Petrologic diversity of Plio-Quaternary post-subduction volcanism in northwestern Mexico: An example from Isla San Esteban, Gulf of California

2008 ◽  
Vol 179 (5) ◽  
pp. 465-481 ◽  
Author(s):  
Thierry Calmus ◽  
Carlos Pallares ◽  
René C. Maury ◽  
Hervé Bellon ◽  
Efrén Pérez-Segura ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Thermal Flux ◽  
Lava Flows ◽  
Calc Alkaline ◽  
Pyroclastic Deposits ◽  
Extensional Tectonic ◽  
Tectonic Framework ◽  
Northwestern Mexico ◽  
Sketch Map ◽  
Slab Window

Abstract During the Plio-Quaternary, numerous volcanic centres of contrasted compositions were emplaced in the Baja California Peninsula and adjacent Gulf of California. The 43 km2 Isla San Esteban (28o 42 N and 112o 34’ W), located in the central part of the gulf near the Pliocene extinct spreading centre of Lower Tiburón basin, is mostly made of andesitic, dacitic and rhyolitic subaerial lava flows, domes, and pyroclastic deposits. A new geological sketch map of the island is presented, as well as new K-Ar ages ranging from 4.5 to 2.5 Ma. Isla San Esteban lavas belong to two nearly contemporaneous magmatic series emplaced within an extensional tectonic framework related to the continental breakoff followed by the progressive oceanization along the Gulf of California. The first one is medium-K calc-alkaline, and its magmas evolved from basaltic andesites to rhyolites by fractionation of plagioclase, pyroxenes, titanomagnetite and apatite. The second one includes genuine adakites, and dacites derived from them through separation of plagioclase plus amphibole. We propose that these adakites originated from the partial melting of oceanic crust slivers, incorporated to the subcontinental lithospheric mantle during the Late Miocene opening of a slab window followed by the detachment of the deep part of the Farallon slab. The high thermal flux linked to the opening of the Gulf would have triggered their melting, as well as that of the subduction-modified mantle, which represents the likely source of the associated calc-alkaline lavas.

Paleoclimate of the Gulf of California (Northwestern Mexico) During the Last 2000 Years

2019 ◽  
pp. 7-38
Author(s):  
Aída Martínez-López ◽  
Olivia de Los Ángeles Flores-Castillo ◽  
Romeo Saldívar-Lucio ◽  
Diana Cecilia Escobedo-Urías ◽  
Gerardo Verdugo-Díaz ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Northwestern Mexico

scholarly journals Development of Convective Systems over Baja California during Tropical Cyclone Linda (2003)

2005 ◽  
Vol 20 (5) ◽  
pp. 801-811 ◽  
Author(s):  
Luis M. Farfán
Keyword(s):  
Tropical Cyclone ◽  
Gulf Of California ◽  
Large Scale ◽  
Baja California ◽  
Precipitable Water ◽  
Sea Breeze ◽  
Convective Systems ◽  
Early Afternoon ◽  
Northwestern Mexico ◽  
Western Side

Abstract Characteristics of the life cycle and motion of convective systems that occurred over the Baja California Peninsula were determined from a case study in September of 2003. This note applies data from satellite imagery, regular observations from upper-air and surface networks, and operational analyses. Changes in environmental conditions over northwestern Mexico are documented and these are associated with the development of Tropical Cyclone Linda in the eastern Pacific Ocean. When Linda became a tropical storm and was located several hundred kilometers away to the southwest, a convective outbreak occurred over land. An examination of large-scale conditions indicated that flow from the eastern flank of Linda supplied low- to midlevel moisture. Significant convection is associated with specific thresholds for precipitable water, CAPE, and lifted index. Convective systems initiated in the early afternoon remained active for several hours and provided localized areas of precipitation along the western side of the peninsular mountains. An assessment of all the available surface data was performed to determine regional elements that played a role in the development of these systems. Results include documentation of a sea breeze from the Gulf of California onto the mountain slopes when organized convection was first detected.

The Westwood Deposit, Southern Abitibi Greenstone Belt, Canada: An Archean Au-Rich Polymetallic Magmatic-Hydrothermal System—Part I. Volcanic Architecture, Deformation, and Metamorphism

2021 ◽  
Author(s):  
D. Yergeau ◽  
P. Mercier-Langevin ◽  
B. Dubé ◽  
M. Malo ◽  
A. Savoie
Keyword(s):  
Fractional Crystallization ◽  
Greenstone Belt ◽  
Massive Sulfide ◽  
Hydrothermal Systems ◽  
Lava Flows ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
Intrusive Rocks ◽  
Ore Zones

