Log in

Relevant bibliographies by topics / Porphyroblasts / Journal articles

Journal articles on the topic 'Porphyroblasts'

To see the other types of publications on this topic, follow the link: Porphyroblasts.

Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Porphyroblasts.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Bui, Hau Vinh, Hai Thanh Tran, Thanh Xuan Ngo, and Chi Kim Thi Ngo. "Microstructure characteristics of the ganet-bearing schist from Nam Co formation, Son La area, Song Ma suture zone, Northwestern Vietnam." Journal of Mining and Earth Sciences 62, no. 1 (February 28, 2021): 64–72. http://dx.doi.org/10.46326/jmes.2021.62(1).08.

Full text

Abstract:

The garnet-bearing schists of the Nam Co formation have an identical mineral assemblage consisting of garnet, chlorte, albite, quartz and muscovite, together with accessory apatite, zircon, monazite, xenotime, and ilmenite. An aggregate of muscovite and chlorite defines the major foliations (Sn). Both albite and garnet occur as a porphyroblast, ranging in size 0.2÷1 mm and 0.5÷1.2 mm, respectively. Albite porphyroblasts commonly have the curved to sigmoidal inclusion trails defined by graphitic materials (Sn-1). Garnet porphyroblasts in the sample is generally characterized by paucity of inclusions and retrograde corona of bitotite and chlorite. Garnet also occurs as an inclusion within albite porphyroblast. Porphyroblastic garnet shows the compositional zonation typified by a bell-shaped spessartine profile balanced by increasing almandine from core to rim. Whereas, inclusion garnet is homogeneous compositions with rich in almandin and poor in spessatin, pyrop and grossula. All the above microstructures suggest two deformation and metamorphic stages (M1 and M2) that were affected to politic rocks of the Nam Co formation, Song Ma suture zone.

APA, Harvard, Vancouver, ISO, and other styles

2

Mitchell, J. N. "A Scanning Electron Microscopic study of hematite inclusions in cordierite porphyroblasts." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 680–981. http://dx.doi.org/10.1017/s0424820100144796.

Full text

Abstract:

Porphyroblasts are monocrystalline to polycrystalline mineral grains in metamorphic rocks that are distinctly larger than the matrix grain surrounding them. Their presence reflects the metamorphic release and rapid diffusion of their chemical components, with subsequent crystallization at limited nucleation sites. Small inclusions of other minerals are often present in porphyroblasts, especially in members of the garnet group, staurolite, and cordierite. Various hypotheses may be suggested to explain such inclusions: (1) they are relics of earlier grains, either of the protolith or of a stage of metamorphism prior to porphyroblast growth; (2) they are reaction residues of the mineral grains that decomposed to form the porphyroblasts; or (3) they are decomposition products produced from the porphyroblasts by secondary or retrograde metamorphism.

APA, Harvard, Vancouver, ISO, and other styles

3

Paudel, L. P., T. Imayama, and K. Arita. "Metabasites petrology and P-T evolution in the Lesser Himalaya, central Nepal." Journal of Nepal Geological Society 42 (September 24, 2011): 21–40. http://dx.doi.org/10.3126/jngs.v42i0.31446.

Full text

Abstract:

Petrological study was carried out for the first time on the metabasites of the Lesser Himalaya in central Nepal. The metabasites are mostly tholeiitic basalts emplaced in the elastic sediments as supracrustal dikes and sills, and later metamorphosed together with the host rocks. They contain almost a constant mineral assemblage of Ca-amphiboles + plagioclase + biotite + quartz ± epidote± chlorite + (Fe-Ti oxides). Amphiboles in the form of porphyroblasts show chemical zonation with actinolite/magnesiohomblende cores, tschermakite/ferro-tschermakite rims, and magnesio-hornblende margins. The cores of porphyroblasts are pre-kinematic and were probably formed prior to the Tertiary Himalayan orogeny. The porphyroblast rims and the matrix amphiboles are syn-kinematic and were formed during the Upper Main Central Thrust activity in the Tertiary period. The compositions of both the porphyroblast rims and matrix amphiboles change from actinolite in the chlorite zone to magnesium hornblende in the biotite zone and totschermakite/ferro-tschermakite in the garnet zone. The systematic changes in amphibole compositions as well as petrographic characteristics of metabasites confirm the classical concept of increasing metamorphic grade structurally upwards to the Upper Main Central Thrust in the Lesser Himalaya. Application of hornblende-plagioclase thermobarometry shows a coherent prograde P-T path in zoned amphiboles. The cores of amphibole porphyroblasts were formed at average peak temperature of ~540"C and at pressure of ~3 kbar. The porphyroblast rims and matrix amphiboles were recrystallized at average peak temperatures of ~570°C in the biotite zone and ~630°C in the garnet zone at pressure of ~6 kbar. The metabasites petrology is in favor of the tectono-metamorphic models that relate the inverted metamorphism with thrusting along the Upper Main Central Thrust and coeval inversion of isoiliem1S. It is suggested that published amphibole cooling ages from the Nepalese Lesser Himalaya based on simples, homogeneous mineralogy should be reinterpreted in view of the presence of polygenetic amphiboles with heterogeneous composition.

