scholarly journals Potential for Volcanogenic Massive Sulfide Mineralization at the A6 Anomaly, North-West British Columbia, Canada: Stratigraphy, Lithogeochemistry, and Alteration Mineralogy and Chemistry

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 867
Author(s):  
Stefanie M. Brueckner ◽  
Gregory Johnson ◽  
Stephanie Wafforn ◽  
Harold Gibson ◽  
Ross Sherlock ◽  
...  
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Isotope Composition ◽  
Massive Sulfide ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Volcanogenic Massive Sulfide ◽  
North West ◽  
Group A ◽  
Group B

The Middle Jurassic A6 Anomaly is located 30 km southeast of Eskay Creek, north-central British Columbia and consists of thick, altered felsic igneous rocks overlain by a mafic volcano-sedimentary package. Lithogeochemistry on igneous rocks, x-ray diffraction on altered felsic units, and electron probe microanalysis and secondary ion mass spectrometry on illite and quartz were applied to explore the volcanogenic massive sulfide (VMS) potential, characterize alteration, and determine fluid conditions at the A6 Anomaly. Lithogeochemistry revealed calc-alkaline rhyodacite to trachyte of predominantly FII type, tholeiitic basalts with Nb/Yb < 1.6 (i.e., Group A), and transitional to calc-alkaline basalts and andesites with Nb/Yb > 2.2 (i.e., Group B). The felsic units showed weakly to moderately phyllic alteration (quartz–illite with minor orthoclase and trace chlorite–pyrite–calcite–barite–rutile). Illite ranged in composition from illite/smectite (K = 0.5–0.69 apfu) to almost endmember illite (K = 0.69–0.8 apfu), and formed from feldspar destruction by mildly acidic, relatively low temperature, oxidized hydrothermal fluids. The average δ18O composition was 10.7 ± 3.0‰ and 13.4 ± 1.3‰ relative to Vienna Standard Mean Ocean Water for illite and quartz, respectively. Geothermometry involving illite composition and oxygen isotope composition on illite and quartz yielded average fluid temperatures of predominantly 200–250 °C. Lithogeochemical results showed that the A6 Anomaly occurred in a late-Early to Middle Jurassic evolving back-arc basin, further east then previously recognized and in which transitional to calc-alkaline units formed by crustal assimilation to enriched Mid-Ocean Ridge Basalt (EMORB) (i.e., felsic units, Group B), followed by thinning of the crust resulting in tholeiitic normalized MORB basalts (i.e., Group A) with a minor crustal component. The alteration assemblage is representative of distal footwall alteration, and metal transport in this zone was limited despite favorable temperature, pH, and redox state, indicating a metal depleted source (i.e., felsic units).

Spatial and temporal influence of Pacific subduction on South China: geochemical migration of Cretaceous mafic–intermediate rocks

2020 ◽  
Vol 177 (5) ◽  
pp. 1013-1024
Author(s):  
Chengshi Gan ◽  
Yuejun Wang ◽  
Tiffany L. Barry ◽  
Yuzhi Zhang ◽  
Xin Qian
Keyword(s):  
South China ◽  
Igneous Rocks ◽  
Geochemical Data ◽  
Content Type ◽  
The Pacific ◽  
Group A ◽  
Temporal Influence ◽  
Pacific Slab ◽  
Supplementary Material ◽  
Group B

The Cretaceous igneous rocks in the South China Block (SCB) were associated with the slab subduction and roll-back of the Pacific Plate. Thus, they provide excellent opportunities to examine the spatial–temporal geochemical migration of magmatism in the retreating subduction margins. The Cretaceous mafic–intermediate igneous rocks from the southeastern SCB were aged between 142 and 71 Ma, and can geochemically be subdivided into three groups: Group A (126–129 Ma and 83–93 Ma), Group B (126–142 Ma and 71–108 Ma) and Group C (116–142 Ma and 70–110 Ma). Group A and B were mainly distributed in the SCB interior and derived from asthenosphere and asthenosphere–lithosphere interaction sources, respectively. Group C occurred to the east of the Ganjiang Fault and originated from slab–lithosphere interaction. From the coastal provinces to the interior, these mafic–intermediate igneous rocks show increasing incompatible element ratios and Nd isotopic compositions, reflective of a westerly decreasing involvement of slab-derived components. They show two similar age-pulses at c. 125 Ma and c. 90 Ma as well as the Cretaceous A-type granites, indicating two episodes of subduction retreat of the Pacific slab during the Cretaceous. This spatial–temporal pattern of the Cretaceous mafic–intermediate igneous rocks suggests that the Cretaceous slab metasomatism of Pacific subduction retreat was limited to the east of the Ganjiang Fault.Supplementary material: Tables of geochemical data and additional figures are available at https://doi.org/10.6084/m9.figshare.c.4938576

