Eruptive Stratigraphy of the Tatara-San Pedro Complex, 36degreesS, Southern Volcanic Zone, Chilean Andes: Reconstruction Method and Implications for Magma Evolution at Long-lived Arc Volcanic Centers

Dungan, M. A.; Wulff, Andrew; Thompson, Ren A.

doi:10.1093/petrology/42.3.555

Cited by 136 publications

(87 citation statements)

References 91 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Volcanism at this complex features lavas ranging from primitive basalt to high silica rhyolites, with basaltic andesitic lavas being the most common product (Singer et al 1997;Dungan et al 2001). It comprises eight or more volcanic sequences (Dungan et al 2001) and at least three central vents regions (Singer et al 1997) during 930 ky of activity. San Pedro volcano is the youngest of the TSP complex, with basaltic to dacitic eruptive activity during the Holocene.…”

Section: Geological Contextmentioning

confidence: 99%

Regional electrical structure of the Andean subduction zone in central Chile (35°–36°S) using magnetotellurics

Reyes-Wagner

Díaz

Cordell

et al. 2017

Earth Planets Space

View full text Add to dashboard Cite

A profile of broadband magnetotelluric stations was acquired between 2009 and 2016 at 35°-36°S in the Southern Volcanic Zone of the Chilean Andes to image the subduction zone and its relation with the volcanic arc at this latitude. This transect extends from the Coastal Cordillera across the Central Valley and the volcanic arc of the Principal Cordillera to the Argentine border. Two active volcanic complexes are found along this profile: Tatara-San Pedro is located on the modern volcanic front, and the Laguna del Maule volcanic field is found approximately 30 km to the east. The latter exhibits considerable signs of unrest, such as uplift rates of up to 25 cm/year, and has produced a high concentration of silicic eruptions in the last 25 ky. The data covered the period range from 0.001 to 1000 s. Robust processing techniques were used, including remote reference, and dimensionality was investigated by estimation of geoelectric strike, skew and analysis of the induction arrows. The data were modeled using a 2D inversion algorithm to produce a resistivity model which was consistent with surface geology and seismicity. The final resistivity model shows a generally resistive fore-arc structure, coincident with the tectonic environment, and a wide conductive region from the volcanic front to the east. This suggests a broad region of magmatism throughout the arc, related to three distinct magma bodies, associated with the Tatara-San Pedro and Laguna del Maule volcanic complexes and the Mariposa Geothermal System.

show abstract

Section: Geological Contextmentioning

confidence: 99%

Regional electrical structure of the Andean subduction zone in central Chile (35°–36°S) using magnetotellurics

Reyes-Wagner

Díaz

Cordell

et al. 2017

Earth Planets Space

View full text Add to dashboard Cite

show abstract

“…The magmatic arc is characterized by a series of well spaced stratovolcanoes of andesitic to basaltic composition (López and Escobar 1984;Dungan et al 2001). The character of the arc magmatism is relatively less evolved than the typical compressional setting of the Central Andes, mainly due to its tectonic controlled setting.…”

Section: Strike-slip Regimesmentioning

confidence: 99%

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Ramos¹

2009

Geological Journal

227

139

View full text Add to dashboard Cite

The analyses of the main parameters controlling the present Chile-type and Marianas-type tectonic settings developed along the eastern Pacific region show four different tectonic regimes: (1) a nearly neutral regime in the Oregon subduction zone; (2) major extensional regimes as the Nicaragua subduction zone developed in continental crust; (3) a Marianas setting in the Sandwich subduction zone with ocean floored back-arc basin with a unique west-dipping subduction zone and (4) the classic and dominant Chile-type under compression. The magmatic, structural and sedimentary behaviours of these four settings are discussed to understand the past tectonic regimes in the Mesozoic Andes based on their present geological and tectonic characteristics. The evaluation of the different parameters that governed the past and present tectonic regimes indicates that absolute motion of the upper plate relative to the hotspot frame and the consequent trench roll-back velocity are the first order parameters that control the deformation. Locally, the influences of the trench fill, linked to the dominant climate in the forearc, and the age of the subducted oceanic crust, have secondary roles. Ridge collisions of seismic and seismic oceanic ridges as well as fracture zone collisions have also a local outcome, and may produce an increase in coupling that reinforces compressional deformation. Local strain variations in the past and present Andes are not related with changes in the relative convergence rate, which is less important than the absolute motion relative to the Pacific hotspot frame, or changes in the thermal state of the upper plate. Changes in the slab dip, mainly those linked to steepening subduction zones, produce significant variations in the thermal state, that are important to generate extreme deformation in the foreland.