APA, Harvard, Vancouver, ISO, and other styles

4

Shchepetova, O. V., A. V. Korsakova, P. S. Zelenovskiy, and D. S. Mikhailenko. "The mechanism of disordered graphite formation in uph diamond-bearing complexes." Доклады Академии наук 484, no. 2 (April 13, 2019): 215–19. http://dx.doi.org/10.31857/s0869-56524842215-219.

Full text

Abstract:

Kyanite gneiss from the "New Barchinsky" locality (Kokchetav Massif) was studied in detail. This rock is characterized by zonal distribution of the C and SiO2 polymorphs in kyanite porphyroblasts: (1) porphyroblast cores with graphite and quartz inclusions; (2) clean overgrowth zone with inclusions of cuboctahedral diamond crystals. The Raman mapping of SiO2 polymorphs originally showed the presence of an association of disordered graphite + coesite “prohibited” in HT diamond-bearing rocks. Graphitization of diamond is the only likely mechanism of the disordered graphite formation in HT diamond-bearing rocks. However, the absence of disordered graphite in association with diamond in kyanite porphyroblasts from kyanite gneiss from the "New Barchinsky" locality eliminates the process of diamond graphitization at the retrograde stage. Most likely, crystallization of disordered graphite occurred at the retrograde stage from the UHP C-O-H fluid.

APA, Harvard, Vancouver, ISO, and other styles

5

Davis, B. K. "Biotite porphyroblast nucleation and growth: control by microfracture of pre-existing foliations in schists in the Robertson River Metamorphics, Australia." Geological Magazine 133, no. 1 (January 1996): 91–102. http://dx.doi.org/10.1017/s0016756800007275.

Full text

Abstract:

AbstractA macroscopic fold formed during the fourth deformation, D4, in the Robertson River Metamorphics, north Queensland, Australia. Growth of biotite, garnet, staurolite and andalusite porphyroblasts also occurred synchronous with D4. Only biotite porphyroblasts have formed preferred alignments across the fold, and they define two dominant orientations. The more common is parallel to D4 fold axes, which is also parallel to D1 D2 and D4 intersection lineations. The other varies up to 90° from this within the D4 axial plane. Mineral elongation lineations do not reflect the extension direction of the deformation in which they formed (D4), but are a function of pre-existing anisotropics in the rock parallel to intersection lin-eations. Porphyroblast growth is inferred to be a result of microfracturing along favourably oriented linear anisotropics formed by multiple intersection of foliations, as well as parting of the the S1, and S2 foliations.

APA, Harvard, Vancouver, ISO, and other styles

6

Rice, A. H. N., and J. I. Mitchell. "Porphyroblast textural sector-zoning and matrix displacement." Mineralogical Magazine 55, no. 380 (September 1991): 379–96. http://dx.doi.org/10.1180/minmag.1991.055.380.08.

Full text

Abstract:

AbstractThere is an association between the development of cleavage domes, a texture reflecting the displacement of insoluble matrix grains by porphyroblasts growing under a bulk hydrostatic stress, and textural sector-zoning. This has been found in garnet, staurolite, chiastolite, pyrite and possibly emerald porphyroblasts. Sector-zoned porphyroblasts form by lineage growth normal to the crystal faces. This causes several distinctive textures (type 1 inclusions and type 2 intergrowths, inclusion bands, growth prongs), all of which are directly or indirectly related to displacement growth. Graphite or other carbonaceous material is ubiquitous in samples showing textural sector-zoning.

APA, Harvard, Vancouver, ISO, and other styles

7

Carlson, William D. "Competitive diffusion-controlled growth of porphyroblasts." Mineralogical Magazine 55, no. 380 (September 1991): 317–30. http://dx.doi.org/10.1180/minmag.1991.055.380.03.

Full text

Abstract:

AbstractIn a diffusion-controlled process of nucleation and growth, adjacent porphyroblasts compete with one another for nutrients. When the effects of this competition are evaluated quantitatively for garnet porphyroblasts in pelitic rocks from the Picuris Range of New Mexico (U.S.A.), significant correlations arise between crystal sizes and the volumes of the domains from which the crystals drew their nutrients. These correlations strengthen the conclusion drawn from earlier work on spatial dispositions, zoning patterns, and crystal size distributions that the kinetics of intergranular diffusion governed the crystallisation of these porphyroblasts.Computer simulations indicate that competition for nutrients during diffusion-controlled growth may have small but detectable effects on crystal size frequency distributions. Diffusional competition therefore introduces relatively minor inaccuracies into attempts to extract quantitative information on crystallisation processes from size distributions using models for the growth of isolated porphyroblasts. In contrast, the effects of diffusional competition on patterns of compositional zoning may be substantial, especially for porphyroblasts in rocks for which chemical inhomogeneity of the precursor leads to strongly clustered spatial dispositions. In such rocks, clustering may alter the patterns of compositional zoning in ways that obscure evidence for diffusion-controlled growth.

APA, Harvard, Vancouver, ISO, and other styles

8

Pan, Yuanming, Michael E. Fleet, and Neil D. Macrae. "Oriented monazite inclusions in apatite porphyroblasts from the Hemlo gold deposit, Ontario, Canada." Mineralogical Magazine 57, no. 389 (December 1993): 697–707. http://dx.doi.org/10.1180/minmag.1993.057.389.14.

