The volume conjugate in progressive metamorphism

2021 ◽  
Author(s):  
Timothy Chapman ◽  
Geoffrey Clarke ◽  
Luke Milan ◽  
Julie Vry
Keyword(s):  
New Caledonia ◽  
Fluid Pressure ◽  
Crystalline Rocks ◽  
Metamorphic Rocks ◽  
Fluid Consumption ◽  
Volume Changes ◽  
Mineral Equilibria ◽  
Mineral Assemblages ◽  
Physical Changes ◽  
Distribution Of Stresses

<p>Volume changes during metamorphic reactions are key contributors to the physical changes of crystalline rocks. Assessing dehydration or hydration reactions in terms of conjugate <em>V–T</em> pseudosections provides indicators of transient departures in hydrostatic pressure and their impact on observed mineral equilibria. The expansion in volume of major dehydration events such as the breakdown of lawsonite or chlorite delineate zones of fluid overpressure that generate connectivity via fracturing. Net compressional reactions represent sinks for fluid consumption and the focussing of strain. The capacity of metamorphic rocks to generate or consume fluid along portions of the <em>P–T–V</em> path exerts a fundamental control on the distribution of stresses in the crust and the observed mineral assemblages. Coupling a phase equilibria approach to mechanical modelling provides a quantitative framework to assess these changes in fluid pressure that can be compared to prominent case studies in rocks from New Caledonia and New Zealand.</p>

scholarly journals Petrology of the metamorphic rocks (gravels) from Bhajanpur area in Panchagarh District, Bangladesh

1970 ◽  
Vol 5 ◽  
pp. 91-96
Author(s):  
Md Rahat Hossain ◽  
Ismail Hossain ◽  
ASM Zahid Hossain ◽  
Prodip Kumar Biswas
Keyword(s):  
Key Words ◽  
Metamorphic Rock ◽  
Metamorphic Rocks ◽  
Mica Schist ◽  
Mineral Assemblages ◽  
Temperature Ranges ◽  
Garnet Zone ◽  
Opaque Minerals ◽  
Mineralogical Compositions ◽  
Chlorite Schist

The present study deals with petrology of the detrital gravelly rocks from Bhajanpur area, Panchagarh, Bangladesh. The results of detailed petrography of gravelly rocks indicate the presence of quartz (monocrystalline and polycrystalline quartz), K-feldspar, plagioclase, chlorite, muscovite and biotite as major mineralogical compositions. Other minor minerals are garnet, kyanite, graphite and opaque minerals. Based on definitive mineral assemblages, blueschist and greenschist facies sequences are recognized. Correspondingly, index minerals provide chlorite zone, biotite zone, garnet zone, kyanite zone, and graphite zone. The P-T conditions of the studied rocks demonstrate the possible temperature ranges 300-550°C and pressure ranges 2-10 kbar. Most common varieties of metamorphic rocks in the study area are garnet mica schist, chlorite schist, gneiss and few quartzites. Characteristics of garnet mica schist and chlorite schist are equivalent with the lesser Himalayan metamorphic rock sequence in Sikkim area, whereas gneiss from Bhajanpur area has similar precursor as Darjeeling gneiss. Therefore, the sources of detrital metamorphic rocks in Bhajanpur area obviously come from the lesser Himalayan sequence in Sikkim and Darjeeling areas, India. Key words: Petrology; metamorphic rocks; gravels; P-T conditions; Panchagarh; lesser Himalayan sequence DOI: 10.3329/jles.v5i0.7357 J. Life Earth Sci., Vol. 5: 91-96, 2010

Physical and chemical aspects of the development of overpressuring in sedimentary environments

Clay Minerals ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 425-437 ◽  
Author(s):  
P. L. Hall
Keyword(s):  
Fluid Pressure ◽  
Sediment Thickness ◽  
Volume Changes ◽  
Sedimentary Environments ◽  
Vertical Permeability ◽  
Burial Rate ◽  
Long Time ◽  
Physical And Chemical ◽  
First Time ◽  
Applied Stresses

