Durchbewegung structure, piercement cusps, and piercement veins in massive sulfide deposits; formation and interpretation

Marshall, Brian D.; Gilligan, L.B.

doi:10.2113/gsecongeo.84.8.2311

Cited by 56 publications

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“…Fracturing is often considered to have occurred during continuing movements affecting the whole sulphide mass, which, at the temperatures prevailing, must have deformed in a ductile or plastic manner. Movement of this type, often involving rotation of the more brittle components of the ores (silicate fragments, pyrite and other porphyroblasts) in a matrix of the more ductile components, has been referred to by the German term Durchbewegung (Vokes, 1969(Vokes, , 1973Marshall and Gilligan, 1989). Evidence is often present that fracturing of pyrite metablasts was initiated where two or more of these impinged on each other during these rotational movements (See Fig.…”

Section: Microtextures Indicative Of Internal Mobilisationmentioning

confidence: 99%

Post-recrystallisation mobilisation phenomena in metamorphosed stratabound sulphide ores

Vokes

Craig

1993

Mineral. mag.

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Metamorphosed stratabound iron-and base-metal sulphide deposits often exhibit microtextures in which fractures in cataclastically-deformed pyrite porphyroblasts are filled with matrix sulphides; chalcopyrite, sphalerite, pyrrhotite or galena. Discussions of such textures have mostly centred on whether solid-phase or fluid-phase mechanisms were responsible for the movement of the matrix sulphides.The small Zn-Cu sulphide body at Gressli, in the central Norwegian Caledonides, shows these textural features to an extreme degree. Both chalcopyrite and sphalerite show heavy replacive relations to the cataclastically deformed metablastic pyrite, along fracture walls and grain boundaries. They also occur injected along the opened-up triple junctions of foam-textured pyrite. In addition, parts of the ore show patchy quartz with clear replacive relationship to all three sulphides, a feature not often reported from such ores. Such textures can be interpreted to support a mobilisation sequence chalcopyrite-sphalerite-quartz within the Gressli ore. Their extent and degree of development indicate that fluid-phase mobilisation of the three minerals must have played a dominant role. Chalcopyrite and sphalerite are most likely derived from within the ore-mass itself; an external source for the SiO2 seems most probable, in the form of metahydrothermal solutions moving along retrograde shear zones at or near ore-walls.

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Section: Microtextures Indicative Of Internal Mobilisationmentioning

confidence: 99%

Post-recrystallisation mobilisation phenomena in metamorphosed stratabound sulphide ores

Vokes

Craig

1993

Mineral. mag.

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“…The occurrence, and likely late remobilization, of chalcopyrite in high angle veins 401 relative to S 2 across the sulfide assemblages, is very common and expected in 402 durchbewegung structures (Marshall and Gilligan, 1989), and suggests that the late 403 chalcopyrite veins are a direct consequence of the structural evolution of the 404 durchbewegung structure hosting the Whalesback deposit. Close folding and boudinage 405 of Cu-rich ore (Fig.…”

Section: Sulfide Textural Evolution During Deformation and Remobilizamentioning

confidence: 95%

“…Durchbewegung textured rocks are generally hosted within durchbewegung 366 structures (Marshall and Gilligan, 1989), which form from the progression of folding and 367 shearing related to the formation of tight to isoclinal folds. In these structures, the silicate 368 layers surrounding the less competent sulfide layers become disrupted, detached and 369 incorporated into the sulfides as they deform ductily.…”

Section: Sulfide Textural Evolution During Deformation and Remobilizamentioning

confidence: 99%

“…In these structures, the silicate 368 layers surrounding the less competent sulfide layers become disrupted, detached and 369 incorporated into the sulfides as they deform ductily. This process results in the creation 370 of detached fold cores and boudins of varying geometry depending on competency 371 contrast between the silicate and sulfide layers (Marshall and Gilligan, 1989). Relatively 372 late piercement (or ductile) veins are commonly associated with the formation of 373 durchbewegung structures.…”