Full text

Abstract:

AbstractOriented inclusions of monazite occur in the dark core of apatite porphyroblasts in a muscovite schist from the Archaean Hemlo gold deposit, Ontario, Canada. The monazite inclusions are elongated along the b-axis and parallel to the c-axis of the apatite host; the complete orientation relationship of the monazite/apatite intergrowth is bMnz//cAp, cMnz//aAp. From analysis by SIMS and EMP, the dark core of the apatite porphyroblasts is depleted in LREE (LaN/YbN = 0.56). The monazite inclusions are correspondingly enriched in LREE, but markedly depleted in HREE, compared with monazite grains in the rock matrix and cross-cutting veins. The monazite inclusions precipitated by oriented reaction through rock-fluid interactions during a late hydrothermal alteration. Their unusual REE composition is probably related to both a preferential leaching of LREE from the dark core and a selective transfer of HREE out of the apatite porphyroblasts.

APA, Harvard, Vancouver, ISO, and other styles

9

Redlińska-Marczyńska, Aleksandra. "Gierałtów versus Śnieżnik gneisses - what is the real difference?" Geologos 17, no. 2 (June 1, 2011): 71–96. http://dx.doi.org/10.2478/v10118-011-0005-6.

Full text

Abstract:

Gierałtów versus Śnieżnik gneisses - what is the real difference?Structural and petrographic study applied to the gneisses from the eastern part of the Orlica-Śnieżnik Dome, indicate that two different types of gneiss are present. The Śnieżnik gneisses are porphyrithic granites, constricted and sheared into L-S tectonites, most commonly with augens; the Gierałtów gneisses are sheared migmatites, porphyroblastic gneisses and banded gneisses, with two sets of metamorphic foliation, intrafolial folds and lensoid leucosome aggregates or metamorphic porphyroblasts. Both lithologies were later zonally sheared and transformed into more or less deformationally advanced mylonites, difficult to be distinguished from one of the two types. Identification of the Śnieżnik and Gierałtów gneisses is possible only between zones of the late (Variscan) shearing, in which the original, pre-kinematic structures are preserved.

APA, Harvard, Vancouver, ISO, and other styles

10

Hirajima, T., R. Zhang, J. Li, and B. Cong. "Petrology of the nyböite-bearing eclogite in the Donghai area, Jiangsu Province, eastern China." Mineralogical Magazine 56, no. 382 (March 1992): 37–46. http://dx.doi.org/10.1180/minmag.1992.056.382.05.

Full text

Abstract:

AbstractNyböite occurs as porphyroblasts in the Jianchang eclogite in the Donghai area, northeastern Jiangsu Province, eastern China. The Jianchang eclogite contains some inclusions of quartz after coesite in clinopyroxene, garnet and epidote. It has colourless to pale-violet pleochroism. A thin rim with violet pleochroism often develops around nyb6ite and is taramitic. It is further retrogressed by the symplectite which is mainly composed of hornblende, aegirine-augite and albite. Nyböite is associated with jadeitic pyroxene in the Jianchang eclogite, although other porphyroblastic amphiboles in other Donghai eclogites are barroisitic to katophoritic and are associated with omphacite.Fe-Mg partitioning between garnet and clinopyroxene and the presence of coesite pseudomorphs indicate P-T conditions in the Jianchang eclogite of about 740 ± 60°C and more than 28 kbar. Similar P-T conditions were estimated for other porphyroblastic amphibole-bearing eclogites in the Donghai area. Nyböite can occur in the Na-Al-Fe-rich local bulk composition under the medium to high temperature and very high-pressure conditions. Retrograde rim amphibole is poorer in NaB, variable in Si content, and richer in NaA variable than the porphyroblastic amphibole in the Donghai area. This roughly implies a P-T path where P decreases without a large decrease of T.

APA, Harvard, Vancouver, ISO, and other styles

11

Tiwary, Anju, Mihir Deb, and Nigel J. Cook. "Use of pyrite microfabric as a key to tectono-thermal evolution of massive sulphide deposits – an example from Deri, southern Rajasthan, India." Mineralogical Magazine 62, no. 2 (April 1998): 197–212. http://dx.doi.org/10.1180/002646198547576.

Full text

Abstract:

AbstractPyrite is an ubiquitous constituent of the Proterozoic massive sulphide deposit at Deri, in the South Delhi Fold Belt of southern Rajasthan. Preserved pyrite microfabrics in the Zn-Pb-Cu sulphide ores of Deri reveal a polyphase growth history of the iron sulphide and enable the tectono-thermal evolution of the deposit to be reconstructed.Primary sedimentary features in Deri pyrites are preserved as compositional banding. Regional metamorphism from mid-greenschist to low amphibolite facies is recorded by various microtextures of pyrite. Trails of fine grained pyrite inclusions within hornblende porphyroblasts define S1-schistosity. Pyrite boudins aligned parallel to S1 mark the brittle–ductile transformation of pyrite during the earliest deformation in the region. Isoclinal to tight folds (F1 and F2) in pyrite layers relate to a ductile deformation stage during progressive regional metamorphism. Peak metamorphic conditions around 550°C, an estimation supported by garnet–biotite thermometry, resulted in annealing of pyrite grains, while porphyroblastic growth of pyrite (up to 900 µm) took place along the retrogressive path. Brittle deformation of pyrite and growth of irregular pyritic mass around such fractured porphyroblasts characterize the waning phase of regional metamorphism. A subsequent phase of stress-free, thermal metamorphism is recorded in the decussate and rosette textures of arsenopyrite prisms replacing irregular pyritic mass. Annealing of such patchy pyrite provides information regarding the temperature conditions during this episode of thermal metamorphism which is consistent with the hornblendehornfels facies metamorphism interpreted from magnetite–ilmenite geothermometry (550°C) and sphalerite geobarometry (3.5 kbar). A mild cataclastic deformation during the penultimate phase produced microfaults in twinned arsenopyrite prisms.

