scholarly journals Zeolites filling cavities and amigdales of basic volcanic rocks in NW of Davazdah-Emam mountain, north Central Iran

2018 ◽  
Vol 26 (3) ◽  
pp. 597-610
Author(s):  
sahar Koohfar ◽  
Amirali Tabbakh Shabani ◽  
kamalodin Bazargani-Guilani ◽  
Morteza Delavari Kooshan ◽  
◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Central Iran ◽  
North Central ◽  
Basic Volcanic

Petrology, geochemistry and tectonics of the Sabzevar ophiolite, North Central Iran

2003 ◽  
Vol 21 (9) ◽  
pp. 1053-1067 ◽  
Author(s):  
B Shojaat ◽  
A.A Hassanipak ◽  
K Mobasher ◽  
A.M Ghazi
Keyword(s):  
Central Iran ◽  
North Central

scholarly journals Gold-hosting supracrustal rocks on Storø, southern West Greenland: lithologies and geological environment

2007 ◽  
Vol 13 ◽  
pp. 41-44 ◽  
Author(s):  
Christian Knudsen ◽  
Jeroen A.M. Van Gool ◽  
Claus Østergaard ◽  
Julie A. Hollis ◽  
Matilde Rink-Jørgensen ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
West Greenland ◽  
Metasedimentary Rocks ◽  
Quartz Veins ◽  
Rock Types ◽  
Minimum Age ◽  
Arc Setting ◽  
Basic Volcanic ◽  
Back Arc ◽  
Different Sources

A gold prospect on central Storø in the Nuuk region of southern West Greenland is hosted by a sequence of intensely deformed, amphibolite facies supracrustal rocks of late Mesoto Neoarchaean age. The prospect is at present being explored by the Greenlandic mining company NunaMinerals A/S. Amphibolites likely to be derived from basaltic volcanic rocks dominate, and ultrabasic to intermediate rocks are also interpreted to be derived from volcanic rocks. The sequence also contains metasedimentary rocks including quartzites and cordierite-, sillimanite-, garnet- and biotite-bearing aluminous gneisses. The metasediments contain detrital zircon from different sources indicating a maximum age of the mineralisation of c. 2.8 Ga. The original deposition of the various rock types is believed to have taken place in a back-arc setting. Gold is mainly hosted in garnet- and biotite-rich zones in amphibolites often associated with quartz veins. Gold has been found within garnets indicating that the mineralisation is pre-metamorphic, which points to a minimum age of the mineralisation of c. 2.6 Ga. The geochemistry of the goldbearing zones indicates that the initial gold mineralisation is tied to fluid-induced sericitisation of a basic volcanic protolith. The hosting rocks and the mineralisation are affected by several generations of folding.

Density determinations of basic volcanic rocks of the Yellowknife supergroup by gravity measurements in mine shafts—Yellowknife, Northwest Territories

Geophysics ◽  
1980 ◽  
Vol 45 (1) ◽  
pp. 18-31 ◽  
Author(s):  
R. A. Gibb ◽  
M. D. Thomas
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Mine Shaft ◽  
Average Interval ◽  
Basaltic Rocks ◽  
Surface Samples ◽  
Gravity Measurements ◽  
Vertical Density ◽  
Basic Volcanic

Gravity measurements were made in two gold mine shafts sunk in the Archean Yellowknife greenstone belt to determine the in‐situ densities of basic volcanic rocks of the Kam formation, Yellowknife supergroup. Thirteen stations were occupied between the surface and a depth of 608 m at an average interval of about 50 m in the C shaft of Giant Yellowknife Mines Limited, and 14 stations were occupied between the surface and a depth of 1598 m at an average interval of about 120 m in the Robertson shaft of Con mine, Cominco Limited. Densities were computed using the terminology of borehole gravimetry with appropriate corrections for surface terrain and underground voids such as shafts, drifts, and stopes. Weighted mean in‐situ densities of [Formula: see text] (36 to 608 m depth) and [Formula: see text] (surface to 1598 m depth) were obtained from the gravity measurements for the Giant and Robertson sections, respectively; these values compare with mean densities of 2.82 and [Formula: see text] obtained from rock samples collected at the underground gravity stations. Sheared specimens and massive specimens collected at both underground and surface gravity stations have mean densities of 2.80 and [Formula: see text], respectively. Unaltered surface samples collected at stratigraphic intervals of about 150 m throughout the entire volcanic sequence have a mean density of [Formula: see text]. Core samples obtained from holes drilled from the bottom of C shaft extend the vertical density profile for the Giant section from a depth of 608 to 1416 m; the mean density of these samples is [Formula: see text]. The lower bulk densities obtained from the mine shaft experiments reflect in part the high proportion of sheared rocks and in part the presence of lower‐density members of the Kam formation (andesite, dacite, tuff, breccia, and agglomerate) in the vicinity of the shafts, as opposed to purely massive basaltic rocks. A density of [Formula: see text] based on the proportion of low‐ and high‐density rocks in the volcanic belt is considered to be more representative of the Kam formation as a whole.

