Mineralogy, bulk and rare earth element geochemistry of massive sulphide-associated hydrothermal sediments of the Brunswick Horizon, Bathurst Mining Camp, New Brunswick

1996 ◽  
Vol 33 (2) ◽  
pp. 252-283 ◽  
Author(s):  
Jan M. Peter ◽  
Wayne D. Goodfellow
Keyword(s):  
Rare Earth ◽  
Sea Water ◽  
Sedimentary Rocks ◽  
Massive Sulphide ◽  
Hydrothermal Fluids ◽  
Iron Formation ◽  
Element Geochemistry ◽  
Bathurst Mining Camp ◽  
Felsic Volcanic ◽  
Ree Patterns

Massive sulphides are spatially and temporally associated with iron formation (IF) and other hydrothermal sedimentary rocks in the vicinity of the Brunswick No. 12, Brunswick No. 6, and Austin Brook deposits, Bathurst Mining Camp. Sulphide-, carbonate-, oxide-, and silicate-predominant IF is present. Carbonate-predominant IF is best developed in and around the Brunswick No. 12 deposit, whereas hematite-bearing IF is absent here but prominent in the Austin Brook–Brunswick No. 6 area. The IF is composed dominantly of Si, CO2, Fe, Mn, and Ca. Minor constituents include Mg, P, Ti, Al, and S. Statistically significant interelement correlations between Eu, Fe, Mn, Pb, Zn, Cd, Au, Ca, Sr, Ba, P, CO2, and S indicate that these elements were precipitated from hydrothermal fluids vented onto the seafloor. Positive interelement correlations between Si, Ti, Al, Mg, K, Zr, rare earth elements (REE's) except Eu, Se, V, Y, Yb, Co, Ni, and Cr reflect the presence of detrital clastic mafic and aluminosilicate minerals and hydrogenous sedimentary components. Felsic volcanic and pyroclastic rocks are considered to be the source for the detritus. REE patterns of IF at Brunswick No. 12 display similarities with those of modern high-temperature hydrothermal vent solutions, sea water, and host rhyolitic tuff and sedimentary rocks. These patterns are largely controlled by the relative proportions of hydrothermal and detrital components. The IF formed from reduced hydrothermal fluids vented into a stratified marine basin. The mineral precipitates were widely dispersed from the sites of venting and massive sulphide accumulation.

Intense silicification of footwall sedimentary rocks in the stockwork alteration zone beneath the Brunswick No. 12 massive sulphide deposit, Bathurst, New Brunswick

1996 ◽  
Vol 33 (2) ◽  
pp. 284-302 ◽  
Author(s):  
David R. Lentz ◽  
Wayne D. Goodfellow
Keyword(s):  
New Brunswick ◽  
Sea Water ◽  
Sedimentary Rocks ◽  
Massive Sulphide ◽  
Iron Formation ◽  
Alteration Zone ◽  
Massive Sulphide Deposit ◽  
Sulphide Deposit ◽  
Fine Grained ◽  
Balance Analysis

Intensely silicified volcaniclastic mudstones that underlie the Brunswick No. 12 massive sulphide deposit in northern New Brunswick resemble silicified rocks described in the immediate footwall of many ancient and modern massive sulphide deposits. The white to grey, cryptocrystalline silica in the silicified rocks becomes more common with proximity to the vent, and is most abundant immediately below the massive sulphide zone. Mass-balance analysis of altered footwall sedimentary rocks on the 850 m level of the mine shows that SiO2 increases up to 300%. The high silica enrichment in the feeder zone is consistent with the presence of cherty silica in the massive sulphides and in associated exhalative iron formation. Coincident with silicification are enrichments in S, FeOt, MgO, MnO, CaO, P2O5, F, Cl, Y, Cu, Co, Cr, and Ni, as well as light rare earth elements and Eu. Oxygen isotope analyses of chloritized and silicified footwall sedimentary rocks suggest that the hydrothermal fluid had a δ18O composition of approximately 4[Formula: see text] and probably was dominated by chemically modified sea water. Rapid oversaturation of the silica-bearing fluid likely explains the intensity and fine-grained nature of this silicification, although the actual mechanism for this oversaturation is uncertain.