APA, Harvard, Vancouver, ISO, and other styles

12

Jiang, Dazhi. "Reading history of folding from porphyroblasts." Journal of Structural Geology 23, no. 9 (September 2001): 1327–35. http://dx.doi.org/10.1016/s0191-8141(01)00013-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Franceschelli, M., and I. Memmi. "Zoning of chloritoid from kyanite-facies metapsammites, Alpi Apuane, Italy." Mineralogical Magazine 63, no. 1 (February 1999): 105–10. http://dx.doi.org/10.1180/002646199548222.

Full text

Abstract:

AbstractChloritoid with significant Mg-Fe zoning occurs as lath-shaped porphyroblasts and as clusters of subradiating crystals in the Triassic Verrucano metapsammite (quartz + muscovite + chlorite + chloritoid ± kyanite) of the Massa Unit, Alpi Apuane. Two main types of chloritoid zoning profiles were found. The first type is characterised by gradual increase in Mg from core to rim of the porphyroblasts. In the second type the Mg content is constant from the core to the inner rim, but sharply decreases in the outer rim. Both types of zoning have been interpreted as the result of prograde growth during the Alpine metamorphism. The temperature, estimated using the chlorite-chloritoid thermometer, ranges from 467 to 560°C.

APA, Harvard, Vancouver, ISO, and other styles

14

Ilnicki, S. "Variscan progradeP-Tevolution and contact metamorphism in metabasites from the Sowia Dolina, Karkonosze-Izera massif, SW Poland." Mineralogical Magazine 75, no. 1 (February 2011): 185–212. http://dx.doi.org/10.1180/minmag.2011.075.1.185.

Full text

Abstract:

AbstractSeveral bodies of moderately foliated and porphyroblastic metabasites crop out on the SE side of the metamorphic cover of the Karkonosze granite within metapelites of the Sowia Dolina area (West Sudetes, Saxothuringian zone). Depending on the microstructural setting of the Ca-amphiboles in the rocks, different mineral-chemical trends have been determined for Si,XMg, AlVI,A[Na+K] which serve as semi-quantitative indicators of temperature and pressure changes. Porphyroblasts and prisms oblique to the main foliation in schistose metabasites show zoning from Mg-hornblende and actinolite to tschermakite, and then to Mg-hornblende (or actinolite). Matrix amphiboles and those in pressure shadows around some porphyroblasts have tschermakitic cores and actinolitic rims. Rarely, Ca-amphibole is accompanied in schists by late- to post-tectonic cummingtonite. Thermobarometric calculations involving empirically calibrated amphibole equilibria enable a reconstruction ofP-Tpaths for individual rocks and the unravelling of the metamorphic evolution of the metabasites. Peak metamorphic temperatures of 615–640°C and pressures of 7.3–8.2 kbar were preceded by a variably preserved earlier stage (T = 370–550°C, P = 2.8–6.2 kbar). The final metamorphic episode took place at 450–550°C and 2.5–4.8 kbar and is recorded particularly in rocks close to the Karkonosze pluton. The metabasites shed new light on the history of metamorphism in the Sowia Dolina area. The first two stages ofMP-MTmetamorphism, coeval with Variscan deformation events (continental collision, burial and subsequent exhumation), took place under epidote-amphibolite then amphibolite facies conditions. The last stage partly concurred with the final stages of Variscan deformation and overlapped the onset of thermal activity associated with the Karkonosze granite. This metamorphic event is documented by metabasites (occasionally cummingtonite-bearing) outcropping close to the granite. Finally, a prehnitebearing assemblage reflects retrograde re-equilibration under greenschist/sub-greenschist facies conditions (T<300–350°C,P<2.5–3 kbar), which might also be partly due to hydrothermal activity around the pluton.

APA, Harvard, Vancouver, ISO, and other styles

15

Miyazaki, K. "THE CASE AGAINST OSTWALD RIPENING OF PORPHYROBLASTS: DISCUSSION." Canadian Mineralogist 38, no. 4 (August 1, 2000): 1027–28. http://dx.doi.org/10.2113/gscanmin.38.4.1027.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Carlson, W. D. "THE CASE AGAINST OSTWALD RIPENING OF PORPHYROBLASTS: REPLY." Canadian Mineralogist 38, no. 4 (August 1, 2000): 1029–31. http://dx.doi.org/10.2113/gscanmin.38.4.1029.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Vernon, R. H. "K-feldspar megacrysts in granites — Phenocrysts, not porphyroblasts." Earth-Science Reviews 23, no. 1 (February 1986): 1–63. http://dx.doi.org/10.1016/0012-8252(86)90003-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Braga, R., H. J. Massonne, and L. Morten. "An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite." Mineralogical Magazine 71, no. 06 (December 2007): 691–702. http://dx.doi.org/10.1180/minmag.2007.071.6.691.