show abstract

“…Rapid changes in bulkrock chemistry suggest that no significant magma chamber was established at this stage (Dungan et al 2001). Some 1.2 million years after initiation of extrusive activity, a continuous compositional evolution of subvolcanic intrusions with time is taken as evidence for the gradual build-up and growth of a subvolcanic magma chamber heated by continued advection of magma through the center of the volcano.…”

Section: Emplacement Of Intrusive and Extrusive Rocksmentioning

confidence: 99%

Magma evolution and the formation of porphyry Cu?Au ore fluids: evidence from silicate and sulfide melt inclusions

2005

View full text Add to dashboard Cite

Silicate and sulfide melt inclusions from the andesitic Farallo´n Negro Volcanic Complex in NW Argentina were analyzed by laser ablation ICPMS to track the behavior of Cu and Au during magma evolution, and to identify the processes in the source of fluids responsible for porphyry-Cu-Au mineralization at the 600 Mt Bajo de la Alumbrera deposit. The combination of silicate and sulfide melt inclusion data with previously published geological and geochemical information indicates that the source of ore metals and water was a mantle-derived mafic magma that contained approximately 6 wt.% H 2 O and 200 ppm Cu. This magma and a rhyodacitic magma mixed in an upper-crustal magma chamber, feeding the volcanic systems and associated subvolcanic intrusions over 2.6 million years. Generation of the ore fluid from this magma occurred towards the end of this protracted evolution and probably involved six important steps: (1) Generation of a sulfide melt upon magma mixing in some parts of the magma chamber. (2) Partitioning of Cu and Au into the sulfide melt (enrichment factor of 10,000 for Cu) leading to Cu and Au concentrations of several wt.% or ppm, respectively. (3) A change in the tectonic regime from local extension to compression at the end of protracted volcanism. (4) Intrusion of a dacitic magma stock from the upper part of the layered magma chamber. (5) Volatile exsolution and resorption of the sulfide melt from the lower and more mafic parts of the magma chamber, generating a fluid with a Cu/Au ratio equal to that of the precursor sulfide. (6) Focused fluid transport and precipitation of the two metals in the porphyry, yielding an ore body containing Au and Cu in the proportions dictated by the magmatic fluid source. The Cu/S ratio in the sulfide melt inclusions requires that approximately 4,000 ppm sulfur is extracted from the andesitic magma upon mixing. This exceeds the solubility of sulfide or sulfate in either of the silicate melts and implies an additional source for S. The extra sulfur could be added in the form of anhydrite phenocrysts present in the rhyodacitic magma. It appears, thus, that unusually sulfur-rich, not Cu-rich magmas are the key to the formation of porphyry-type ore deposits. Our observations imply that dacitic intrusions hosting the porphyryCu-Au mineralization are not representative of the magma from which the ore-fluid exsolved. The source of the ore fluid is the underlying more mafic magma, and unaltered andesitic dikes emplaced immediately after ore formation are more likely to represent the magma from which the fluids were generated. At Alumbrera, these andesitic dikes carry relicts of the sulfide melt as inclusions in amphibole. Sulfide inclusions in similar dykes of other, less explored magmatic complexes may be used to predict the Au/Cu ratio of potential ore-forming fluids and the expected metal ratio in any undiscovered porphyry deposit.

show abstract

Eruptive Stratigraphy of the Tatara-San Pedro Complex, 36degreesS, Southern Volcanic Zone, Chilean Andes: Reconstruction Method and Implications for Magma Evolution at Long-lived Arc Volcanic Centers

Cited by 136 publications

References 91 publications

Regional electrical structure of the Andean subduction zone in central Chile (35°–36°S) using magnetotellurics

Regional electrical structure of the Andean subduction zone in central Chile (35°–36°S) using magnetotellurics

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Magma evolution and the formation of porphyry Cu?Au ore fluids: evidence from silicate and sulfide melt inclusions

Contact Info

Product

Resources

About