contrasting geological settings observed in nature. Pulses of compressed air, representing the energy of the gas-rich head of a kimberlitic magma, are used to disrupt the experimental substrate. In our experiments, the competence and configuration of the analogue materials control the excavation processes as well as the final shape of the analogue pipes: eruption through competent analogue strata results in steep-sided analogue pipes; eruption through weak analogue strata results in wide, shallow analogue pipes; eruption through intermediate strength analogue strata results in analogue pipes with a shallow crater and a steep-sided diatreme. These experimental results correspond with the shapes of natural kimberlite pipes, and demonstrate that variations in the lithology of the host rock are sufficient to generate classic kimberlite pipe shapes. These findings are consistent with models that ascribe the pipe morphologies of natural kimberlites to the competence of the host rocks in which they are emplaced.

scholarly journals Magma Mixing Genesis of the Mafic Enclaves in the Qingshanbao Complex of Longshou Mountain, China: Evidence from Petrology, Geochemistry, and Zircon Chronology

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Coarse Grained ◽  
Calc Alkaline ◽  
Quartz Crystals ◽  
Alkaline Rocks ◽  
Mafic Enclaves ◽  
Normal Zoning ◽  
Host Rocks

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.

Research on a Novel Miniature Air Compressor Generating both Compressed Air and Vacuum

2014 ◽  
Vol 1027 ◽  
pp. 253-256
Author(s):  
Jian Hai Han ◽  
Jie Zhang ◽  
Dong Liao Fu ◽  
Zhi Gang Hu
Keyword(s):  
Vacuum Pump ◽  
Operating Principle ◽  
Experimental Results ◽  
System Structure ◽  
Compressed Air ◽  
The Novel ◽  
Pump Mode ◽  
Air Compressor

A new kind of miniature air compressor is proposed in this paper. This compressor can produce both compressed air and vacuum. The system structure, operating principle and experimental characteristics of the novel miniature air compressor are described in detail. The experimental results prove that the shift between air compressor mode and vacuum pump mode is possible and the design of system structure is appropriate.

Compositional variation in the chevkinite group: new data from igneous and metamorphic rocks

2009 ◽  
Vol 73 (5) ◽  
pp. 777-796 ◽  
Author(s):  
R. Macdonald ◽  
H. E. Belkin ◽  
F. Wall ◽  
B. Baginski
Keyword(s):  
Electron Microprobe ◽  
Host Rock ◽  
Metamorphic Rocks ◽  
Compositional Variation ◽  
Temperature Range ◽  
Wide Range ◽  
Host Rocks ◽  
Cation Sites ◽  
Dominant Cation

AbstractElectron microprobe analyses are presented of chevkinite-group minerals from Canada, USA, Guatemala, Norway, Scotland, Italy and India. The host rocks are metacarbonates, alkaline and subalkaline granitoids, quartz-bearing pegmatites, carbonatite and an inferred K-rich tuff. The analyses extend slightly the range of compositions in the chevkinite group, e.g. the most MgO-rich phases yet recorded, and we report two further examples where La is the dominant cation in the A site. Patchily- zoned crystals from Virginia and Guatemala contain both perrierite and chevkinite compositions. The new and published analyses are used to review compositional variation in minerals of the perrierite subgroup, which can form in a wide range of host rock compositions and over a substantial pressure- temperature range. The dominant substitutions in the various cation sites and a generalized substitution scheme are described.

scholarly journals Permeability Changes Resulting from Quartz Precipitation and Dissolution around Upper Crustal Intrusions

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Samuel W. Scott ◽  
Thomas Driesner
Keyword(s):  
Host Rock ◽  
Permeability Reduction ◽  
Rock Permeability ◽  
Permeability Changes ◽  
Order Of Magnitude ◽  
Porosity And Permeability ◽  
Fluid Convection ◽  
Flow Heat ◽  
Primary Porosity ◽  
Host Rocks