Full text

Abstract:

Abstract The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution of these relics to the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11–12 kbar and 600–650°C followed by decompressional heating to 720°C and 9–10 kbar and final cooling at 7 kbar, 550–600°C. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330–340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.

APA, Harvard, Vancouver, ISO, and other styles

19

Kumar Samanta, Susanta, Nibir Mandal, Chandan Chakraborty, and Koushik Majumder. "Simulation of inclusion trail patterns within rotating synkinematic porphyroblasts." Computers & Geosciences 28, no. 3 (April 2002): 297–308. http://dx.doi.org/10.1016/s0098-3004(01)00013-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Beam, Eric C., and Donald M. Fisher. "An estimate of kinematic vorticity from rotated elongate porphyroblasts." Journal of Structural Geology 21, no. 11 (November 1999): 1553–59. http://dx.doi.org/10.1016/s0191-8141(99)00110-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Liu, Wenlong, Yi Cao, Junfeng Zhang, Yanfei Zhang, Keqing Zong, and Zhenmin Jin. "Thermo-Structural Evolution of the Val Malenco (Italy) Peridotite: A Petrological, Geochemical and Microstructural Study." Minerals 10, no. 11 (October 28, 2020): 962. http://dx.doi.org/10.3390/min10110962.

Full text

Abstract:

The Val Malenco peridotite massif is one of the largest exposed ultramafic massifs in Alpine orogen. To better constrain its tectonic history, we have performed a comprehensive petro-structural and geochemical study. Our results show that the Val Malenco serpentinized peridotite recorded both pre-Alpine extension and Alpine convergence events. The pre-Alpine extension is recorded by microstructural and geochemical features preserved in clinopyroxene and olivine porphyroblasts, including partial melting and refertilisation, high-temperature (900–1000 °C) deformation and a cooling, and fluid-rock reaction. The following Alpine convergence in a supra-subduction zone setting is documented by subduction-related prograde metamorphism features preserved in the coarse-grained antigorite and olivine grains in the less-strained olivine-rich layers, and later low-temperature (<350 °C) serpentinization in the fine-grained antigorite in the more strained antigorite-rich layers. The strain shadow structure in the more strained antigorite-rich layer composed of dissolving clinopyroxene porphyroblast and the precipitated oriented diopside and olivine suggest dissolution and precipitation creep, while the consistency between the strain shadow structure and alternating less- and more-strained serpentinized domains highlights the increasing role of strain localization induced by the dissolution-precipitation creep with decreasing temperature during exhumation in Alpine convergence events.

APA, Harvard, Vancouver, ISO, and other styles

22

Dempster, Tim J., Sarah Coleman, Ross Kennedy, Peter Chung, and Roderick W. Brown. "Growth zoning of garnet porphyroblasts: Grain boundary and microtopographic controls." Journal of Metamorphic Geology 38, no. 9 (August 30, 2020): 1011–27. http://dx.doi.org/10.1111/jmg.12558.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

VERNON, R. H. "Microstructural evidence of rotation and non-rotation of mica porphyroblasts." Journal of Metamorphic Geology 6, no. 5 (September 1988): 595–601. http://dx.doi.org/10.1111/j.1525-1314.1988.tb00442.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

HIRSCH, D. M., and W. D. CARLSON. "Variations in rates of nucleation and growth of biotite porphyroblasts." Journal of Metamorphic Geology 24, no. 8 (October 2006): 763–77. http://dx.doi.org/10.1111/j.1525-1314.2006.00667.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

KETCHAM, R. A., and W. D. CARLSON. "Numerical simulation of diffusion-controlled nucleation and growth of porphyroblasts." Journal of Metamorphic Geology 30, no. 5 (May 9, 2012): 489–512. http://dx.doi.org/10.1111/j.1525-1314.2012.00978.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Macheva, Lyubomira. "Preliminary data for melt inclusions in garnet porphyroblasts from Ograzhden metapelites, SW Bulgaria." Review of the Bulgarian Geological Society 81, no. 3 (December 2020): 84–86. http://dx.doi.org/10.52215/rev.bgs.2020.81.3.84.

Full text

Abstract:

Micro-inclusions in garnet porphyroblasts from high-grade Ograzhden metapelites, SW Bulgaria, have been studied by SEM and micro-Raman Spectroscopy. Micro-inclusions are presented by single grains with facetted outlines parallel to rational crystallographic orientations of the host garnet or by multiphase aggregates with negative crystal shape. Many of studied micro-inclusions can be formed by the presence of melt. The morphology of some of them suggests formation under high pressure metamorphism.

APA, Harvard, Vancouver, ISO, and other styles

27

Vaskovic, Nada. "Petrology and P-T condition of white mica-chlorite schists from Vlasina series - Surdulica, SE Serbia." Annales g?ologiques de la Peninsule balkanique, no. 64 (2002): 199–220. http://dx.doi.org/10.2298/gabp0264199v.

