Successive zoning of Al and H in hydrothermal vein quartz

2005 ◽  
Vol 90 (2-3) ◽  
pp. 310-315 ◽  
Author(s):  
N. Miyoshi
2017 ◽  
Vol 43 (5) ◽  
pp. 2588
Author(s):  
S. Fadda ◽  
M. Fiori ◽  
S. Pretti ◽  
P. Valera

During the eastward drift of the Palaeozoic-Mesozoic block formed by Sardinia and Corsica in the Oligocene-Miocene, calc-alkaline volcanism developed mostly in the western part of the island. Most Tertiary metallogenic phoenomena are related to hydrothermal activity associated with this volcanism. Following volcanic and related hydrothermal activity, sediments were deposited during the Oligocene-Miocene as a consequence of a marine transgression. The basal part of this series is clastic and includes elements derived from erosion of unaltered volcanics as well as hydrothermally altered rocks and hydrothermal vein quartz. Inside the Tertiary volcanics manganese ore-minerals occur as nodules, veinlets, and stockworks and mainly include Mn and Fe oxides; quartz in different forms is the most common gangue mineral. The mineralisations at the contact between volcanics and Miocene sediments are the most homogeneous, the ore-minerals occur in the cement, but also as fairly continuous thin beds, nodules and veinlets containing pyrolusite, frequent ramsdellite, less frequent manganite, psilomelane, cryptomelane-manjiroite, rare ranciéite, and todorokite. The nature of the ore-bearing beds indicate a near-shore clastic environment along the ancient coastal lines of the Miocene sea. Genetic considerations point to a supergenic transport and redeposition after erosion of primary dispersion and residual concentrations of Mn in the volcanics.


2016 ◽  
Vol 37 ◽  
pp. 59-64
Author(s):  
V.M. Zagnitko ◽  
◽  
V.V. Shunko ◽  
I.V. Kvasnytsia ◽  
V.S. Sydorchuk ◽  
...  

1993 ◽  
Vol 20 (5) ◽  
Author(s):  
W.J. Rink ◽  
H. Rendell ◽  
E.A. Marseglia ◽  
B.J. Luff ◽  
P.D. Townsend

2021 ◽  
Vol 575 ◽  
pp. 120260
Author(s):  
Manuel Scharrer ◽  
Rebekka Reich ◽  
Tobias Fusswinkel ◽  
Benjamin F. Walter ◽  
Gregor Markl

1889 ◽  
Vol 6 (7) ◽  
pp. 315-318 ◽  
Author(s):  
T. G. Bonney

More than one kind of rock, as we learn from Dr. H. Hicks and other writers, occurs in the conglomerate which forms a well-marked base to the Cambrian system at St. Davids. Sometimes the pebbles are mainly vein quartz, sometimes felstone predominates, but occasionally, as in the neighbourhood of Nun's Chapel Bay, quartzites (using the term rather generally) are not uncommon. At one place, not far from a quartz-felsite dyke, these are rather large, occasionally about a foot in diameter. From this locality, while spending a few days at St. Davids in 1882, I brought away specimens of three of the most marked varieties of quartzite, of which I had slices prepared, thinking that as examples of rocks which were probably far from modern at the beginning of the Cambrian age, their structures might be instructive.


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