Characteristics and occurrence of bedding-parallel slip surfaces and laminated veins in chevron folds from the Bendigo-Castlemaine goldfields: implications for flexural-slip folding

Fowler, T.J.; Winsor, C.N.

doi:10.1016/s0191-8141(97)00004-7

Cited by 31 publications

(14 citation statements)

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“…Several large and rich bodies occur in the flexures of folds, including the Mercedes-Chocayoc orebody. They are comparable structurally to saddle-reef structures described in some vein deposits (e.g., Bendigo, Australia; e.g., Fowler and Winsor, 1997). This style of mineralization, controlled by bedding openings that result from flexure, is a typical feature of mineralization that postdates folding.…”

Section: Discussion and Interpretationsupporting

confidence: 71%

Cordilleran Epithermal Cu-Zn-Pb-(Au-Ag) Mineralization in the Colquijirca District, Central Peru: Deposit-Scale Mineralogical Patterns

Bendezu¹,

Fontboté²

2009

Economic Geology

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Abstract0361-0128/09/3845/905-40 905 Introduction PERU is a major producer of silver, copper, zinc, lead, bismuth, tin, and gold. Of these metals, zinc, lead, silver, tin, and bismuth are produced dominantly from deposits of several styles but all sharing the following major features: (1) polymetallic (Cu-Zn-Pb-Ag-Au) suite; (2) zoned from inner Cu-bearing to outer Zn-Pb−bearing ores; (3) sulfide-rich character, commonly massive; and (4) primary occurrence as open-space fillings (veins, breccia bodies) in silicate host rocks and as replacements in carbonate rocks. Sawkins (1972) classified ores displaying these features as Cordilleran vein-type deposits. Later, Einaudi (1982) described these deposits as Cordilleran vein or lode deposits within the context of porphyry-related systems. Additional general discussions on Cordilleran vein deposits are given by Guilbert and Park (1986), Bartos (1989), andBendezú (2009). Recently, this type of mineralization has been termed "zoned base metal veins" by Einaudi et al. (2003); however, a clear zonation is not always recognized, and the ores in many districts are dominantly mantos and not veins, and they commonly contain Au and Ag in addition to base metals. We therefore prefer the more general term "Cordilleran polymetallic deposits" Fontboté and Bendezú, 2009 AbstractAt Colquijirca, central Peru, a Miocene diatreme-dome complex is associated in space and time with several large epithermal polymetallic (Cu-Zn-Pb-Au-Ag) deposits of the Cordilleran class. Of these deposits, Smelter and Colquijirca, located in the northern sector of the district, are part of a continuously mineralized northsouth corridor that extends for nearly 4 km outward from the diatreme-dome complex and to depths of 1 km below surface. This corridor is zoned from Cu-(Au) ores in its inner parts (Smelter deposit) to peripheral ZnPb-(Ag) ores (Colquijirca deposit). The Smelter-Colquijirca corridor has undergone minor erosion, providing a good example of a nearly intact paleo-epithermal system of the Cordilleran class.This description of the hypogene mineralogical patterns of the Smelter-Colquijirca corridor leads to the proposal that they are the result of superimposition in time and space of three main stages. During an early quartzpyrite stage, in which basically no economic ore deposition occurred, carbonate rocks surrounding the Marcapunta diatreme-dome complex were replaced by quartz and pyrite. This was followed by the main ore stage, which was largely superimposed on the quartz-pyrite replacements and produced zonation of ore minerals and metals along much of the Smelter-Colquijirca corridor. The zoning from Cu ores to Zn-Pb ores is complex and comprises a number of distinct and well-defined zones that display abrupt or gradual interfaces between zones. From internal to external parts, these zones consist mainly of the following mineral associations and assemblages: (1) enargite ± (luzonite, pyrite, colusite, tennantite, goldfieldite, ferberite, gold-silver tellurides, bismuthinite, gold, alunite,...

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Section: Discussion and Interpretationsupporting

confidence: 71%

Cordilleran Epithermal Cu-Zn-Pb-(Au-Ag) Mineralization in the Colquijirca District, Central Peru: Deposit-Scale Mineralogical Patterns

Bendezu¹,

Fontboté²

2009

Economic Geology

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“…A similar evolution has been widely hypothesized for outcrop-scale buckle folds on the basis of theory, models, and observation (e.g., De Sitter, 1956;Ramsay, 1967;Behzadi and Dubey, 1980;Ramsay and Huber, 1987;Gray and Wilman, 1991;Bhattacharya, 1992;Yang and Gray, 1994;Fowler and Winsor, 1997). However, the concept has not been widely recognized to apply to map-scale folds, where geometry and strain are difficult to quantify precisely at the scale of an entire fold, and where a very complex multi-layered mechanical stratigraphy is typical.…”

Section: Preliminary Model For Northeastern Brooks Range Detachment Fsupporting

confidence: 73%

The Influence of Fold and Fracture Development on Reservoir Behavior of the Lisburne Group of Northern Alaska