AbstractFluid pressures in argillaceous sediments depend on, inter alia, mechanical stresses, temperature, diagenetic volume changes and permeability. However, the relative influence of the pressuring mechanisms depends critically upon the long time-scale compliance, C, of the overpressured layer.In sediments undergoing first-time burial and currently exposed to their historically maximum applied stresses, C can be relatively large. Here, fluid pressure increases are principally due to mechanical causes, and overpressuring will be associated with undercompaction. The tendency for undercompaction (compaction disequilibrium) depends on the sediment thickness, burial rate and vertical permeability. In other cases, when applied stresses have been reduced by uplift, or when impermeable hard caps or seals have been formed, C may be substantially smaller. Here pore pressures may be predominantly controlled by diagenetic and aquathermal processes, with mechanical (undercompaction) phenomena being relatively less significant.Three-dimensionally sealed overpressured zones may exhibit vertical fluid pressure discontinuities. Within a sealed aquifer, fluid pressures may rise to almost lithostatic values, relieved by episodic fracturing of the seal.

A propos d'un schiste a sillimanite pres de Jerdeux (Hague)

1942 ◽  
Vol S5-XII (1-3) ◽  
pp. 21-24
Author(s):  
Elisabeth Jeremine
Keyword(s):  
Crystalline Rocks ◽  
Metamorphic Rocks ◽  
The Hague

Abstract The pre-Cambrian crystalline rocks of the Hague cape region, northwestern France, although exhibiting only slight variations in character, belong to different metamorphic zones. The sillimanite-bearing schist near Jerdeux, intercalated in an amphibole gneiss which is intruded by granitic injections, belongs to a deeper-seated zone than the metamorphic rocks east of Omonville-la-Rogue.

Abundance of halloysite neoformation in soils developed from crystalline rocks. Contribution of transmission electron microscopy

Clay Minerals ◽  
1992 ◽  
Vol 27 (1) ◽  
pp. 35-46 ◽  
Author(s):  
R. Romero ◽  
M. Robert ◽  
F. Elsass ◽  
C. Garcia
Keyword(s):  
Thermal Analyses ◽  
Crystalline Rocks ◽  
Metamorphic Rocks ◽  
X Ray Diffraction ◽  
Nw Spain ◽  
X Ray ◽  
Transmission Electron ◽  
High Concentrations ◽  
Bioclimatic Conditions ◽  
Mineralogical Phases

AbstractThe soils developed from crystalline and metamorphic rocks in Galicia (NW Spain), are characterized by high concentrations of 1 : 1 phyllosilicates and gels. Thermal analyses, X-ray diffraction after formamide treatment, and IR spectroscopy in the OH vibration range have been performed on the clay fractions, but do not discriminate clearly between the different associated mineralogical phases. HRTEM studies linked with microdiffraction and microanalyses have led to the identification of several types of gel which transform into goethite, gibbsite, clay precursors, and/ or halloysite according to their composition (Fe, Al or Si-Al). Halloysite-like minerals are the main constituents and they have a great variety of morphologies: lamellar, spheroidal, tubular, platy or poikilitic. In general, halloysite and gel formation on crystalline rocks is related to the bioclimatic conditions, involving high hydrolysis in the presence of organic matter. This halloysite seems to be a metastable mineral which would evolve into kaolinite with increasing weathering time.

scholarly journals Whole rock major element influences on monazite growth: examples from igneous and metamorphic rocks in the Menderes Massif, western Turkey

Mineralogia ◽  
2008 ◽  
Vol 39 (1-2) ◽  
pp. 7-30 ◽  
Author(s):  
Elizabeth Catlos ◽  
Courteney Baker ◽  
Ibrahim Çemen ◽  
Cenk Ozerdem
Keyword(s):  
Major Element ◽  
Bulk Composition ◽  
Metamorphic Rocks ◽  
Western Turkey ◽  
Menderes Massif ◽  
Tectonic History ◽  
Major Element Chemistry ◽  
Element Chemistry ◽  
Multi Stage ◽  
Mineral Assemblages

