Tertiary Tilting and Dismemberment of the Laramide Arc and Related Hydrothermal Systems, Sierrita Mountains, Arizona

Stavast, William J. A.; Butler, Robert F.; Seedorff, Eric; Barton, Mark D.; Ferguson, C.A.

doi:10.2113/gsecongeo.103.3.629

Cited by 22 publications

(10 citation statements)

References 15 publications

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“…Low volumes of erupted magma, and extensive associated hydrothermal alteration, suggest large volumes of magma remained in the crust where they crystallized as plutonic rocks. Similar situations have been observed in crustal sections exposed in tilted and eroded porphyry copper deposits (Dilles, 1987;Stavast et al, 2008). Extensive quartzalunite alteration in the eastern part of the Yanacocha district was centered on volcanic vent areas during several relatively short and discrete periods lacking volcanism (Figs.…”

Section: Magmatism and Oressupporting

confidence: 77%

Evolution of Calc-Alkaline Volcanism and Associated Hydrothermal Gold Deposits at Yanacocha, Peru

Longo¹,

Dilles²,

Grunder³

et al. 2010

Economic Geology

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Clusters of high-sulfidation epithermal deposits containing more than 50 Moz of gold are hosted by advanced argillic-altered Miocene volcanic rocks in the Yanacocha district, northern Peru (lat. 6°59'30" S, long. 78°30'45" W). We describe the nature of the volcanism and its relation to the gold ores on the basis of new district-scale geologic mapping, 69 40 Ar/ 39 Ar ages on igneous rocks and hydrothermal alunite, and petrologic and geochemical investigations. Volcanic rocks of the Calipuy Group are the oldest Cenozoic rocks at Yanacocha, and include the Huambo Cancha andesite, andesitic lahars of Tual and Chaupiloma (19.5-15.9 Ma), and the dacitic Cerro Fraile pyroclastics (15.5-15.1 Ma). The younger Yanacocha Volcanics (14.5-8.4 Ma) form a cogenetic series of lavas and pyroclastic rocks with a cumulative volume of ~88 km 3 that represents eruption from a moderate-size volcanic center. Early pyroxene>hornblende-bearing lavas of the Atazaico Andesite (14.5-13.3 Ma) erupted from small stratovolcanoes progressively younger from southwest to northeast. Dacitic dikes followed that are spatially associated with gold deposits at Quilish and Cerro Negro (~7 Moz Au) and stage 1 alunite (13.6-12.6 Ma). The Colorado Pyroclastics erupted in the center of the district and include the hornblende-and biotite-bearing andesitic to dacitic Cori Coshpa (12.6 Ma) and Maqui Maqui (12.5-12.4 Ma) ignimbrites. The Colorado Pyroclastics are overlain by hornblende>pyroxene-bearing andesitic to dacitic lavas, flow-domes, and minor pyroclastic rocks of the Azufre Andesite (12.1-11.6 Ma). Widespread stage 2 alunite (11.5 Ma) and minor gold deposition (~0.5 Moz) closely follow. The San Jose Ignimbrite (11.5-11.2 Ma) overlies the Azufre Andesite and stage 2 alunite and includes three members of hornblende-pyroxene (biotite) dacite and andesite that erupted in the center of the district and flowed southward. Mineralogically similar domes were emplaced into the inferred vents. The Coriwachay Dacite (10.8-8.4 Ma) forms the youngest and most silica rich igneous rocks in the district, and includes intrusions and flow domes of dacite to rhyolite at Corimayo (10.8 Ma), Cerro Yanacocha (9.9 Ma), and Yanacocha Lake (8.4 Ma). Most of the gold (>47 Moz) was deposited at Yanacocha during intrusion of the late Coriwachay Dacite. These late dacites are volumetrically smallest (~2% of the total volume of erupted magma) and are temporally associated with stage 3 to 5 alunites. Stage 3 alunite (11.0-10.7 Ma) developed along a northeast trend for 9 km that includes the gold deposits of Corimayo, San Jose, Carachugo, and Maqui Maqui. The deeper Kupfertal Cu-Au porphyry has an age of 10.7 Ma on hydrothermal biotite and underlies zones of stage 4 and 5 quartz-alunite alternation that are 0.8 and 1.5 m.y. younger, respectively. Stage 4 alunite ranges in age from 10.2 to 10.3 Ma at the Tapado and Chaquicocha Sur gold deposits to Cerro Sugares east of the Maqui Maqui deposit. Stage 4 also includes a younger alunite age of 9.9 Ma from the San Jose gold deposit. Stage...

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Section: Magmatism and Oressupporting

confidence: 77%

Evolution of Calc-Alkaline Volcanism and Associated Hydrothermal Gold Deposits at Yanacocha, Peru

Longo¹,

Dilles²,

Grunder³

et al. 2010

Economic Geology

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“…Eventually, Wilkins and Heidrick (1995) suggested that all porphyry deposits in the Basin and Range province should be assumed to be faulted and tilted until proven otherwise. During the past decade, the importance of tilting of orebodies across the Basin and Range province has continued to be emphasized (e.g., Seedorff et al, 2005a, p. 276-277;Maher, 2008;Stavast et al, 2008;Nickerson et al, 2010) and is again demonstrated here.…”

Section: Exploration Targetssupporting

confidence: 54%

“…1). However, few previous investigations consider the effect that postmineralization normal faulting has had on spatial relationships at the deposit or district scale (e.g., Lowell, 1968;Wilkins and Heidrick, 1995;Wodzicki, 1995;Stavast et al, 2008), and especially at the scale of the magmatic arc (Richard, 1994;Staude and Barton, 2001).…”

