Experimental studies of pegmatite genesis; l, A model for the derivation and crystallization of granitic pegmatites

Jahns, Richard H.; Burnham, Charles W.

doi:10.2113/gsecongeo.64.8.843

Cited by 504 publications

(182 citation statements)

References 0 publications

Supporting

Mentioning

159

Contrasting

Unclassified

Order By: Relevance

“…As the alteration halos developed adjacent to the pegmatitic or aplitic veins, crystallising volatile-rich melts are the likely source of the infiltrating fluids, in accordance with the large grain-size of the pegmatitic veins indicating a volatile-rich melt (e.g. Jahns and Burnham, 1969). The solubility of H 2 O in a melt of granitic composition at nearsolidus temperatures is about 6 wt.% at 2 kbar and 10 wt.% at 4 kbar (Burnham, 1979).…”

Section: Fluid Infiltration Causing Alterationmentioning

confidence: 84%

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Engvik

Bertram

Kalthoff

et al. 2005

Journal of Structural Geology

View full text Add to dashboard Cite

Excellent outcrops in Dronning Maud Land, Antarctica, provide unique insight into the mode and extent of fluid infiltration into metamorphic and plutonic rocks in the middle crust. The fluids are liberated from pegmatitic veins and give rise to alteration halos. In the alteration halos, the conspicuous change in colour is correlated with (1) hydration mineral reactions, and (2) high density of microcracks in quartz and feldspar exceeding that observed in the unaltered host rock by an order of magnitude. The field relations indicate that the veins originated as melt-driven hydraulic fractures, sealed by pegmatite and aplite crystallising from volatile-rich melts, with the alteration halo being the wake of the process zone formed at the tip of the propagating fractures. It is proposed that (1) the size of the alteration zone and the width of the vein are correlated, resulting in higher values of both these quantities for cracks propagating at higher velocities and consequently higher crack propagation toughnesses; (2) the damage zone is characterised by a transient state of high permeability which was short-lived due to rapid healing and sealing of microcracks; (3) the infiltration and retrogression of the high-grade rocks can be considered as a quasi-instantaneous process on geologic time scales with a duration of hours to weeks. q

show abstract

Section: Fluid Infiltration Causing Alterationmentioning

confidence: 84%

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Engvik

Bertram

Kalthoff

et al. 2005

Journal of Structural Geology

View full text Add to dashboard Cite

show abstract

“…Secondly, the very much lower viscosity of pegmatitic fluids (10-3-10-4 poise, cf. 106-107 poise for hydrous granite magmas; Jahns and Burnham, 1969) will lead to very much greater crystal growth rates and diffusion rates than obtained for a hydrous granite magma. Consequently, in coexisting aplite magma and pegmatitic fluids at chemical equilibrium, and at the same temperature and pressure, the degree of supersaturation with respect to a given mineral species may be the same for both the silicate and hydrous phase, but differences in crystal morphology will arise as a consequence of the different physical properties of each phase.…”

Section: Field Relations Of the Samples Used In This Studymentioning

confidence: 93%

Chemical and morphological variation in tourmalines from the Hub Kapong batholith of peninsular Thailand

Manning

1982

Mineral. mag.

View full text Add to dashboard Cite

Electron probe microanalysis of tourmaline from late-stage aplites and mineralized (Sn-W) pegmatites from the Hub Kapong batholith of peninsular Thailand has revealed considerable chemical variation, and has shown that skeletal tourmaline crystals predominate within the pegmatites. The tourmalines show substitution towards the schorl end-member of the schorl-dravite series, as well as substitution towards alkali-free or proton deficient tourmaline. The extent of both substitutions increases (a) from aplites to pegmatites and (b) from core to rim within a single grain and so is believed to become greater with increasing degrees of differentiation of the aplite-pegmatite system. The development of skeletal crystals within the pegmatites and non-skeletal crystals within the aplites is believed to be due to the different kinetics of crystal growth obtaining within a hydrous, pegmatitic, fluid (viz. heterogeneous nucleation and comparatively rapid crystal growth rates) which in turn arise from differences in the structure of the aplitic magma and pegmatitic fluid. The observed chemical and morphological variation shown by the tourmalines is used to discuss the petrogenesis of the aplites and pegmatites, and associated ore deposits. During differentiation, the volatile content of the aplite magmas increased, leading to water saturation and the separation of a hydrous pegmatitic fluid. After a period of coexistence, possibly in chemical equilibrium, the crystallization of the pegmatites continued once the aplite magma had completely consolidated.

show abstract

“…The sample was crushed and sub-sampled. A number of experimental studies utilized this Spruce Pine sample (Jahns and Burnham 1957, 1969Burnham andJahns 1958, 1962;Burnham 1967;Vaughan 1963;Fenn 1986;Swanson and Fenn 1986).…”

Section: Introductionmentioning

confidence: 99%

Mineralogy and petrogenesis of pegmatites in the Spruce Pine District, North Carolina, USA

Swanson¹,

Veal²

2012

J. Geosci.

View full text Add to dashboard Cite

Granitic rocks (mainly granodiorites) of the Spruce Pine Plutonic Suite occur as small plutons and numerous pegmatite bodies intruded into amphibolite-grade schists and gneisses of the Ashe Formation. Intrusion ages range from 377 to 404 Ma and are near the peak of amphibolite-facies metamorphism in the country rocks. The granodiorites have a mortar texture with coarse (~ 1 cm) grains of feldspar, quartz and muscovite enclosed in a finer grained matrix of the same phases. Large (10-30 cm) crystals of perthitic K-feldspar and plagioclase occur in the granodiorite. Pegmatites occur within the granodiorite and as isolated intrusions within the country rocks. Contacts between pegmatites and host granodiorites range from sharp, cross-cutting to completely gradational. Some of the plutons contain up to 50 % pegmatite. Pegmatite mineralogy is similar to the granodiorites; major amounts of feldspars and quartz, accessory amounts of muscovite, garnet, and epidote. Secondary minerals, formed by subsolidus recrystallization, include epidote, muscovite, quartz, and grossular garnet. A few of the pegmatites are more fractionated and contain tourmaline and beryl. Compositions of feldspars, muscovite, and garnet show some regional variation, but are generally similar for pegmatites and associated granodiorite. About half of the pegmatites are unzoned. Zoning in the pegmatites is simple with a quartz core, an intermediate zone of graphic granite, plagioclase and muscovite and an outer finer grained zone that locally shows mineral layering parallel to the contact. The abundance of pegmatitic textures relative to granitoid textures in the Spruce Pine Plutonic Suite is related to the depth of crystallization. Spruce Pine granitoids crystallized at depths of 20-30 km (0.7 to 1.1 GPa ) based on feldspar thermobarometry and experimentally determined melting relations. Skeletal crystals of quartz and feldspar along with plumose muscovite clusters are common in the Spruce Pine pegmatites. Water content of magmas at such high pressures can be high. The subtle transition from granitic to pegmatitic texture so common at Spruce Pine (and in other deep-seated systems) was probably related to the development of zones of water-enriched magma and delayed nucleation in the hydrous melts. Deformation (evidenced by mortar texture) of the Spruce Pine Plutonic Suite was related to later regional deformation.

show abstract

Experimental studies of pegmatite genesis; l, A model for the derivation and crystallization of granitic pegmatites

Cited by 504 publications

References 0 publications

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica

Chemical and morphological variation in tourmalines from the Hub Kapong batholith of peninsular Thailand

Mineralogy and petrogenesis of pegmatites in the Spruce Pine District, North Carolina, USA

Contact Info

Product

Resources

About