It has long been recognized that quartz precipitation from circulating hydrothermal fluids may reduce porosity and permeability near intrusions. However, the magnitude of permeability changes and potential feedbacks between flow, heat transfer, and quartz precipitation/dissolution remain largely unquantified. Here, we present numerical simulations of fluid convection around upper crustal intrusions which explicitly incorporate the feedback between quartz solubility and rock permeability. As groundwater is heated to ~350°C, silica dissolves from the host rock, increasing porosity and permeability. Further heating to supercritical conditions leads to intensive quartz precipitation and consequent permeability reduction. The initial host rock permeability and porosity are found to be main controls on the magnitude and timescales of permeability changes. While the permeability changes induced by quartz precipitation are moderate in host rocks with a primary porosity ≥ 0.05, quartz precipitation may reduce rock permeability by more than an order of magnitude in host rocks with a primary porosity of 0.025. Zones of quartz precipitation transiently change locations as the intrusion cools, thereby limiting the clogging effect, except for host rocks with low initial porosity. This permeability reduction occurs in timescales of hundreds of years in host rocks with initial high permeability and thousands of years in host rocks with intermediate permeability.

Underground Research Laboratories in Japan: What Are the Important Factors for Facilities Design?

2003 ◽  
Author(s):  
T. Sato ◽  
S. Mikake ◽  
M. Sakamaki ◽  
K. Aoki ◽  
S. Yamasaki ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Sedimentary Rock ◽  
Mechanical Stability ◽  
Ventilation System ◽  
Sedimentary Rocks ◽  
Crystalline Rock ◽  
Ventilation Network ◽  
Main Stage ◽  
Middle Stage ◽  
Ventilation Shaft

This paper describes the current status of two Japanese off-site Underground Research Laboratories (URLs) Projects, one for crystalline rock and the other for sedimentary rock. This paper is focused on mechanical stability and ventilation, important factors relevant to the design and construction of deep underground facilities. High-pressure inflow, another important factor, will be included in the URL project for crystalline rock. The site of the URL project for crystalline rock is located in Mizunami, Gifu, in the central part of the main island of Japan. The regional geology consists of the Tertiary and Quaternary sedimentary rocks overlying Cretaceous granitic basement. Surface-based investigations, including geological mapping, a seismic refraction survey and shallow borehole investigations, and site preparation at the MIU (Mizunami Underground Research Laboratory) Project site have started in 2002. Numerical analysis is carried out to understand mechanical stability around the openings. The ventilation system design is based on numerical analysis using a ventilation network model. Grouting against the high-pressure inflow is planned. Conceptual design for the MIU at present is as follows: • Two 1,000 m shafts, a Main Shaft (6.5m φ) and a Ventilation shaft (4.5m φ); • Two experimental levels, the Main Stage at 1,000 m and the Middle Stage, at 500 m depths. The site of the URL project for sedimentary rock is located in Horonobe, Hokkaido, north of the main island of Japan. The geology consists of Tertiary sedimentary rocks. Surface-based investigation phase started in 2001. Numerical analysis is carried out to understand mechanical stability of the openings, and to design support. The numerical analysis using ventilation network model is carried out to design the ventilation system and disaster prevention method. Conceptual design for the Hnb-URL at present is as follows: • Two 500 m shafts and a Ventilation shaft; • Two experimental levels, the Main Stage at 500 m and the Middle Stage at 250 m depths.

scholarly journals Characterizing mineralogy and redox reactivity in potential host rocks for a UK geological disposal facility

2015 ◽  
Vol 79 (6) ◽  
pp. 1353-1367 ◽  
Author(s):  
J. Quirke ◽  
C. M. B. Henderson ◽  
R. A. D. Pattrick ◽  
K. M. Rosso ◽  
A. Dent ◽  
...  
Keyword(s):  
Iron Content ◽  
Host Rock ◽  
Azo Dye ◽  
Total Iron ◽  
Geological Disposal ◽  
Potential Host ◽  
Fine Grained ◽  
Reducing Conditions ◽  
Redox Reactivity ◽  
Host Rocks

