Contact Metamorphism in Relation to Manner of Emplacement of the Granites of Donegal, Ireland: A Discussion

1964 ◽  
Vol 72 (5) ◽  
pp. 682-684
Author(s):  
M. J. Rickard
Keyword(s):  
Contact Metamorphism

Antigorite-ophicarbonates: Contact metamorphism in Valmalenco, Italy

1977 ◽  
Vol 62 (3) ◽  
pp. 301-312 ◽  
Author(s):  
Volkmar Trommsdorff ◽  
Bernard W. Evans
Keyword(s):  
Contact Metamorphism

Contact metamorphism around the Stawell granite, Victoria, Australia

1994 ◽  
Vol 12 (5) ◽  
pp. 609-624 ◽  
Author(s):  
G. XU ◽  
R. POWELL ◽  
C. J. L. WILSON ◽  
T. M. WILL
Keyword(s):  
Contact Metamorphism

Shale gas leakage in lower Ecca shales during contact metamorphism by dolerite sill intrusions in the Karoo Basin, South Africa

2021 ◽  
Author(s):  
V. Nengovhela ◽  
B. Linol ◽  
L. Bezuidenhout ◽  
T. Dhansay ◽  
T Muedi ◽  
...  
Keyword(s):  
South Africa ◽  
Grain Boundaries ◽  
Shale Gas ◽  
Elevated Temperatures ◽  
Contact Metamorphism ◽  
Microscopy Imaging ◽  
Gas Leakage ◽  
Karoo Basin ◽  
Maximum Temperatures ◽  
Host Rocks

Abstract Contact metamorphism along widespread dolerite sills and dykes, emplaced at 182 to 183 Ma through the sedimentary host rocks of the Karoo Basin, triggered devolatilization of carbon-rich shales of the Lower Ecca Group. Hornfel samples collected from drill cores that intersect dolerite sills were analyzed for mineral phase equilibria, chemistry and porosity to characterize thermal aureoles at various distances from sill intrusions. Andalusite-chiastolite and cordierite porphyroblasts with biotite and muscovite occur within 10 to 20 m of many intrusive contacts. These metamorphic minerals crystallized when host shales attained maximum temperatures ranging between 450 and 600°C. Scanning electron microscopy imaging confirms that the hornfels are compact and that their metamorphic minerals limit porosity along grain boundaries. In few cases intra-mineral porosity occurs within individual crystals such as calcite, andalusite and cordierite. Disequilibrium metamorphic textures such as irregular grain boundaries, and inclusions in andalusite and cordierite reveal that the elevated temperatures were too short-lived to accomplish complete (re)crystallization. Thermal modeling results are consistent with the observed metamorphic mineral assemblages. Gas leakage calculations along a 7 m and a 47 m thick dolerite sill that intrude toward the top of the Whitehill Formation suggest that methane volumes ranging between 8 to 15 Tcf were generated during the sill emplacement. Methane was likely released into the atmosphere through hydrothermal vent complexes that are well preserved in the western Karoo Basin. If such loss was widespread across the entire basin, the implications for paleo-climate change and preserved shale gas reserves in the Karoo Basin of South Africa would be significant.

scholarly journals VI.—On the occurrence of Corundum produced by Contact-metamorphism on Dartmoor

1896 ◽  
Vol 3 (11) ◽  
pp. 492-494 ◽  
Author(s):  
K. Busz
Keyword(s):  
Contact Metamorphism ◽  
General Interest

Some three years ago, when travelling in Devonshire, I had the opportunity of visiting some places on Dartmoor, and of collecting on the border of the Dartmoor Granite some specimens of rocks, which on closer examination seemed to be of general interest. Although I have not finished the examination of these, yet I have made some remarkable observations, which I should like to describe to the readers of this Magazine.

scholarly journals Widespread hydrothermal vents and associated volcanism record prolonged Cenozoic magmatism in the South China Sea

2021 ◽  
Author(s):  
Fang Zhao ◽  
Christian Berndt ◽  
Tiago M. Alves ◽  
Shaohong Xia ◽  
Lin Li ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Margin ◽  
South China ◽  
Hydrothermal Vents ◽  
Northern South China Sea ◽  
Contact Metamorphism ◽  
Magnetic Data ◽  
Geochemical Data ◽  
Time Interval ◽  
China Sea

The continental margin of the northern South China Sea is considered to be a magma-poor rifted margin. This work uses new seismic, bathymetric, gravity, and magnetic data to reveal how extensively magmatic processes have reshaped the latter continental margin. Widespread hydrothermal vent complexes and magmatic edifices such as volcanoes, igneous sills, lava flows, and associated domes are confirmed in the broader area of the northern South China Sea. Newly identified hydrothermal vents have crater- and mound-shaped surface expressions, and occur chiefly above igneous sills and volcanic edifices. Detailed stratigraphic analyses of volcanoes and hydrothermal vents suggest that magmatic activity took place in discrete phases between the early Miocene and the Quaternary. Importantly, the occurrence of hydrothermal vents close to the present seafloor, when accompanied by shallow igneous sills, suggest that fluid seepage is still active, well after main phases of volcanism previously documented in the literature. After combining geophysical and geochemical data, this study postulates that the extensive post-rift magmatism in the northern South China Sea is linked to the effect of a mantle plume over a long time interval. We propose that prolonged magmatism resulted in contact metamorphism in carbon-rich sediments, producing large amounts of hydrothermal fluid along the northern South China Sea. Similar processes are expected in parts of magma-poor margins in association with CO2/CH4 and heat flow release into sea water and underlying strata.

Contact metamorphism of the Ellsworth schist near Blue Hill, Maine

1929 ◽  
Vol 24 (2) ◽  
pp. 182-194
Author(s):  
Joseph Lincoln Gillson ◽  
R. M. Williams
Keyword(s):  
Contact Metamorphism

scholarly journals IV.—An Interesting Contact-Rock, with Notes on Contact-Metamorphism

1895 ◽  
Vol 2 (3) ◽  
pp. 122-131 ◽  
Author(s):  
W. Maynard Hutchings
Keyword(s):  
Contact Metamorphism ◽  
Considerable Time ◽  
Joint Work

For a considerable time past I have been engaged, in collaboration with Mr. E. J. Garwood, in an investigation of the rocks in contact with the Whin Sill. The results of our joint work, geological, petrographical, and chemical, will be published in detail in due course. In the meantime there are some special observations, made on some of the rocks in question, which have more or less bearing on some of the points dealt with in a paper I contributed to the Geological Magazine last year (Geol. Mag. 1894, pp. 36 and 64).

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