Rare-earth-element geochemistry of some Archean iron formations north of Lake Superior, Ontario

1988 ◽  
Vol 25 (4) ◽  
pp. 570-580 ◽  
Author(s):  
T. J. Barrett ◽  
P. W. Fralick ◽  
I. Jarvis
Keyword(s):  
Rare Earth ◽  
Red Sea ◽  
Rare Earth Element ◽  
Earth Element ◽  
Sea Water ◽  
Iron Formation ◽  
Submarine Fan ◽  
Eu Anomaly ◽  
Ree Patterns ◽  
Iron Formations

Rare-earth-element (REE) compositions of iron formation from two Archean terrains in western Ontario have been determined in order to assess the possible influence of hydrothermal activity on the REE patterns of chemical sediments. One terrain is characterized by sulfide-facies iron formation in association with volcanic flows and volcaniclastic sediments, whereas the other is dominated by oxide-facies iron formation intercalated within submarine-fan clastic sediments. Mineral separates of chert, magnetite, and pyrite from the iron formations have low ΣREE concentrations (< 20–30 ppm) and display moderate to strong positive Eu anomalies (relative to Archean shale). The positive anomalies (and lack of negative Ce anomalies) indicate that Archean sea water from which iron formation locally precipitated was reduced, although to varying degrees.The REE patterns of mineral separates from a given locality are almost identical, but the patterns for various localities differ in detail. A number of iron-formation samples interbedded within volcanics and at the volcanic–sediment interface show a distinct positive La anomaly and near-flat to slightly heavy-REE (HREE)-enriched patterns. The only modern environment where metalliferous sediments are accumulating with these combined characteristics is the Red Sea brine deeps. By contrast, limited data from iron formation interbedded within the clastic submarine fan suggest a fairly flat pattern with a moderate positive Eu anomaly and no La enrichment. We therefore suggest that the latter pattern typifies nonhydrothermal Archean seawater.Where seawater was influenced by a direct hydrothermal contribution, La enrichment and enhancement of the Eu anomaly could result. However, since periods of low-intensity discharge and (or) bottom-water mixing could eliminate the hydrothermal signal, not all samples from volcanic associations need show these features. By analogy with the Red Sea, preservation of a hydrothermal signal is most likely where circulation in the depositional basin is restricted and bottom waters are strongly reducing. Evidence for such conditions in the volcanic association is provided by the nature of the associated sediments (e.g., carbonaceous slates and unreworked distal turbidites).

Rare earth elements in volcanic rocks associated with Cu–Zn massive sulphide mineralization: a preliminary report

1982 ◽  
Vol 19 (3) ◽  
pp. 619-623 ◽  
Author(s):  
I. H. Campbell ◽  
P. Coad ◽  
J. M. Franklin ◽  
M. P. Gorton ◽  
S. D. Scott ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Massive Sulphide ◽  
Genetic History ◽  
Felsic Volcanism ◽  
Preliminary Study ◽  
Selection For ◽  
Felsic Volcanic ◽  
High Degree ◽  
Ree Patterns ◽  
Felsic Volcanic Rocks

Massive sulphide deposits are closely associated with felsic volcanism. This association is believed to be genetic and it forms the cornerstone for most exploration programs, but unfortunately not all felsic volcanic rocks contain ore. It seems likely that ore-bearing felsic volcanic rocks have a different genetic history from those that are barren and, if this is so, these differences should be reflected in their REE geochemistry.A preliminary study of REE in Archean felsic volcanic rocks has shown that those associated with ore have flat REE patterns with well-developed Eu anomalies whereas those from barren volcanic rocks have steep REE patterns with weak or absent Eu anomalies. The felsic volcanic rocks associated with ore can be subdivided into two types: tholeiitic and calc-alkaline. Kam-Kotia, Matagami, and South Bay are tholeiitic whereas Sturgeon Lake, Golden Grove, and Kuroko are calc-alkaline.The well-developed Eu anomalies in the ore-related felsic volcanic rocks indicate that the melt has undergone a high degree of fractional crystallization en route to the surface, suggesting the existence of a subvolcanic magma chamber below the orebody. The characteristic REE patterns of the ore-associated felsic volcanics should help mining companies in area selection for massive sulphide exploration.

Sulphur isotope composition of the Brunswick No. 12 massive sulphide deposit, Bathurst Mining Camp, New Brunswick: implications for ambient environment, sulphur source, and ore genesis

1996 ◽  
Vol 33 (2) ◽  
pp. 231-251 ◽  
Author(s):  
Wayne D. Goodfellow ◽  
Jan M. Peter
Keyword(s):  
Isotope Composition ◽  
Sedimentary Rocks ◽  
Massive Sulphide ◽  
Massive Sulphide Deposit ◽  
Bacterial Reduction ◽  
Sulphide Deposit ◽  
Sulphur Isotope ◽  
Middle Ordovician ◽  
Bathurst Mining Camp ◽  
Back Arc

