| Autor: |
Torres-Carrillo, Xochitl Guadalupe, Delgado-Argote, Luis Alberto, Weber, Bodo, Contreras-López, Manuel, Peña-Alonso, Tomás Alejandro, Avilez-Serrano, Porfirio, Gómez-Álvarez, Doris Karina |
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| Zdroj: |
International Geology Review; Mar2023, Vol. 65 Issue 5, p779-805, 27p |
| Abstrakt: |
Cretaceous plutons of the Peninsular Ranges batholith (PRB) intruded two different host rock sequences in the central part of the Baja California peninsula, Mexico. The western sequence is the volcanic-volcaniclastic Alisitos oceanic arc, and the eastern lithologies are mainly metasedimentary pre-Mesozoic units. We analyze the ~116 Ma San Jerónimo (SJe) pluton in the PRB western zone and the Compostela (COM) and San Pedro (SP) plutons (~97 Ma and ~104 Ma, respectively) in the PRB eastern zone. The SJe pluton varies from pyroxene-hornblende gabbro to hornblende-biotite tonalite. Their rocks are subalkaline, calcic/calc-alkaline, and metaluminous, which are akin to island arc granite settings; and yield εNdt values of +5.6 and +6.8, indicating a depleted mantle source without discernible crustal assimilation. The SJe pluton shows subparallel REE patterns (LaN/YbN = 0.5–4.4), with progressive enrichments in REE abundances in the tonalites, suggesting differentiation by fractional crystallization of a single magmatic system. Also, show low Sr/Y values (<20) and La/Yb (<10), suggesting a thin (~20 km) crust beneath the western zone of this Alisitos arc segment. The COM pluton varies from biotite tonalite and biotite-hornblende granodiorite. The SP pluton consists of biotite-muscovite granodiorite and biotite-muscovite granite. These rocks from COM and SP are subalkaline, magnesium, calcic/calc-alkaline, and mainly peraluminous. The eastern zone plutons yield εNdt values from +4.2 to −2.3, indicating mantle-derived melts with the contribution of assimilated crustal material. Their strongly fractionated REE patterns (LaN/YbN = 8–38.3) are characteristic of evolved melts or magmas differentiated within the crust. The high Sr/Y (~90) and La/Yb (~21) further suggest thicker crustal zones (>45 km). Permeation features and parallelism between the metamorphic foliations of the prebatholithic rocks and the magmatic foliation of the plutons indicate a post-deformational emplacement of the mid-Late Cretaceous plutons of the southern PRB. Our data restricts the deformation event before ca. 100–105 Ma. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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