Sinistral shear during Middle Jurassic emplacement of the Matancilla Plutonic Complex in northern Chile (25.4° S) as evidence of oblique plate convergence during the early Andean orogeny

Mavor, Skyler; Singleton, John S.; Heuser, Gert; Gomila, Rodrigo; Seymour, Nikki M.; Williams, S.; Arancibia, Gloria

doi:10.1016/j.jsames.2022.104047

Cited by 3 publications

(3 citation statements)

References 41 publications

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“…This date overlaps with the weighted mean 206 Pb/ 238 U age of 152.1 ± 2.6 Ma (2-sigma; MSWD = 1.3; n = 12]), and with the inverse isochron (i.e., Tera-Wasserburg) date of 153.5 ± 3.0 Ma (2-sigma; MSWD = 15; n = 12) also obtained in this study. The Concordia age agrees with previously reported U–Pb dates for the earliest crystallization stages of the Matancilla Intrusive Complex (Álvarez et al 2016 ; Mavor et al 2022 and references therein). In situ initial Hf values from the above mentioned 12 individual zircon grains, and calculated using the Concordia age, range from εHf i of + 8.0 (analysis 11a) to an εHf i of + 9.7 (analysis 37a), which suggests a dominantly juvenile source, i.e., produced in the primitive mantle, but with some incorporation of less radiogenic Hf inherited from continental crust through assimilation during emplacement (εHf i = + 10.59 to + 16.56 for Mesozoic rocks of the Canadian Cordillera, Vervoort and Blichert-Toft 1999 ).…”

Section: Resultssupporting

confidence: 90%

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The Montecristo mining district, northern Chile: the relationship between vein-like magnetite-(apatite) and iron oxide-copper–gold deposits

et al. 2023

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The Montecristo district, northern Chile, is one of the few places worldwide where there is a direct relationship between magnetite-(apatite) (MtAp) mineralization and iron oxide-copper–gold (IOCG) mineralization. The MtAp mineralization includes Ti-poor magnetite, fluorapatite, and actinolite and is crosscut and partially replaced by a younger IOCG mineralization that includes a second generation of actinolite and magnetite with quartz, chalcopyrite, pyrite, and molybdenite. The MtAp stage at Montecristo is interpreted as the crystallized iron-rich melts that used the pre-existing structures of the Atacama Fault System as conduits. These rocks later acted as a trap for hydrothermal IOCG mineralization. Geochronology data at Montecristo indicate that the host diorite (U–Pb zircon 153.3 ± 1.8 Ma, 2-sigma), MtAp mineralization (40Ar-39Ar in actinolite, 154 ± 2 Ma and 153 ± 4 Ma, 2-sigma), and the IOCG event (Re-Os on molybdenite, 151.8 ± 0.6 Ma, 2-sigma) are coeval within error and took place in a time span of less than 3.4 Ma. The εHfi and εNdi values of the host diorite are + 8.0 to + 9.8 and + 4.3 to + 5.4, respectively. The whole-rock 87Sr/86Sri values of the IOCG mineralization (0.70425 to 0.70442) are in the lower end of those of the MtAp mineralization (0.70426–0.70629). In contrast, εNdi values for the IOCG mineralization (+ 5.4 and + 5.7) fall between those of the MtAp rocks (+ 6.6 to + 7.2) and the host diorite, which suggests that the IOCG event was related to fluids having a more crustal Nd (εNdi < + 5.7) composition than the MtAp mineralization. This likely reflects the mixing of Nd from the MtAp protolith and a deep magmatic-hydrothermal source, very likely an unexposed intrusion equivalent to the host diorite. Sulfur isotope compositions (δ34S, + 0.3 to + 3.4‰) are consistent with a magmatic source.

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Section: Resultssupporting

confidence: 90%

“…1 a). The Complex includes multiple lithologies, including granodiorite, diorite, quartz diorite, and monzogranite and have been dated between 178 to 154 Ma (Mavor et al 2022 ). Overall, these plutonic rocks are metaluminous and have tholeiitic to calc-alkaline, to high-K affinities (Álvarez et al 2016 ).…”

Section: The Montecristo Districtmentioning

confidence: 99%

The Montecristo mining district, northern Chile: the relationship between vein-like magnetite-(apatite) and iron oxide-copper–gold deposits

et al. 2023

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“…In the study area, volcanosedimentary rocks of the La Negra Formation and the Punta del Cobre Group outcrop. These geological units are found in the center and south of the intermediate depression and to the west of the basin [39]. On the other hand, the Cenozoic era is characterized by sedimentary rocks that represent the ancient relief at the foot of the mountain range.…”