Section: Sulfide Textural Evolution During Deformation and Remobilizamentioning

confidence: 99%

“…Relatively 372 late piercement (or ductile) veins are commonly associated with the formation of 373 durchbewegung structures. The veins range in size from a few centimeters to a few 374 meters wide and generally form at high angle to the layer interface and fill in extensional 375 planar fractures (Marshall and Gilligan, 1989). 376…”

Section: Sulfide Textural Evolution During Deformation and Remobilizamentioning

confidence: 99%

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Styles, Textural Evolution, and Sulfur Isotope Systematics of Cu-Rich Sulfides from the Cambrian Whalesback Volcanogenic Massive Sulfide Deposit, Central Newfoundland, Canada

et al. 2015

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21The Whalesback Cu-rich VMS deposit in the Newfoundland Appalachians is a 22 highly deformed deposit found on a steep limb of a closed and boudinaged overturned 23 fold. The deposit was intensely deformed at low temperature but medium pressure (>175 24 MPa) during the accretion of the composite Lushs Bight Oceanic Tract-Dashwoods 25 terrane onto the Humber margin at ca. 480 Ma. 26The ore mineralogy consists of chalcopyrite, pyrrhotite and pyrite with lesser 27 sphalerite and trace Ag-, Bi-and Hg-tellurides. Four styles of sulfide mineralization are 28 present: 1) disseminated (5%); 2) vein (50%); 3) breccia (25%); and 4) semi-massive to 29 massive (20%). Independent of mineralization style, massive pyrite and pyrrhotite (and 30 some chalcopyrite) are commonly parallel to main S 2 schistosity in the deposit, whereas 31 late chalcopyrite piercement veins occur at a high angle to S 2 . The progressive increase in 32 pressure and temperature produced a remobilization sequence wherein sphalerite was the 33 first sulfide phase to cross the brittle-ductile boundary, followed by pyrrhotite and finally 34 chalcopyrite. Maximum temperature was not high enough for the pyrite to cross the 35 brittle-ductile boundary. Instead, pyrite grains were incorporated and transported by 36 pyrrhotite and chalcopyrite during the ductile remobilization events, rounding and 37 fracturing them. Remobilization of the sulfides occurred mainly by plastic flow, but some 38 solution transport and re-precipitation is locally observed. 39In situ secondary ion mass spectrometry (SIMS) sulfur isotopes geochemistry of 40 sulfides yielded values of δ 34 S ranging from +2.7‰ to 4.7‰ for pyrite, +2.1‰ to 4.0‰ 41 for pyrrhotite and +1.3‰ to 4.7‰ for chalcopyrite. Sulfur isotopic modeling suggests 42 3 that at least 60% of the sulfur was derived from leaching of igneous rocks (i.e., basalts), 43 with the reminder derived from thermochemical sulfate reduction (TSR) of seawater 44 sulfate during alteration of the basalts by seawater. At the deposit scale, sulfur isotopes 45 retained their original signature and did not re-equilibrate during the secondary 46 deformation and remobilization events. 47

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Formation mechanisms of oreshoots in massive sulphide orebodies at Hongtoushan, NE China

Xiaoqian

Yuanchuan

et al. 2005

Mineral Deposit Research: Meeting the Global Challenge

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Durchbewegung structure, piercement cusps, and piercement veins in massive sulfide deposits; formation and interpretation

Cited by 56 publications

References 0 publications

Post-recrystallisation mobilisation phenomena in metamorphosed stratabound sulphide ores

Post-recrystallisation mobilisation phenomena in metamorphosed stratabound sulphide ores

Styles, Textural Evolution, and Sulfur Isotope Systematics of Cu-Rich Sulfides from the Cambrian Whalesback Volcanogenic Massive Sulfide Deposit, Central Newfoundland, Canada

Formation mechanisms of oreshoots in massive sulphide orebodies at Hongtoushan, NE China

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