Abstract The Westwood deposit (4.5 Moz Au) is hosted in the 2699–2695 Ma Bousquet Formation volcanic and intrusive rocks, in the eastern part of the Blake River Group, southern Abitibi greenstone belt. The Bousquet Formation is divided in two geochemically distinct members: a mafic to intermediate, tholeiitic to transitional lower member and an intermediate to felsic, transitional to calc-alkaline upper member. The Bousquet Formation is cut by the synvolcanic (2699–2696 Ma) polyphase Mooshla Intrusive Complex, which is cogenetic with the Bousquet Formation. The deposit contains three strongly deformed (D2 flattening and stretching), steeply S-dipping mineralized corridors that are stacked from north to south: Zone 2 Extension, North Corridor, and Westwood Corridor. The North and Westwood corridors are composed of Au-rich polymetallic sulfide veins and stratabound to stratiform disseminated to massive sulfide ore zones that are spatially and genetically associated with the calcalkaline, intermediate to felsic volcanic rocks of the upper Bousquet Formation. The formation of the disseminated to semimassive ore zones is interpreted as strongly controlled by the replacement of porous volcaniclastic rocks at the contact with more impermeable massive cap rocks that helped confine the upflow of mineralizing fluids. The massive sulfide lenses are spatially associated with dacitic to rhyolitic domes and are interpreted as being formed, at least in part, on the paleoseafloor. The epizonal, sulfide-quartz vein-type ore zones of the Zone 2 Extension are associated with the injection of subvolcanic, calc-alkaline felsic sills and dikes within the lower Bousquet Formation. These subvolcanic intrusive rocks, previously interpreted as lava flows, are cogenetic and coeval with the intermediate to felsic lava flows and domes of the upper Bousquet Formation. The change from fractional crystallization to assimilation- and fractional crystallization-dominated processes and transitional to calc-alkaline magmatism is interpreted to be responsible for the development of the auriferous ore-forming system. The Westwood deposit is similar to some Phanerozoic Au ± base metal-rich magmatic-hydrothermal systems, both in terms of local volcano-plutonic architecture and inferred petrogenetic context. The complex volcanic evolution of the host sequence at Westwood, combined with its proximity to a polyphase synvolcanic intrusive complex, led to the development of one of the few known large Archean subaqueous Au-rich magmatic-hydrothermal systems.

Drawing igneous outcrops

2019 ◽  
pp. 117-140
Author(s):  
Matthew J. Genge
Keyword(s):  
Summit Crater ◽  
Worked Examples ◽  
Igneous Rocks ◽  
Lava Flows ◽  
Mount Etna ◽  
Pyroclastic Deposits ◽  
Fundamental Component ◽  
The Earth

Igneous rocks are a fundamental component of the Earth and are commonly encountered during geological fieldwork. This chapter describes techniques used to draw field sketches of intrusions and volcanic features, such as lava flows, volcanic craters, and pyroclastic sequences. The most important features of igneous rocks to record are discussed. Recording the nature of contacts is particularly important in drawing igneous outcrops, in particular cross-cutting relationships that relate to emplacement timing. Four worked examples of field sketches of igneous geology are provided to illustrate concepts in their description in during fieldwork. These include the summit crater of Vesuvius, lava flows from Mount Etna, and pyroclastic deposits from Santorini.

Does slab-window opening cause uplift of the overriding plate? A case study from the Gulf of California

2017 ◽  
Vol 719-720 ◽  
pp. 162-175 ◽  
Author(s):  
Chris Mark ◽  
David Chew ◽  
Sanjeev Gupta
Keyword(s):  
Gulf Of California ◽  
Window Opening ◽  
Slab Window

scholarly journals Relationships between Gulf of California Moisture Surges and Tropical Cyclones in the Eastern Pacific Basin

2005 ◽  
Vol 18 (22) ◽  
pp. 4601-4620 ◽  
Author(s):  
R. W. Higgins ◽  
W. Shi
Keyword(s):  
Tropical Cyclones ◽  
Gulf Of California ◽  
Eastern Pacific ◽  
Pacific Basin ◽  
Northwestern Mexico ◽  
Regional Reanalysis ◽  
Relative Differences ◽  
National Hurricane Center ◽  
Tropical Moisture ◽  
Climate Prediction Center

Abstract Relationships between Gulf of California moisture surges and tropical cyclones (TCs) in the eastern Pacific basin are examined. Standard surface observations are used to identify gulf surge events at Yuma, Arizona, for a multiyear (July–August 1979–2001) period. The surges are related to TCs using National Hurricane Center 6-hourly track data for the eastern Pacific basin. Climate Prediction Center (CPC)- observed daily precipitation analyses and the NCEP Regional Reanalysis are used to examine the relative differences in the precipitation, atmospheric circulation, and moisture fields for several categories of surge events, including those that are directly related to TCs, indirectly related to TCs, and not related to TCs. It is shown that the response to the surge in the southwestern United States and northwestern Mexico is strongly discriminated by the presence or absence of TCs. Surges related to TCs tend to be associated with much stronger and deeper low-level southerly flow, deeper plumes of tropical moisture, and wetter conditions over the core monsoon region than surges that are unrelated to TCs. The response to the surge is also strongly influenced by the proximity of the TC to the Gulf of California (GOC) region. Tropical cyclones that track toward the GOC region exert a stronger, more direct influence on Yuma surges than those that track away from the GOC.

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