Full text

Abstract:

This paper reports structural, textural, petrological and metamorphic data from Vlasina Series of greenschists rocks (as part of the Upper Complex of the Serbo-Macedonian Massif) within which group of white mica-chlorite schist are extensively developed. This group of rocks made the ground of series in which various types of green rocks appear as a lenses and small irregular mass, rarely as dykes. Other features, that characterize these rocks, are the common occurrence of albite and garnet (subordinate) porphyroblasts, as well as development of quartz segregation. Group of white mica-chlorite schist makes about 75 vol. % of Series. Among them, according to mode and mineral composition, the following schist varieties are distinguished: albite-white mica-chlorite (?garnet), white mica-chlorite (?garnet), albite-white mica, sericite-chlorite (?albite), graphite-sericite as well as phyllites and calcshists. Their metamorphic evolution is characterized by the development of a metamorphic episode during Carboniferous - c. 350-330 Ma (Milovanovic et al., 1988) of low to medium P and T. The mineral assemblages of first phase (low PT) is preserved as a very thin Si=S1 foliation included in albite porphyroblast or as small polygonal arcs of S1 in S2 foliation. Textural, mineralogical and petrological data indicate that original volcanoclastic-sedimentary series was transformed during three phase of deformation and metamorphism in the temperature range from 320-415?C, locally 450-500?C and pressures 3 to 5 kbar.

APA, Harvard, Vancouver, ISO, and other styles

28

BUSA, M. D., and N. H. GRAY. "Rotated staurolite porphyroblasts in the Littleton Schist at Bolton, Connecticut, USA." Journal of Metamorphic Geology 10, no. 5 (September 1992): 627–36. http://dx.doi.org/10.1111/j.1525-1314.1992.tb00111.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

BJØRNERUD, M. G., and HUBAO ZHANG. "Rotation of porphyroblasts in non-coaxial deformation: insights from computer simulations." Journal of Metamorphic Geology 12, no. 2 (March 1994): 135–39. http://dx.doi.org/10.1111/j.1525-1314.1994.tb00009.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Hall, A. J., A. J. Boyce, and A. E. Fallick. "A Sulphur Isotope Study of Iron Sulphides in the Late Precambrian Dalradian Easdale Slate Formation, Argyll, Scotland." Mineralogical Magazine 52, no. 367 (September 1988): 483–90. http://dx.doi.org/10.1180/minmag.1988.052.367.06.

Full text

Abstract:

AbstractPyritic slates from the late Precambrian, Middle Dalradian Argyll Group Easdale Slate Formation, contain mainly quartz, muscovite and chlorite with variable amounts of dolomite, albite and paragonite. Slates from Easdale Island and Cuan Ferry contain pyrite porphyroblasts with δ34S = + 12 to + 16‰. The pyrite grew during a post-tectonic retrogressive event at the expense ofpyrrhotine which formed during the main regional metamorphism of the Grampian orogeny by reduction of diagenetic pyrite. Slate from Oban contains abundant diagenetic framboidal pyrite and small syn-tectonic pyrite porphyroblasts with δ34S = +22‰. This pyrite was not all reduced to pyrrhotine on metamorphism so there was little retrogressive growth of pyrite. Metamorphism appears to have homogenized local (cm scale at least) isotopic inhomogeneities and preserved an average seawater-sulphate-sulphide isotopic fractionation value. Middle Dalradian seawater-sulphate had a δ34S value of about + 35‰, so the small fractionations are appropriate for bacteriogenic reduction in bituminous sediments, the heavier sulphide in the case of the Oban slate indicating more rapid reduction of sulphate. Lower Dalradian Appin Group, Ballachulish slate contains pyrite with δ34S = +15±2‰ and is best interpreted as forming in the same manner as the Easdale slates of Easdale Island and Cuan Ferry; the sharp increase in late Precambrian ocean-sulphate sulphur isotope signature from +15 to > +30‰ therefore occurred by Lower Dalradian Appin Group times.

APA, Harvard, Vancouver, ISO, and other styles

31

Moore, Stephanie J., and William D. Carlson. "Evaluation of a combined HRXCT/EBSD method for detecting epitaxial nucleation of garnet porphyroblasts." European Journal of Mineralogy 27, no. 1 (February 18, 2015): 19–29. http://dx.doi.org/10.1127/ejm/2014/0026-2415.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Aerden, Domingo G. A. M., Alejandro Ruiz-Fuentes, Mohammad Sayab, and Aidan Forde. "Kinematics of subduction in the Ibero-Armorican arc constrained by 3D microstructural analysis of garnet and pseudomorphed lawsonite porphyroblasts from Île de Groix (Variscan belt)." Solid Earth 12, no. 4 (April 26, 2021): 971–92. http://dx.doi.org/10.5194/se-12-971-2021.

Full text

Abstract:

Abstract. The small island of Groix in southern Brittany, France, is well known for exceptionally well-preserved outcrops of Variscan blueschists, eclogites, and garnetiferous mica schists that mark a Late Devonian suture between Gondwana and Armorica. The kinematics of polyphase deformation in these rocks is reconstructed based on 3D microstructural analysis of inclusion trails within garnet and pseudomorphed lawsonite porphyroblasts using differently oriented thin sections and X-ray tomography. Three sets of inclusion trails striking NE–SW, NNW–SSE, and WNW–ESE are recognized and interpreted to witness a succession of different crustal shortening directions orthogonal to these strikes. The curvature sense of sigmoidal and spiral-shaped inclusion trails of the youngest set is shown to be consistent with northwest and northward subduction of Gondwana under Armorica, provided that these microstructures developed by overgrowth of actively forming crenulations without much porphyroblast rotation. Strongly non-cylindrical folds locally found on the island are reinterpreted as fold-interference structures instead of having formed by progressive shearing and fold-axis reorientation. Six samples of a lower-grade footwall unit of the Groix ophiolitic nappe (Pouldu schists) were also studied. Inclusion trails in these rocks strike E–W, similar to the youngest set recognized on Groix island. They record Carboniferous N–S shortening during continental collision. These new microstructural data from southern Brittany bear a strong resemblance to earlier measured in inclusion-trail orientations in the northwestern Iberia Massif. A best fit between both regions suggests not more than about 15∘ anticlockwise rotation of Iberia during the Cretaceous opening of the Gulf of Biscay.