AbstractGeological disposal facilities (GDF) are intended to isolate and contain radioactive waste within multiple protective barriers, deep underground, to ensure that no harmful quantities of radioactivity reach the surface environment. The last line of defense in a multi-barrier GDF is the geosphere, where iron is present in the host rock mineralogy as either Fe(II) or Fe(III), and in groundwater as Fe(II) under reducing conditions. The mobility of risk-driving radionuclides, including uranium and technetium, in the environment is affected significantly by their valence state. Due to its low redox potential, Fe(II) can mediate reduction of these radionuclides from their oxidized, highly mobile, soluble state to their reduced, insoluble state, preventing them from reaching the biosphere. Here a study of five types of potential host rocks, two granitoids, an andesite, a mudstone and a clay-rich carbonate, is reported. The bulk rocks and their minerals were analysed for iron content, Fe(II/III) ratio, and for the speciation and fine-grained nature of alteration product minerals that might have important controls on groundwater interaction. Total iron content varies between 0.9% in clays to 5.6% in the andesite. X-ray absorption spectroscopy reveals that Fe in the granitoids and andesite is predominantly Fe(II), and in mudstones, argillaceous limestone and terrestrial sandstone is predominantly Fe(III). The redox reactivity of the potential host rocks both in the presence and absence of Fe(II)-containing 'model' groundwater was investigated using an azo dye as a probe molecule. Reduction rates as determined by reactivity with the azo dye were correlated with the ability of the rocks to uptake Fe(II) from groundwater rather than with initial Fe(II) content. Potential GDF host rocks must be characterized in terms of mineralogy, texture, grain size and bulk geochemistry to assess how they might interact with groundwater. This study highlights the importance of redox reactivity, not just total iron and Fe(II)/(III) ratio, when considering the host rock performance as a barrier material to limit transport of radionuclides from the GDF.

Which Processes could define Temperature Limits on the Outer Surface of a Container in a Disposal Facility ?

2020 ◽  
Author(s):  
Guido Bracke ◽  
Eva Hartwig-Thurat ◽  
Jürgen Larue ◽  
Artur Meleshyn ◽  
Torben Weyand ◽  
...  
Keyword(s):  
Outer Surface ◽  
Site Selection ◽  
Selection Process ◽  
Temperature Limit ◽  
Crystalline Rock ◽  
Safety Concept ◽  
Disposal Facility ◽  
High Level ◽  
A Site ◽  
Host Rocks

<p>When the recommencement of the search for and selection of a site for a disposal facility for HLRW in Germany was stipulated by the Site Selection Act (StandAG 2017) in 2017, a <strong>precautionary </strong>temperature limit of 100 °C on the outer surface of the containers with high-level radioactive waste in the disposal facility section was set. This <strong>precautionary </strong>temperature limit shall be applied in preliminary safety analyses provided that the “maximum physically possible temperatures” in the respective host rocks have not yet been determined due to pending research. Therefore, this issue is addressed and discussed in this paper, contributing to “pending research” by a review of the literature.</p><p>This presentation briefly discusses a few examples of thermohydraulical, mechanical, chemical and biological processes in a disposal facility, because temperature limits are derived based on safety impacts regarding THMCB-processes. The temperature-dependent processes have been extracted from databases for features, events and processes (FEP-databases). Furthermore, it is dicussed if the feasibility to retrieve and recover HLRW is hampered at high temperatures.</p><p>It is concluded that a design temperature concerning single components of a disposal facility for the preservation of their features can be derived when a safety concept is established. However, the interactions of all relevant processes in a disposal concept must be considered to determine a specific temperature limit for the outer surface of the containers. Therefore, applicable temperature limits may vary for particular safety and disposal concepts in the following host rocks: rock salt, clay stone and crystalline rock.</p><p>Technical solutions for retrieval and design options for recovery seem to be viable up to temperatures of 200 °C with different, sometimes severe, downsides according to expert judgement.</p><p>It is summarized that emperature limits regarding the outer surface of the containers can be derived specifically for each safety concept and design of the disposal facility in a host rock. General temperature limits without reference to specific safety concepts or the particular design of the disposal facility may narrow down the possibilities for optimisation of the disposal facility and could adversely affect the site selection process in finding the best suitable site.</p>