The Brunswick No. 12 massive sulphide deposit occurs within a Middle Ordovician bimodal volcanic and sedimentary sequence that is thought to have formed in a continental back-arc rift covered with a thick succession of carbonaceous hemipelagic and turbiditic sedimentary rocks. The deposit consists of three en echelon lenses that are zoned from Vent Complex to Bedded Ore and Bedded pyrite facies. The Bedded Ore facies has the lowest average δ34S values (14.2[Formula: see text]), but are only slightly less positive than laminated pyrite in footwall sedimentary rocks (δ34Smean = 15.1[Formula: see text]). δ34S values for the bedded sulphides show an upward increase from 14.2[Formula: see text] in Bedded Ore to 16.5[Formula: see text] in Bedded Pyrite. Average δ34S values for Vent Complex (15.8[Formula: see text]) and underlying stringer sulphides (16.1[Formula: see text]) are consistently more positive than those for Bedded Ore. In carbonaceous shales and siltstone of the Patrick Brook Formation that underlie the deposit, δ34S values that range between 13.8 and 25.6[Formula: see text], and the similarity of these values to those of the Brunswick No. 12 deposit indicate major bacterial reduction of sulphate to sulphide under closed or partly closed conditions, and that most of the S in the deposit originated from ambient sulphidic bottom waters. Furthermore, the average δ34S value for Brunswick No. 12 bedded ores lies on the Selwyn Basin pyrite evolutionary curve and indicates that anoxic conditions within the Tetagouche back-arc basin reflect a global anoxic episode. The Brunswick No. 12 deposit probably formed, therefore, by the mixing of hydrothermal metals with dissolved sulphide of seawater origin during periods of ocean anoxia. The increase of δ34S values towards the Vent Complex may reflect the addition of isotopically heavy S formed by the inorganic reduction of seawater sulphate.

scholarly journals Petrology and rare earth element geochemistry of clastic metasedimentary rocks from the Isua supracrustal belt, West Greenland

1983 ◽  
Vol 112 ◽  
pp. 23-33
Author(s):  
J.L Boak ◽  
R.F Dymek ◽  
L.P Gromet
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Thermal Gradients ◽  
Element Geochemistry ◽  
Metasedimentary Rocks ◽  
Sediment Types ◽  
Supracrustal Belt ◽  
Shallow Basin ◽  
Ree Patterns

An investigation of the petrology and rare-earth element (REE) geochemistry of clastic metasedimentary rocks from the ~ 3800 Ma Isua Supracrustal Belt has been carried out to provide constraints on the nature of early Archaean metamorphie regimes and on the sources of their sedimentary protolith. The assemblages garnet + staurolite + biotite and biotite + kyanite (both with qtz + muse + plag + Hm) characterize the Isua metasediments and represent types common in younger metamorphic belts. Secondary chlorite and sericite occur in most samples. Garnet-biotite geothermometry indicates T = 541 ± 43°C for prograde metamorphism and T = 464 ± 39°C for retrograde metamorphism. Suggested metamorphic conditions of T - 550°C and P - 5 Kb imply burial to at least 15 Km with metamorphic thermal gradients < 40°C/Km. These data argue against excessively steep early Archaean crustal thermal gradients. REE patterns for three museovite-biotite gneisses are strongly fractionated (CeN = 40-100; YbN = 2-8) with variable Eu-anomalies (Eu/Eu* = 0.48-0.95), not unlike patterns for Arehaean felsic voicanic rocks in other areas. Garnet-biotite sehists have less-fractionated light REE, and exhibit a slope reversal for the heavy REE (i.e., GdN< YbN. These most plausibly represent a mixed felsic-mafic (- ultramafic?) protolith. Both sediment types could be the erosion produets of a rapidly emergent voicanic structure shedding debris into a shallow basin.

Trace element geochemistry of the Sokoman Iron Formation

1977 ◽  
Vol 14 (7) ◽  
pp. 1598-1610 ◽  
Author(s):  
B. J. Fryer
Keyword(s):  
Trace Element ◽  
Sea Water ◽  
Iron Formation ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Element Abundances ◽  
Rock Types ◽  
Show Evidence ◽  
Trace Element Contents ◽  
Element Contents

Rare earth and other trace element data are presented for samples of the Sokoman Iron Formation, Labrador, and its associated sediments. The results show that the slates associated with the iron formation are typical in trace element contents compared to other argillaceous sediments except for the large Eu depletion characteristic of slates of their age. The iron formation, however, is fundamentally different in its trace element concentrations and patterns from those of the associated rocks. It is relatively enriched in the heavy REE and Eu and both the REE and Co, Cr, Sc, and Th concentrations bear no relationship to those of the slates and the dolomite.Trace element analyses of the various textural and mineralogic rock types in all cases substantiate the genetic conclusions of earlier workers based on field and petrographic observations. Silicate–carbonate facies samples show constant REE, Co, Sc, and Th distributions which are compatible with an origin as crystalline precipitates in equilibrium with sea water. Riebeckite-bearing iron formation is distinctive in that it reflects contamination by ordinary clastic material and (or) metamorphic solutions. Oxide facies rocks exhibit widely variable trace element abundances as is to be expected for rocks whose original trace element contents were controlled by adsorption processes. A group of iron-enriched oxide facies rocks show evidence of important heavy REE complexing associated with the migration of iron during diagenesis. Minor Ce anomalies in all facies of Sokoman Iron Formation indicate that oxidation of Ce to the +4 state was taking place at the time of iron deposition but probably not in close proximity to it.

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