Section: Study Areamentioning

confidence: 99%

Modeling and Evaluation of the Susceptibility to Landslide Events Using Machine Learning Algorithms in the Province of Chañaral, Atacama Region, Chile

Parra,

González,

Chacón

et al. 2023

Sustainability

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Landslides represent one of the main geological hazards, especially in Chile. The main purpose of this study is to evaluate the application of machine learning algorithms (SVM, RF, XGBoost and logistic regression) and compare the results for the modeling of landslide susceptibility in the province of Chañaral, III region, Chile. A total of 86 sites are identified using various sources, in addition to 86 non-landslide sites. This spatial data management and analysis are conducted using QGIS software. The sites are randomly divided, and then a cross-validation process is applied to calculate the accuracy of the models. After that, from 22 conditioning factors, 12 are chosen based on the information gain ratio (IGR). Subsequently, five factors are excluded by the correlation criterion. After this analysis, two indices not previously utilized in the literature, the NDGI (normalized difference glacier index) and EVI (enhanced vegetation index), are employed for the final model. The performance of the models is evaluated through the area under the ROC (receiver operating characteristic) curve (AUC). To study the statistical behavior of the model, the Friedman nonparametric test is performed to compare the performance with the other algorithms and the Nemenyi test for pairwise comparison. Of the algorithms used, RF (AUC = 0.957) and XGBoost (AUC = 0.955) have the highest accuracy values measured in AUC compared to the other models and can be used for the same purpose in other geographic areas with similar characteristics. The findings of this investigation have the potential to assist in land use planning, landslide risk reduction, and informed decision making in the surrounding zones.

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Magmatism and Polyphase Deformation in the Middle Jurassic Arc of Central Chile: Implications for the Tectonic Development of the Early Andean Margin

Singleton,

Arancibia,

Morata

et al. 2024

Tectonics

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The ∼173–164 Ma Papudo‐Quintero plutonic complex near 32.5°S in central Chile records three deformation events that provide insight into the tectonic development of the early Andean margin. The first event (D1) includes: (a) high‐temperature (>600°C), coaxial‐dominated strain along NE‐ to N‐striking subvertical shear zones; (b) widespread emplacement of granitic dikes that dip gently to steeply NE; and (c) development of narrow (<10 cm thick) strike‐slip and oblique‐reverse shear zones. These D1 structures record NW‐SE to WNW‐ESE transpressional shortening with a component of sinistral shear parallel to the N‐S trending magmatic arc. Zircon and apatite U‐Pb dates and cross‐cutting relations constrain most D1 deformation to ∼166–164 Ma. The second event (D2) occurred during postmagmatic cooling in the Late Jurassic and was characterized by development of pervasive E‐W‐striking veins with alteration halos and minor strike‐slip and normal faults that record N‐S extension in a transtensional regime. Structures associated with the last deformation event (D3) include Late Jurassic to Early Cretaceous mafic dikes, veins, and conjugate strike‐slip faults that record NW‐SE to N‐S shortening in a strike‐slip regime. D1 deformation is consistent with studies from other areas that document NW‐SE shortening ± sinistral transpression along the arc throughout the Jurassic, suggesting this deformation was regional in scale and driven by oblique subduction convergence. Deformation associated with oblique convergence was localized within the active magmatic arc, which was an important process in the early Andean orogeny. As the arc migrated eastward, D2 and D3 structures formed in a low‐stress regime in an arc margin or forearc setting.

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Sinistral shear during Middle Jurassic emplacement of the Matancilla Plutonic Complex in northern Chile (25.4° S) as evidence of oblique plate convergence during the early Andean orogeny

Cited by 3 publications

References 41 publications

The Montecristo mining district, northern Chile: the relationship between vein-like magnetite-(apatite) and iron oxide-copper–gold deposits

The Montecristo mining district, northern Chile: the relationship between vein-like magnetite-(apatite) and iron oxide-copper–gold deposits

Modeling and Evaluation of the Susceptibility to Landslide Events Using Machine Learning Algorithms in the Province of Chañaral, Atacama Region, Chile

Magmatism and Polyphase Deformation in the Middle Jurassic Arc of Central Chile: Implications for the Tectonic Development of the Early Andean Margin

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