APA, Harvard, Vancouver, ISO, and other styles

33

Vernon, R. H. "K-feldspar augen in felsic gneisses and mylonites—deformed phenocrysts or porphyroblasts?" Geologiska Föreningen i Stockholm Förhandlingar 112, no. 2 (June 1990): 157–67. http://dx.doi.org/10.1080/11035899009453175.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Guiping, ZHAO, LIU Shuwen, and LIU Xiaohan. "Compositional Distribution and Growth Mode of Garnet Porphyroblasts during Deformation and Metamorphism." Acta Geologica Sinica - English Edition 78, no. 1 (September 7, 2010): 186–90. http://dx.doi.org/10.1111/j.1755-6724.2004.tb00691.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

JAMIESON, R. A., and A. M. O'BEIRNE-RYAN. "Decompression-induced growth of albite porphyroblasts, Fleur de Lys Supergroup, western Newfoundland." Journal of Metamorphic Geology 9, no. 4 (July 1991): 433–39. http://dx.doi.org/10.1111/j.1525-1314.1991.tb00537.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Bestel, Martina, Timo Gawronski, Rainer Abart, and Dieter Rhede. "Compositional zoning of garnet porphyroblasts from the polymetamorphic Wölz Complex, Eastern Alps." Mineralogy and Petrology 97, no. 3-4 (October 21, 2009): 173–88. http://dx.doi.org/10.1007/s00710-009-0084-z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Tursi, Fabrizio. "The key role of µH2O gradients in deciphering microstructures and mineral assemblages of mylonites: examples from the Calabria polymetamorphic terrane." Mineralogy and Petrology 116, no. 1 (October 20, 2021): 1–14. http://dx.doi.org/10.1007/s00710-021-00766-8.

Full text

Abstract:

AbstractA careful petrologic analysis of mylonites’ mineral assemblages is crucial for a thorough comprehension of the rheologic behaviour of ductile shear zones active during an orogenesis. In this view, understanding the way new minerals form in rocks sheared in a ductile manner and why relict porphyroblasts are preserved in zones where mineral reactions are generally supposed to be deformation-assisted, is essential. To this goal, the role of chemical potential gradients, particularly that of H2O (µH2O), was examined here through phase equilibrium modelling of syn-kinematic mineral assemblages developed in three distinct mylonites from the Calabria polymetamorphic terrane. Results revealed that gradients in chemical potentials have effects on the mineral assemblages of the studied mylonites, and that new syn-kinematic minerals formed in higher-µH2O conditions than the surroundings. In each case study, the banded fabric of the mylonites is related to the fluid availability in the system, with the fluid that was internally generated by the breakdown of OH-bearing minerals. The gradients in µH2O favoured the origin of bands enriched in hydrated minerals alternated with bands where anhydrous minerals were preserved even during exhumation. Thermodynamic modelling highlights that during the prograde stage of metamorphism, high-µH2O was necessary to form new minerals while relict, anhydrous porphyroblasts remained stable in condition of low-µH2O even during exhumation. Hence, the approach used in this contribution is an in-depth investigation of the fluid-present/-deficient conditions that affected mylonites during their activity, and provides a more robust interpretation of their microstructures, finally helping to explain the rheologic behaviour of ductile shear zones.

APA, Harvard, Vancouver, ISO, and other styles

38

Spiess, R., L. Peruzzo, D. J. Prior, and J. Wheeler. "Development of garnet porphyroblasts by multiple nucleation, coalescence and boundary misorientation-driven rotations." Journal of Metamorphic Geology 19, no. 3 (May 2001): 269–90. http://dx.doi.org/10.1046/j.1525-1314.2001.00311.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Spiess, R., L. Peruzzo, D. J. Prior, and J. Wheeler. "Development of garnet porphyroblasts by multiple nucleation, coalescence and boundary misorientation-driven rotations." Journal of Metamorphic Geology 19, no. 3 (May 2001): 269. http://dx.doi.org/10.1046/j.0263-4929.2000.00311.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Pollington, Anthony D., and Ethan F. Baxter. "High precision microsampling and preparation of zoned garnet porphyroblasts for Sm–Nd geochronology." Chemical Geology 281, no. 3-4 (February 2011): 270–82. http://dx.doi.org/10.1016/j.chemgeo.2010.12.014.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Visser, Peter, and Neil S. Mancktelow. "The rotation of garnet porphyroblasts around a single fold, Lukmanier Pass, Central Alps." Journal of Structural Geology 14, no. 10 (November 1992): 1193–202. http://dx.doi.org/10.1016/0191-8141(92)90069-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Miyake, Akira. "Rotation of biotite porphyroblasts in pelitic schist from the Nukata area, central Japan." Journal of Structural Geology 15, no. 11 (November 1993): 1303–13. http://dx.doi.org/10.1016/0191-8141(93)90104-i.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Pan, Yuanming, and Michael E. Fleet. "Polymetamorphism in the Archean Hemlo – Heron Bay greenstone belt, Superior Province: P–T variations and implications for tectonic evolution." Canadian Journal of Earth Sciences 30, no. 5 (May 1, 1993): 985–96. http://dx.doi.org/10.1139/e93-082.