Section: Introductionmentioning

confidence: 99%

Dismembered Porphyry Systems near Wickenburg, Arizona: District-Scale Reconstruction with an Arc-Scale Context

Nickerson¹,

Seedorff²

2016

Economic Geology

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This study combines results from reconnaissance-scale mapping of hydrothermal alteration, rock types, and structures to provide a district-scale cross section and associated palinspastic reconstruction of an area with two previously undescribed Laramide (~70 Ma) porphyry systems at Sheep Mountain and Copper Basin (Crown King). Extension at the district scale is placed in an arc-scale context using an original compilation of strike and dip measurements on Tertiary rocks to reconstruct the Laramide porphyry belt prior to extension. The study area contains five sequential, partially superimposed sets of normal faults that are nearly planar where exposed. Dips of all normal faults initiated at 60° to 70° and rotated during slip to angles as gentle as 20°. A palinspastic reconstruction reveals that two, spatially distinct hydrothermal systems overlie different cupolas of a Late Cretaceous pluton. Hydrothermal alteration is zoned from greisen to potassic to transitional greisenpotassic assemblages from deep to shallow structural levels. The reconstruction is used to identify two covered exploration targets. The prospects may be porphyry molybdenum systems of the quartz monzonitic-granitic porphyry Mo-Cu subclass, joining others in an arc that is best known for porphyry copper deposits. The Laramide porphyry belt prior to extension displays a variably well-defined axis, ~100 km wide, with gaps and clusters of deposits along its 700-km strike length. The majority of deposits lie along the axis, but others lie in fore-or rear-arc positions. The interpreted preextensional geometry of the Laramide porphyry belt resembles other porphyry belts and the distribution of active volcanoes at convergent margins.

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“…12d-f), which is typical for plutons underlying porphyry systems (e.g. Dilles, 1987;Cloos, 2001;Stavast et al, 2008;Sillitoe, 2010;Steinberger et al, 2013). At such pressures a silicic melt is water saturated at 5 6 1 wt % ( Fig.…”

Section: The Porphyriesmentioning

confidence: 88%

Petrological Evolution of the Magmatic Suite Associated with the Coroccohuayco Cu(–Au–Fe) Porphyry–Skarn Deposit, Peru

et al. 2015

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The petrological evolution of magmatic rocks associated with porphyry-related Cu deposits is thought to exert a first-order control on ore genesis. It is therefore critical to understand and recognize petrological processes favourable to the genesis of porphyry systems. In this study we present new petrographic, geochemical (whole-rock and mineral), and isotopic (Pb, Sr, Nd) data for rocks from the magmatic suite associated with the Eocene Coroccohuayco porphyry-skarn deposit, southern Peru. Previously determined radiometric ages on these rocks provide the temporal framework for interpretation of the data. Arc-style magmatic activity started at Coroccohuayco with the emplacement of a composite precursor gabbrodiorite complex at c. 40Á4 Ma. After a nearly 5 Myr lull, magmatic activity resumed at c. 35Á6 Ma with the rapid emplacement of three dacitic porphyries associated with mineralization. However, zircon antecrysts in the porphyries show that intra-crustal magmatic activity started c. 2 Myr before porphyry emplacement and probably built a large intracrustal magmatic body with an associated large thermal anomaly. Our data suggest that all magmas underwent a period of evolution in the deep crust before transfer and further evolution in the upper crust. The gabbrodiorite complex was sourced from a heterogeneous deep crustal reservoir and was emplaced at a pressure of 100-250 MPa where it underwent a limited amount of fractionation and formed a chemically zoned pluton. Its initial water content and oxygen fugacity were estimated to be around 3 wt % H 2 O and NNO 6 1 (where NNO is the nickel-nickel oxide buffer), respectively. The deep crustal source of the porphyries appears to have been more homogeneous. The porphyries are interpreted to be the product of advanced differentiation of a parental magma similar to the gabbrodiorite. Most of this evolution occurred at deep crustal levels (around 800 MPa) through fractionation of amphibole þ pyroxene þ plagioclase 6 garnet, leading to the development of a high Sr/Y signature characteristic of porphyry-related magmatism worldwide. Subsequent upper crustal evolution (100-250 MPa) was dominated by crustal assimilation, cannibalism of previously emplaced magma batches (proto-plutons) and magma recharge. Water content and oxygen fugacity were estimated to be around 5 wt % H 2 O and NNO þ 1 to NNO þ 2, respectively, at the end of the period of upper crustal evolution. This high oxygen fugacity is inferred to have favoured sulphur and metal enrichment in the melt. The high thermal regime generated through 2 Myr of sustained magmatism in the upper crust favoured crustal assimilation, proto-pluton cannibalism, and efficient metal extraction upon fluid exsolution. The Coroccohuayco magmatic suite appears to have acquired its metallogenic potential (high fO 2 , high Sr/Y) through several million years of deep crustal evolution.

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Tertiary Tilting and Dismemberment of the Laramide Arc and Related Hydrothermal Systems, Sierrita Mountains, Arizona

Cited by 22 publications

References 15 publications

Evolution of Calc-Alkaline Volcanism and Associated Hydrothermal Gold Deposits at Yanacocha, Peru

Evolution of Calc-Alkaline Volcanism and Associated Hydrothermal Gold Deposits at Yanacocha, Peru

Dismembered Porphyry Systems near Wickenburg, Arizona: District-Scale Reconstruction with an Arc-Scale Context

Petrological Evolution of the Magmatic Suite Associated with the Coroccohuayco Cu(–Au–Fe) Porphyry–Skarn Deposit, Peru

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