Wallace¹,

Hanks²,

Whalen³

et al. 2000

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The Lisburne Group is a major carbonate reservoir unit in northern Alaska. The Lisburne is detachment folded where it is exposed throughout the northeastern Brooks Range, but is relatively undeformed in areas of current production in the subsurface of the North Slope. The objectives of this study are to develop a better understanding of four major aspects of the Lisburne:1. The geometry and kinematics of detachment folds and their truncation by thrust faults. 2. The influence of folding and lithostratigraphy on fracture patterns. 3. Lithostratigraphy and its influence on folding, faulting, fracturing, and reservoir characteristics.4. The influence of lithostratigraphy and deformation on fluid flow. The results of field work during the summer of 1999 offer some preliminary insights:The Lisburne Limestone displays a range of symmetrical detachment fold geometries throughout the northeastern Brooks Range. The variation in fold geometry suggests a generalized progression in fold geometry with increasing shortening: Straight-limbed, narrow-crested folds at low shortening, box folds at intermediate shortening, and folds with a large height-to-width ratio and thickened hinges at high shortening. This sequence is interpreted to represent a progressive change in the dominant shortening mechanism from flexural-slip at low shortening to bulk strain at higher shortening. Structural variations in bed thickness occur throughout this progression. Parasitic folding accommodates structural thickening at low shortening and is gradually succeeded by penetrative strain as shortening increases. The amount of structural thickening at low to intermediate shortening may be inversely related to the local amount of structural thickening of the Kayak Shale, the incompetent unit that underlies the Lisburne.The Lisburne Limestone displays a different structural style in the south, across the boundary between the northeastern Brooks Range and the main axis of the Brooks Range fold-and-thrust belt. The steep forelimbs of angular asymmetrical folds typically have been cut and displaced by thrust faults, resulting in superposition of a fault-bend fold geometry on the truncated folds. Remnant uncut folds within trains of thrust-truncated folds and the predominance of detachment folds to the north suggest that these folds originated as detachment folds. Fold asymmetry and a more uniformly competent Lisburne Limestone may have favored accommodation of a significant proportion of shortening by thrust faulting, in contrast with the dominance of fold shortening to the north.Two dominant sets of fractures are present in the least deformed Lisburne Limestone: Early extension fractures normal to the regional fold trend and late extension and shear fractures parallel to the regional fold trend. These two major fracture sets remain as deformation increases, but they are more variable in orientation, character, and relative age. Compared to fold limbs, the fold hinges display greater density and extent of fractures, more conjugate and shear fractur...

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“…The internal structure of the Q-1b veins with several thin graphite-bearing wall-rock laminae, separated by interlocking quartz domains may have formed during repeated opening and sealing of the veins by recurrent and successive slip (cf. Fowler & Winsor 1997;Séjourné et al 2005). Passchier & Trouw (1996) proposed formation during alternating stages of growth and crystal-plastic deformation of Q-1b veins (antitaxial veins), typical for brittleductile shearing conditions.…”

Section: Gold Lodes and Deformationmentioning

confidence: 99%

Fluid evolution in the El-Sid gold deposit, Eastern Desert, Egypt

Zoheir

Moritz

2014

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Auriferous quartz (+carbonate) veins in the El-Sid mine cut through the western margin of the Fawakhir granitic intrusion and the immediate country ophiolites. Gold mineralization is spatially and temporally associated with ENE-WSW fault/shear zones developed late in the deformational history of the area. Field and microscopic studies suggest two distinct ore stages; namely an early gold-Fe-As-sulphide, and a late gold-base metal mineralization. New microthermometric and Raman data suggest gold deposition as a result of a complex history of fluid immiscibly, dilution of low-salinity aqueous-carbonic fluids in the early mineralization stage, while wall-rock alteration and pressure loss precipitated Au from intermediate-salinity aqueous ore fluids during the late stage. Fluid inclusion isochoric reconstructions, combined with oxygen and sulphur isotope data, indicate conditions of 320 + 20 8C and 1.3 + 0.2 kbar for the early gold-Fe-As-sulphide mineralization, and c. 200 + 15 and 0.6 + 0.9 kbar for the late gold-Zn-Pb-Cu-sulphide stage. The clockwise evolution path in pressure-temperature space likely documents gold mineralization under post-peak metamorphic conditions. The calculated sulphide d 34 S H2S equilibrium values 29.04‰ to -4.75‰, may refer to a variable redox state of sulphur in the ore fluids from the early to late mineralization stages. The stable isotope signature of the vein quartz and calcite suggest mixed magmatic and metamorphic fluid sources (d 18 O H2O ¼ +4.9‰ to +7.4‰). Unusually low d 13 C values of calcite in the late mineralization (213.9‰ to 214.7‰) may reflect input of magmatic CO 2 and/or oxidized carbonaceous material in the infiltrating fluid.

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Characteristics and occurrence of bedding-parallel slip surfaces and laminated veins in chevron folds from the Bendigo-Castlemaine goldfields: implications for flexural-slip folding

Cited by 31 publications

References 38 publications

Cordilleran Epithermal Cu-Zn-Pb-(Au-Ag) Mineralization in the Colquijirca District, Central Peru: Deposit-Scale Mineralogical Patterns

Cordilleran Epithermal Cu-Zn-Pb-(Au-Ag) Mineralization in the Colquijirca District, Central Peru: Deposit-Scale Mineralogical Patterns

The Influence of Fold and Fracture Development on Reservoir Behavior of the Lisburne Group of Northern Alaska

Fluid evolution in the El-Sid gold deposit, Eastern Desert, Egypt

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