Whole rock major element influences on monazite growth: examples from igneous and metamorphic rocks in the Menderes Massif, western TurkeyMonazite (LREEPO4) is a radiogenic, rare-earth bearing mineral commonly used for geochronology. Here we examine the control of major element chemistry in influencing the crystallization of monazite in granites (Salihli and Turgutlu bodies) and garnet-bearing metamorphic assemblages (Bozdag and Bayindir nappes) from the Menderes Massif, western Turkey. In S-type granites from the massif, the presence of monazite correlates to the CaO and Al2O3content of the whole rock. Granites with monazite only are low Ca (0.6-1.8 wt% CaO). As CaO increases (from 2.1-4.6 wt%), allanite [(Ce, Ca, Y)2(Al, Fe3+)3(SiO4)3(OH)] is present. Higher Al2O3(>15 wt%) rocks contain allanite and/or monazite, whereas those with lower Al2O3contain monazite only. However, examining data reported elsewhere for A-type granites, the correlation between major element chemistry and presence of monazite is likely restricted to S-type lithologies. Pelitic schists of the Menderes Massif show no correlation between major element chemistry and presence of monazite. One Bayindir nappe sample contains both prograde garnets and those affected significantly by diffusion. These rocks have likely experienced a complicated multi-stage tectonic history, which influenced their current mineral assemblages. The presence of monazite in a metamorphic rock can be influenced by the number, duration, and nature of events that were experienced and the degree to which fluids were involved. The source of monazite in the Bayindir and Bozdag samples was likely reactions that involved allanite. These reactions may not have significantly changed the bulk composition of the rock.

A model for the origin of the Lac St. Jean anorthosite massif

1976 ◽  
Vol 13 (2) ◽  
pp. 389-399 ◽  
Author(s):  
R. A. Frith ◽  
K. L. Currie
Keyword(s):  
Experimental Data ◽  
Partial Melting ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Calc Alkaline ◽  
Grenville Province ◽  
Thermal Event ◽  
Anorthosite Massif ◽  
Mineral Assemblages ◽  
Potassic Rocks

An ancient tonalitic complex becomes migmatitic around the Lac St. Jean massif, ultimately losing its identity in the high grade metamorphic rocks surrounding the anorthosite. Field relations suggest extreme metamorphism and anatexis of tonalitic rocks. Experimental data show that extensive partial melting of the tonalite leaves an anorthositic residue. The same process operating on more potassic rocks would leave monzonitic or quartz syenitic residues. Synthesis of experimental data suggests that the process could operate at pressures of 5–8 kbar and temperatures of 800–1000 °C, which are compatible with mineral assemblages around the anorthosite massif. Slightly higher temperatures at the end of the process could generate magmatic anorthosite.Application of the model to the Grenville province as a whole predicts generation of anorthosite during a long-lived thermal event of unusual intensity. Residual anorthosite would occur as a substratum in the crust, overlain by high-grade metamorphic rocks intruded by anorthosite and syenitic rocks, while higher levels in the crust would display abundant calc-alkaline plutons and extrusives.

Potassium-bearing clinopyroxene: a review of experimental, crystal chemical and thermodynamic data with petrological applications

2011 ◽  
Vol 75 (4) ◽  
pp. 2467-2484 ◽  
Author(s):  
O. G. Safonov ◽  
L. Bindi ◽  
V. L. Vinograd
Keyword(s):  
Thermodynamic Data ◽  
Field Model ◽  
Atomistic Simulations ◽  
Standard Enthalpy Of Formation ◽  
Standard Entropy ◽  
Mixing Properties ◽  
Crustal Rocks ◽  
Mineral Equilibria ◽  
Mineral Assemblages ◽  
Experimental Crystal

AbstractAvailable experimental data on chemical composition and crystal structure of K-bearing clinopyroxenes are compiled together with the results of atomistic simulations and thermodynamic calculations of mineral equilibria. It is shown that the limited solubility of K2O in clinopyroxene from crustal rocks cannot be ascribed to the strong non-ideality of mixing between diopside (CaMgSi2O6) and K-jadeite (KAlSi2O6) components. The more likely reason is the instability of the potassic endmember with respect to other K-bearing phases. As the volume effects of typical K-jadeite-forming reactions are negative, the incorporation of K in the clinopyroxene structure becomes less difficult at higher pressure. Atomistic simulations predict that the thermodynamic mixing properties of diopside-K-jadeite solid-solutions at high temperature approach those of a regular mixture with a relatively small positive excess enthalpy. The standard enthalpy of formation (ΔfH° = —2932.7 kJ/mol), the standard volume (V° = 6.479 J mol–1 bar–1) and the isothermal bulk modulus (K0 = 145 GPa) of K-jadeite were calculated from first principles, and the standard entropy (S° = 141.24 J mol–1 K–1) and thermal-expansion coefficient (α = 3.3 x 1CP–5 K–1) of the K-jadeite endmember were estimated using quasi-harmonic lattice-dynamic calculations based on a force-field model. The estimated thermodynamic data are used to compute compositions of K-bearing clinopyroxenes in diverse mineral assemblages within a wide P-T interval. The review substantiates the conclusion that clinopyroxene can serve as an effective container for K at upper-mantle conditions.