Mapping Quaternary faults in the west of Kavir Plain, north-central Iran, from satellite imageries

2010 ◽  
Vol 31 (19) ◽  
pp. 5111-5125 ◽  
Author(s):  
A. Babaahmadi ◽  
A. Yassaghi ◽  
A. Naeimi ◽  
GH. R. Dini ◽  
S. Taghipour
Keyword(s):  
Central Iran ◽  
The West ◽  
North Central

Nina Creek Group and Lay Range Assemblage, north-central British Columbia: remnants of late Paleozoic oceanic and arc terranes

1997 ◽  
Vol 34 (6) ◽  
pp. 854-874 ◽  
Author(s):  
Filippo Ferri
Keyword(s):  
British Columbia ◽  
North America ◽  
Volcanic Rocks ◽  
Tholeiitic Basalt ◽  
Ocean Floor ◽  
North Central ◽  
Marginal Basin ◽  
The North ◽  
Lower Division ◽  
Ocean Ridge

In north-central British Columbia, a belt of upper Paleozoic volcanic and sedimentary rocks lies between Mesozoic arc rocks of Quesnellia and Ancestral North America. These rocks belong to two distinct terranes: the Nina Creek Group of the Slide Mountain terrane and the Lay Range Assemblage of the Quesnel terrane. The Nina Creek Group is composed of Mississippian to Late Permian argillite, chert, and mid-ocean-ridge tholeiitic basalt, formed in an ocean-floor setting. The sedimentary and volcanic rocks, the Mount Howell and Pillow Ridge successions, respectively, form discrete, generally coeval sequences interpreted as facies equivalents that have been interleaved by thrusting. The entire assemblage has been faulted against the Cassiar terrane of the North American miogeocline. West of the Nina Creek Group is the Lay Range Assemblage, correlated with the Harper Ranch subterrane of Quesnellia. It includes a lower division of Mississippian to Early Pennsylvanian sedimentary and volcanic rocks, some with continental affinity, and an upper division of Permian island-arc, basaltic tuffs and lavas containing detrital quartz and zircons of Proterozoic age. Tuffaceous horizons in the Nina Creek Group imply stratigraphic links to a volcanic-arc terrane, which is inferred to be the Lay Range Assemblage. Similarly, gritty horizons in the lower part of the Nina Creek Group suggest links to the paleocontinental margin to the east. It is assumed that the Lay Range Assemblage accumulated on a piece of continental crust that rifted away from ancestral North America in the Late Devonian to Early Mississippian by the westward migration of a west-facing arc. The back-arc extension produced the Slide Mountain marginal basin in which the Nina Creek Group was deposited. Arc volcanism in the Lay Range Assemblage and other members of the Harper Ranch subterrane was episodic rather than continuous, as was ocean-floor volcanism in the marginal basin. The basin probably grew to a width of hundreds rather than thousands of kilometres.

Thermodynamic regime of greenstone metamorphism of basic volcanic rocks after experimental data

1981 ◽  
Vol 18 (8) ◽  
pp. 1303-1309 ◽  
Author(s):  
L. P. Pluysnina ◽  
I. P. Ivanov
Keyword(s):  
Stability Boundary ◽  
Salt Content ◽  
Volcanic Rocks ◽  
Fe Content ◽  
Low Salt ◽  
Thermodynamic Regime ◽  
Lower Temperature ◽  
The Stability ◽  
Basic Volcanic ◽  
Facies Transition

The stability fields of laumontite, prehnite, pumpellyite, zoisite, and tremolite-bearing assemblages were experimentally examined in the CaO–MgO–Al2O3–SiO2–H2O–CO2 system. The influence of the Fe content on the shift of the upper stability boundary towards both lower temperature and [Formula: see text] equilibrium values is shown for pumpellyite. The runs for some dehydration–carbonatization reactions in the complex H2O–CO2–NaCl fluid have revealed a decrease in the [Formula: see text] equilibrium values for even low salt content. The zeolite, prehnite–pumpellyite, and greenschist facies limits are plotted in the schematic [Formula: see text] diagram, and their possible Pfl limits are discussed. For examined P–T conditions of greenschist to amphibolite facies transition the absence of the compositional gap between tremolite and Ca-hornblende is found.

Detrital modes of the Riding Island Graywacke, north-central Newfoundland: evidence for deposition in a collisional successor basin in the Dunnage Zone

1994 ◽  
Vol 31 (1) ◽  
pp. 176-181 ◽  
Author(s):  
Gary G. Lash
Keyword(s):  
Volcanic Rocks ◽  
Island Arc ◽  
North Central ◽  
Arc Volcanism ◽  
Tectonic Environment ◽  
Complex Source ◽  
Island Arc Volcanism ◽  
Sandstone Provenance ◽  
Silicic Volcanic ◽  
Terrane Accretion

The Riding Island Graywacke (late Caradoc – Ashgill) crops out in Notre Dame Bay, north-central Newfoundland. Previous tectonic interpretations suggest that this succession of turbidites and hemipelagic mudstone accumulated in a basin adjacent to an active volcanic arc. The varied framework mineralogy of 29 Riding Island samples studied, however, records derivation from a complex source terrane composed of mafic and silicic volcanic rocks, sedimentary and metamorphic successions, and plutonic rocks. Assessment of the tectonic environment of deposition of the Riding Island Graywacke by use of popular sandstone provenance ternary diagrams yields ambiguous results. The mineralogy of the Riding Island samples reveals a change in tectonic scenario from one dominated by island-arc volcanism in pre-Caradoc time to a setting marked by tectonic shortening, transcurrent faulting, and terrane accretion near the end of the Ordovician. The complex composition of these sandstones and the fact that they accumulated after island-arc volcanism had ended argue for deposition in a collisional successor basin that formed during the early stages of mountain building along the proto-North American continental margin. This inferred Late Ordovician collisional successor basin may have also been the locus of deposition for other minera-logically complex late Caradoc – Ashgill units exposed in Notre Dame Bay, such as the Sansom Formation.

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