Full text

Abstract:

The tectono-metamorphic history of the late Archean (2800–2600 Ma) Hemlo – Heron Bay greenstone belt in the Superior Province has been delineated from textural relationships, mineral chemistry, and P–T paths in metapelites, cordierite–orthoamphibole rocks, and metabasites from the White River exploration property, Hemlo area, Ontario. An early low-temperature, medium-pressure metamorphism (about 500 °C and 6–6.5 kbar (1 kbar = 100 MPa)) is indicated by the occurrence of relict kyanite and staurolite porphyroblasts and zoned garnet porphyroblasts in metapelites and the presence of zoned calcic amphiboles in metabasites. This early metamorphism appears to have been coeval with the previously documented D1 deformation that is associated with, for example, low-angle thrusts. A second regional metamorphism predominates in the Hemlo – Heron Bay greenstone belt and is generally of relatively low grade, at about 510–530 °C and 3.2–3.5 kbar, over most of the study area and increases to medium grade (550–650 °C and 4–5 kbar) towards the southern margin with the Pukaskwa Gneissic Complex and along the central axis enclosing the Hemlo Shear Zone. The second regional metamorphism was contemporaneous with the D3 deformation and was probably related to plutonism. This type of polymetamorphism in the Hemlo – Heron Bay greenstone belt may be equivalent to those in Phanerozoic subduction complexes and therefore supports the arc–arc accretion model for the development of the southern Superior Province. Although the Hemlo – Heron Bay greenstone belt most likely represents a single tectonic environment (an oceanic island arc), the restricted occurrence of the relict kyanite and staurolite indicates that the central portion of this Archean greenstone belt probably was at a deeper crustal level at the time of the first metamorphic event.

APA, Harvard, Vancouver, ISO, and other styles

44

BELL, T. H., K. A. HICKEY, and J. WANG. "Spiral and staircase inclusion trail axes within garnet and staurolite porphyroblasts from schists of the Bolton Syncline, Connecticut: timing of porphyroblast growth and the effects of fold development." Journal of Metamorphic Geology 15, no. 4 (July 1997): 467–78. http://dx.doi.org/10.1111/j.1525-1314.1997.00032.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Jeong, G. Y., and Y. H. Kim. "Goldmanite from the black slates of the Ogcheon belt, Korea." Mineralogical Magazine 63, no. 2 (April 1999): 253–56. http://dx.doi.org/10.1180/002646199548358.

Full text

Abstract:

AbstractGoldmanite, the vanadium analogue of grossular and andradite, was found as subrounded green porphyroblasts ranging from 0.1 to 1.7 mm in size in the carbonaceous black slates from the Deokpyeong area of the Ogcheon belt in Korea. A radiating aggregate of slightly curved blades of goldmanite crystals displays birefringence and replaces the fine-grained black matrix. The V2O3 content ranges from 21.9 to 26.6 wt.% (24.0 wt.% average), higher than previously reported values. The calculated mole % of the goldmanite end-member ranges from 72 to 91. Its cell dimension was calculated to be 12.04 Å from X-ray diffraction. The black slate in the Deokpyeong area is the richest known accessible source of relatively pure goldmanite.

APA, Harvard, Vancouver, ISO, and other styles

46

Yeh, Meng-Wan. "The Significance and Application of Foliation Intersection/Inflection Axes (FIA( within Porphyroblasts: A review." Terrestrial, Atmospheric and Oceanic Sciences 14, no. 4 (2003): 401. http://dx.doi.org/10.3319/tao.2003.14.4.401(t).

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Kraus, Jürgen, and Paul F. Williams. "A new spin on ‘non-rotating’ porphyroblasts: implications of cleavage refraction and reference frames." Journal of Structural Geology 23, no. 6-7 (June 2001): 963–71. http://dx.doi.org/10.1016/s0191-8141(00)00167-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Aerden, Domingo G. A. M. "Correlating deformation in Variscan NW-Iberia using porphyroblasts; implications for the Ibero-Armorican Arc." Journal of Structural Geology 26, no. 1 (January 2004): 177–96. http://dx.doi.org/10.1016/s0191-8141(03)00070-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Kim, Hyeong Soo, and Ioan V. Sanislav. "Foliation intersection/inflection axes within porphyroblasts (FIAs): a review of advanced applications and significance." Geosciences Journal 21, no. 6 (December 2017): 1013–32. http://dx.doi.org/10.1007/s12303-017-0047-z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Aerden, Domingo, and Mohammad Sayab. "From Adria- to Africa-driven orogenesis: Evidence from porphyroblasts in the Betic Cordillera, Spain." Journal of Structural Geology 30, no. 10 (October 2008): 1272–87. http://dx.doi.org/10.1016/j.jsg.2008.06.009.

Full text

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!