Paleozoic volcanic assemblages and volcanogenic massive sulfide deposits near Tulsequah, British Columbia

1984 ◽  
Vol 21 (3) ◽  
pp. 379-381
Author(s):  
Joanne Nelson ◽  
John G. Payne
Keyword(s):  
British Columbia ◽  
Sedimentary Rocks ◽  
Massive Sulfide ◽  
Late Triassic ◽  
Late Paleozoic ◽  
Volcanogenic Massive Sulfide ◽  
Small Bodies ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits ◽  
Volcanogenic Massive Sulfide Deposits

New fossil, structural, and lithological evidence shows that the dominantly andesitic terrane near the junction of the Taku and Tulsequah rivers, northwestern British Columbia, is a proximal facies, roughly age equivalent to late Paleozoic tuffaceous and argillaceous sedimentary rocks exposed near Tatsamenie Lake, rather than of Late Triassic age as previously mapped. Fusulinids from the Tulsequah sequence are Middle Pennsylvanian, whereas the limestones at the top of the Paleozoic section near Tatsamenie Lake are of Permian age. The Tulsequah sequence hosts the Tulsequah Chief, Big Bull, and Ericksen – Ashby massive sulfide deposits, which arc associated with small bodies of rhyolite.

Lower to Middle Jurassic (Pliensbachian to Bajocian) stratigraphy of the northern Spatsizi area, north-central British Columbia

1986 ◽  
Vol 23 (12) ◽  
pp. 1963-1973 ◽  
Author(s):  
Robert C. Thomson ◽  
Paul L. Smith ◽  
Howard W. Tipper
Keyword(s):  
British Columbia ◽  
Grain Size ◽  
Middle Jurassic ◽  
Water Environment ◽  
Upper Jurassic ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
North Central ◽  
Area North ◽  
Southern Flank

The Lower to Middle Jurassic (Pliensbachian to lower Bajocian) Spatsizi Group in the northern Spatsizi area of north-central British Columbia is formally defined and subdivided into the Joan, Wolf Den, Melisson, Abou, and Quock formations. Each formation reflects deposition in a different, dominantly fine-clastic environment with a varying input of volcanic (epiclastic or pyroclastic) detritus. The Spatsizi Group represents the basinward sedimentary equivalent of the coeval Cold Fish Volcanics, a group of calc-alkaline flows and breccias that accumulated in a volcanic arc along the southern flank of the Stikine Arch. Arc-to basin-facies trends are best developed in the Joan and Wolf Den formations and are characterized by a decrease in the volcaniclastic component of the sediments, an overall reduction in grain size, and a progressively deeper water environment of deposition, as inferred from both sedimentological and faunal evidence.In the study area, the Spatsizi Group underlies with a slight angular discordance the Middle to Upper Jurassic Bowser Lake Group. Bowser lake sediments were deposited in the Bowser Basin, the largest Mesozoic successor basin in British Columbia. Based on evidence from the Spatsizi area and from other areas to the south at Diagonal Mountain and the Oweegee Mountains, the Spatsizi Group is interpreted as passing laterally into shales that underlie most of the Bowser Basin.

Beakers: Deconstruction and After

1993 ◽  
Vol 59 ◽  
pp. 241-268 ◽  
Author(s):  
Humphrey Case
Keyword(s):  
Western Europe ◽  
Late Neolithic ◽  
East Anglia ◽  
North West ◽  
The North ◽  
Group A ◽  
The North Sea ◽  
Bell Beaker ◽  
South East England ◽  
Group B

Taking grave and non-grave pottery together, five summary regional groups of beaker pottery are proposed for Britain and Ireland: Group A, Ireland; Group B, north Britain and eventually widespread; Group C, north and to some extent south Britain; Group D, south Britain; and Group E, East Anglia and south-east England. It is anticipated that further discoveries and research will enable these groups to be refined regionally.These groups are set in a quarter-millennium calendrical chronology, which suggests that they may all have appeared around or near the mid-3rd millennium BC, and that many of their aspects were long enduring, some surviving to the 2nd quarter of the 2nd millennium BC.Decorative features especially are related to bell-beaker pottery in western Europe, to Single Grave pottery across the North Sea, and to native Late Neolithic pottery. In presenting the chronology of these relationships, it is argued that a widely held view that bell-beaker pottery evolved in north-west Europe requires modification.

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