scholarly journals Petrographic features of Siluro-Devonian feisic volcanic rocks in the Riley Brook area, Tobique Zone, New Brunswick: implications for base metal mineralization at Sewell Brook

10.4138/1854 ◽  
1992 ◽  
Vol 28 (1) ◽  
Author(s):  
R. A. Wilson
Keyword(s):  
New Brunswick ◽  
Base Metal ◽  
Volcanic Rocks ◽  
Base Metal Mineralization

Geology of the Caribou Deposit, Bathurst, New Brunswick

1971 ◽  
Vol 8 (9) ◽  
pp. 1125-1136 ◽  
Author(s):  
W. E. Roscoe
Keyword(s):  
New Brunswick ◽  
Transition Zone ◽  
Base Metal ◽  
Volcanic Rocks ◽  
Greenschist Facies ◽  
Structural Deformation ◽  
Hydrothermal Solutions ◽  
Limited Extent ◽  
The Core ◽  
Silicic Volcanic

The Caribou deposit occurs in a mixed volcanic–sedimentary zone which is transitional between graphitic argillite and silicic tuffaceous rocks. The silicic tuffaceous rocks form the core, and the graphitic argillite the outside, of the steeply plunging Caribou synform.The Ore Zone Unit consists of the volcanic–sedimentary transition zone and the sulfides. The Caribou deposit consists of three or more en echelon lenses of pyrite – sphalerite – galena – chalcopyrite and footwall disseminated sulfides. Sulfide zoning in the deposit indicates that the stratigraphic top is towards the silicic volcanic rocks. The deposit has a galena–sphalerite zone on the silicic volcanic side and the hangingwall contact is sharp. There is a chalcopyrite-rich zone on the sedimentary side and the contact is indistinct. Very fine spheres, cubes, and framboids of pyrite in both the deposit and the sedimentary wallrocks, as well as pyrite colloform structures in the deposit, appear to be relict primary or diagenetic structures.All the rocks, including the sulfides, have been regionally metamorphosed to lower greenschist facies and contain a pervasive slaty cleavage or schistosity, which is the earliest imprint of structural deformation. Pyrite, sphalerite, galena, chalcopyrite, arsenopyrite, quartz, stilpnomelane, and sericite are in a granoblastic intergrowth typical of metamorphosed sulfides. This early structural deformation has fractured and granulated pyrite and, to a limited extent, sphalerite; and chalcopyrite, galena, and sphalerite flowed plastically. The early slaty cleavage or schistosity has been deformed by minor structures and folded into the Caribou synform.Many features of the Caribou deposit and similarities to other volcanic-associated stratiform base metal deposits indicate a syngenetic origin involving submarine deposition of sulfides derived from volcanic, exhalative, hydrothermal solutions and possibly as pyroclastic debris.

Petrology and geochemistry of Cambrian volcanic rocks from the Avalon Zone in New Brunswick

1985 ◽  
Vol 22 (6) ◽  
pp. 881-892 ◽  
Author(s):  
John D. Greenough ◽  
S. R. McCutcheon ◽  
V. S. Papezik
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Middle Cambrian ◽  
Mafic Rocks ◽  
Rock Types ◽  
Petrology And Geochemistry ◽  
Eastern Seaboard ◽  
Highly Evolved

Lower to Middle Cambrian volcanic rocks occur within the Avalon Zone of southern New Brunswick at Beaver Harbour and in the Long Reach area. The Beaver Harbour rocks are intensely altered, but the major- and trace-element geochemistry indicates that they could be highly evolved (basaltic andesites) within-plate basalts. The mafic flows from the Long Reach area form two chemically and petrologically distinct groups: (1) basalts with feldspar phenocrysts that represent evolved continental tholeiites with some oceanic characteristics; and (2) a group of aphyric basalts showing extremely primitive continental tholeiite compositions, also with oceanic affinities and resembling some rift-related Jurassic basalts on the eastern seaboard. Felsic pyroclastic rocks in the Long Reach area make the suite bimodal. This distribution of rock types supports conclusions from the mafic rocks that the area experienced tension throughout the Early to Middle Cambrian.

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

2021 ◽  
Vol 57 ◽  
pp. 239-273
Author(s):  
Allan Ludman ◽  
Christopher McFarlane ◽  
Amber T.H. Whittaker
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
East Central ◽  
Arc Volcanism ◽  
Middle Ordovician ◽  
Volcanic Suite ◽  
Back Arc

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This >150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

Chapter 21: Geology of the Fruta del Norte Epithermal Gold-Silver Deposit, Ecuador

2020 ◽  
pp. 431-450
Author(s):  
Stephen Leary ◽  
Richard H. Sillitoe ◽  
Jorge Lema ◽  
Fernando Téliz ◽  
Diego Mena
Keyword(s):  
Base Metal ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Silver Deposit ◽  
Epithermal Gold ◽  
Mountain Ranges ◽  
The North ◽  
Pull Apart Basin ◽  
Gold Silver ◽  
A Minor

Abstract Fruta del Norte is a completely concealed and extremely well-preserved, Late Jurassic epithermal gold-silver deposit of both low- and intermediate-sulfidation type, which is located in the remote Subandean mountain ranges of southeastern Ecuador. Currently defined indicated resources are 23.8 million metric tons (Mt) averaging 9.61 g/t Au and the total endowment is 9.48 Moz Au. The deposit, notable for the widespread occurrence of visible gold and bonanza grades, will be bulk mined underground. Fruta del Norte was discovered in 2006 during greenfield exploration and systematic drill testing of a conceptual geologic model, which predicted that auriferous veins would occur in andesitic volcanic rocks inferred to underlie a zone of arsenic- and antimony-anomalous silicification in fluvial conglomerate. The host andesitic volcanic rocks, crosscutting feldspar porphyry, and associated phreatic breccia are part of a roof pendant in the Zamora batholith. Together, they are products of a continental-margin volcanoplutonic arc of Middle to Late Jurassic age. The deposit lies beneath the northern extremity of the ~16-km-long, Suárez pull-apart basin where it is localized by steep, second-order faults within the regionally extensive Las Peñas strike-slip fault zone. The pull-apart basin was progressively filled by fluvial conglomerate, dacitic ignimbrite, finer grained siliciclastic sedimentary rocks, and, finally, andesite flows. The Fruta del Norte deposit comprises a 1.3-km-long and up to >300-m-wide vein stockwork associated with quartz-illite-pyrite alteration. The deposit comprises two principal vein types, one in the south dominated by quartz, manganoan carbonates, and abundant base metal sulfides and the other in the north dominated by manganese- and base metal-poor quartz, chalcedony, and calcite. Adularia is a minor gangue mineral in both. Both vein types are abruptly transitional upward and westward to a third important ore type characterized by intense silicification and chalcedony veining, with disseminated and veinlet marcasite (± pyrite). An extensive silica sinter horizon directly overlies the andesitic rocks and/or occurs as interbeds in the lowermost 20 m of the conglomerate and, consequently, is in unusual proximity to the underlying gold-silver orebody. Much of the conglomerate lacks silicification except for a narrow, steeply inclined zone exposed above the deposit, which led to its discovery.

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