2D thermo-mechanical-chemical coupled numerical models of interactions between a cooling magma chamber and a visco-elastic host rock

2020 ◽  
Author(s):  
Dániel Kiss ◽  
Evangelos Moulas ◽  
Lisa Rummel ◽  
Boris Kaus
Keyword(s):  
Magma Chamber ◽  
Host Rock ◽  
Numerical Models ◽  
Bulk Composition ◽  
Inertial Forces ◽  
Volume Changes ◽  
Consistent System ◽  
Host Rocks ◽  
2D Numerical Model ◽  
Crustal Magma

<p>A recent focus of studies in geodynamic modeling and magmatic petrology is to understand the coupled behavior between deformation and magmatic processes. Here, we present a 2D numerical model of an upper crustal magma (or mush) chamber in a visco-elastic host rock, with coupled thermal, mechanical and chemical (TMC) processes. The magma chamber is isolated from deeper sources of magma and it is cooling, and thus shrinking. We quantify the mechanical interaction between the shrinking magma chamber and the surrounding host rock, using a compressible visco-elastic formulation, considering several geometries of the magma chamber.</p><p>We present a self-consistent system of the conservation equations for coupled TMC processes, under the assumptions of slow (negligible inertial forces), visco-elastic deformation and constant chemical bulk composition. The thermodynamic melting/crystallization model is based on a pelitic melting model calculated with Perple_X, assuming a granitic composition and is incorporated as a look-up table. We will discuss the numerical implementation, show the results of systematic numerical simulations, and illustrate the effect of volume changes due to crystallization on stresses in the host rocks.</p>

scholarly journals Experimental Results of a Wankel-type Expander Fuelled by Compressed Air and Saturated Steam

2017 ◽  
Vol 105 ◽  
pp. 2929-2934 ◽  
Author(s):  
M. Antonelli ◽  
M. Francesconi ◽  
A. Baccioli ◽  
G. Caposciutti
Keyword(s):  
Experimental Results ◽  
Compressed Air ◽  
Saturated Steam

scholarly journals Emplacement of the Nain anorthosite: diapiric versus conduit ascent

2000 ◽  
Vol 37 (8) ◽  
pp. 1195-1207 ◽  
Author(s):  
K R Royse ◽  
R G Park
Keyword(s):  
Shear Zone ◽  
Host Rock ◽  
Border Zone ◽  
Crystal Mush ◽  
Mafic Rocks ◽  
Outer Border ◽  
Host Rocks ◽  
Nain Plutonic Suite

Estimation of settling velocities of large orthopyroxene megacrysts, found within anorthosite intrusions, are calculated and compared with ascent rates achieved by diapirism and conduit propagation. Calculations suggest that diapirism is far too slow to be an appropriate ascent mechanism for anorthositic crystal mush and favour conduit emplacement. The intrusions of the Nain Plutonic Suite (NPS) are located along the Abloviak shear zone, which marks the boundary between the Nain and Churchill provinces, and within the zone of juxtaposition of the Saglek and Hopedale blocks of the Nain Province. These crustal weaknesses have probably controlled the emplacement and distribution of the intrusions. Contact relations between intrusions of anorthosite and their gneissic host rock provide evidence for two emplacement styles within the NPS, the first typified by strongly deformed and recrystallized rocks, and the second by an outer border zone of mafic rocks. It is proposed that these differences in intrusive style are due to differences in ductility contrast between the magma and its surrounding host rocks, such that those intrusions emplaced into the thermally softened shear zone have deformed margins, whereas those intruded into the cooler Archaean crust have undeformed margins.

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