40Ar/39Ar dating of white micas from the epidote to the omphacite zones, northern New Caledonia: tectonic implications

1994 ◽  
Vol 31 (6) ◽  
pp. 995-1001 ◽  
Author(s):  
E. D. Ghent ◽  
J. C. Roddick ◽  
P. M. Black
Keyword(s):  
High Pressure ◽  
New Caledonia ◽  
Thermal Modeling ◽  
Closure Temperature ◽  
Metamorphic Rocks ◽  
Areal Extent ◽  
Rock Samples ◽  
Tectonic Implications ◽  
Cooling Unit

An 40Ar/39Ar study of white micas from high-pressure metamorphic rocks of northern New Caledonia yielded cooling ages of 37 ± 1 Ma for both epidote and omphacite zone samples. Whole-rock samples from the lawsonite zone yielded ages in the range 44–51 Ma with complicated age spectra, probably reflecting both detrital and newly grown micas. The areal extent of the mica samples, over 300 km2, suggests that the epidote and omphacite zone rocks cooled through the muscovite closure temperature, about 350 °C, as a coherent cooling unit. Simple thermal modeling suggests that these rocks could have closed at similar times if the unroofing rate were greater than 2–10 mm∙a−1. Lawsonite zone rocks occur structurally within about 0.5 km of garnet–omphacite rocks, suggesting the possibility of major postmetamorphic tectonic displacement.

Alteration, mineralization, and metamorphism in the area of the East South "C" ore zone, 24th level of the Dickenson mine, Red Lake, northwestern Ontario

1984 ◽  
Vol 21 (1) ◽  
pp. 35-52 ◽  
Author(s):  
Neil A. Mathieson ◽  
C. Jay Hodgson
Keyword(s):  
Volcanic Rocks ◽  
Fluid Pressure ◽  
Chemical Effect ◽  
Iron Formation ◽  
Mesoscopic Scale ◽  
Red Lake ◽  
Northwestern Ontario ◽  
Mineral Associations ◽  
Mineral Assemblages ◽  
Volcaniclastic Rocks

The area of the East South "C" (ESC) orebody of the Dickenson mine, Red Lake, consists of variably altered and mineralized basalt, basaltic volcaniclastic rocks, minor sulphidic iron formation, and a series of mainly postdeformation dykes. Except for the dykes, the rocks are in general well foliated. The macroscopic structural geometry of the stratiform rocks has been determined to a large extent by movement on schistosity-parallel faults.Three broad types of mineralization or alteration are recognized: an Na–Ca–Mg depletion with associated Fe–Mn enrichment controlled by primary permeable structures in basalt; a series of carbonate and quartz or "chert" veins emplaced into fissures; and auriferous silicified and sulphidized zones controlled by vein-filled fractures. The last is the main mineralization type in the ESC orebody on the 24th level of the mine, which was the focus of this study. Although all mineralization types occur within the mine, they are not directly associated either temporally or spatially on a mesoscopic scale. All, however, appear to have been overprinted by or formed synchronously with the amphibolite-facies metamorphism.A rich variety of metamorphic mineral assemblages occurs in the volcanic rocks because of the chemical effect of pre- or synmetamorphic hydrothermal alteration. These assemblages and the composition and mineral associations of arsenopyrite in the ESC orebody closely constrain the conditions of metamorphism to 520–540 °C and 3.8–4.2 kbar (380–420 MPa) fluid pressure.

Sign in / Sign up

Export Citation Format

Share Document