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Article

Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex

by
Camila Pineda
1,*,
Gloria Arancibia
1,
Valentina Mura
1,
Diego Morata
2,
Santiago Maza
2 and
John Browning
1
1
Departamento de Ingeniería Estructural y Geotécnica & Centro de Excelencia en Geotermia de los Andes (CEGA), Pontificia Universidad Católica, Santiago 7820436, Chile
2
Departamento de Geología & Centro de Excelencia en Geotermia de los Andes (CEGA), Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago 8370450, Chile
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(4), 418; https://doi.org/10.3390/min15040418
Submission received: 5 February 2025 / Revised: 28 March 2025 / Accepted: 14 April 2025 / Published: 17 April 2025
(This article belongs to the Special Issue Magmatic Evolution through Time of Volcanic Zones: Evidence from Isotopic, Geochemical and Geochronological Data of Eruption Products)
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Abstract

:
The Nevados de Chillán Volcanic Complex is one of the most active of the Southern Volcanic Zone. It is formed by NW-SE-aligned eruptive centers divided into two subcomplexes, namely Cerro Blanco (basaltic andesitic) and Las Termas (dacitic), and two satellite cones (to the SW and NE of the main alignment). Our study of the Shangri-La volcano, which is located between the two subcomplexes, in alignment with the satellite cones, and which produced dacitic lavas with basaltic andesitic enclaves, sheds light on the compositional and structural diversity of the volcanic complex. Detailed petrography along with mineral chemistry allows us to suggest partial hybridization between the enclaves and the host lavas and that mixing processes are related to the generation of the Shangri-La volcano and to other volcanic products generated in the complex. This is supported by mixing trends between the enclaves and the most differentiated units from Las Termas. We argue the presence of two main magma storage areas genetically related to crustal structures. A dacitic reservoir (~950 °C) is fed along NW-SE structures, whereas a deeper mafic reservoir (>1100 °C) utilizes predominantly NE-SW structures. We suggest that the intersection between these sets of structures facilitates magma ascent and controls the Nevados de Chillán plumbing system dynamics.

1. Introduction

Many volcanic centers present variations in both composition and eruptive style throughout their evolution (e.g., [1,2,3]). In many cases, these variations have been attributed to the injection of hotter mafic magma into magmatic reservoirs, disrupting the system stability and leading to mixing and convection dynamics that eventually trigger chamber rupture and eruption ([4] and references therein). Furthermore, explosive eruptions have also been attributed to the intrusion of hotter mafic magma into differentiated magmatic reservoirs [5,6,7,8,9]. The process of magma mixing also explains the great compositional diversity found in volcanic centers and disequilibrium textures presented by their phenocrysts (e.g., [10,11,12,13]). The clearest evidence that a reservoir has an open system behavior and an interaction with mafic injections is the presence of mafic enclaves in their volcanic products (e.g., [14,15,16,17]). A detailed textural and mineralogical study of these enclaves and their interaction with the host lava can provide important information on how magma mixing evolves, as well as the intrinsic conditions (temperature, pressure, composition) of the reservoir [18,19,20,21,22]. The combination of detailed textural and chemical analysis on minerals from these systems can provide valuable information on the pre-eruptive processes involved in the generation of magmas, such as crystallization, decompression, recharge, and heating by injections into a magmatic reservoir [23,24,25]. The development and growth of the reservoir occurs through an intermittent injection of magma [26,27,28,29]. The recharge rate of these injections and the source of feeding basaltic magma are closely related to the stress state in which the volcanic complex is located, since it controls, to a large extent, dyke and sill formation and therefore magmatic ascent, arrest, and emplacement capacity [30]. However, the development of a crustal magma reservoir can also be controlled by the existence of major structures, which have been shown to play an important role in facilitating magma accumulation [31,32,33]. The Nevados de Chillán Volcanic Complex (NChVC) is an ideal location to study the relationship between magma-mixing processes and structural control, as the main eruptive centers are aligned in a NW-SE orientation (Figure 1) and the crustal segment hosting the volcano has been suggested to decouple from the maximum horizontal compressive stress associated with subduction processes following megathrust earthquakes [34,35,36]. Although it has been suggested that a principal NW-SE structure controls magma ascent [37,38], the abundance of NE-SW striking dikes and associated eruptive centers [39,40] indicate stress rotations possibly associated with inter-seismic periods [35] or local fault intersection complexities [36]. This work focuses on the Shangri-La volcano, an eruptive center that produces dacitic lavas with an abundance of mafic enclaves. The volcano is located at the intersection between the NW-SE alignment of the NChVC and an apparent lineament of numerous NE-SW-oriented cones [39].

2. Geological Setting

The Nevados de Chillán Volcanic Complex (NChVC) is located in the South Volcanic Zone (SVZ) at the Andes Cordillera (36°52′ S; 71°23′ W; 3212 m.a.s.l.) (Figure 1a). It comprises 15 eruptive centers aligned in a NW-SE direction (Figure 1b). It overlies a basement formed by volcanic and volcanic–sedimentary rocks from the Early–Middle Miocene Cura-Mallín Formation, the Miocene Santa Gertrudis–Bullileo batholith, and the volcanic rocks from the Late Pliocene–Pleistocene Cola de Zorro Formation [39]. The first registered eruptions associated with the NChVC are 650 ka and correspond to emissions of sub-glacial andesitic lavas [39,42,43]. During the Pleistocene, eruptions of andesitic composition continued until the Late Pleistocene, when a caldera-forming event generated extensive ignimbrites [39,43]. After this event, the volcanic system evolved into two subcomplexes, namely Cerro Blanco to the NW, formed by the Santa Gertrudis, Colcura, Gato, Blanco, Calfú, Pichicalfú, and Los Baños volcanoes; and Las Termas to the SE, formed by the Viejo, Democrático, Chillán, Shangri-La, Pata de Perro, Nuevo, Arrau, and San Sebastián volcanoes and the Chudcún crater [39]. Additionally, there are two Holocene satellite cones, the Parador and Las Lagunillas volcanoes, located to the SW and NE of the main alignment, respectively. Since 30 ka, the subcomplexes have evolved contemporarily but independently: the products associated with the Cerro Blanco subcomplex are dominantly basaltic andesitic to andesitic in composition; meanwhile, the Las Termas subcomplex generated more differentiated, mainly dacitic, compositional products [44]. The differences between these two subcomplexes have been attributed to different parental magmas and/or fractionation histories [44] or residence times [45]. Most of the recent eruptions of the NChVC have been a combination of effusive and explosive in nature, and these occurred in the Las Termas subcomplex.
The NChVC formed in an extensional Cenozoic basin which was elongated in a NW-SE direction [46]. Geophysical evidence (seismicity and ground deformation) indicates that magma in the zone is also aligned and inflating along a NW-SE elongation, which coincides approximately with the location of eruptive center alignments [37,38]. It has been suggested that magma emplaces parallel to this alignment following the occurrence of subduction slab decoupling associated with mega-thrust earthquakes (post-seismic periods), producing a transient 90-degree rotation of the extensional axis lasting years or even decades [32,35]. The presence of numerous dikes striking NE-SW suggests that during inter-seismic periods, magma emplacement occurs approximately parallel to the main regional compression, potentially utilizing pre-existing structures along its path [35,36].
There have been attempts to constrain the location of the main magma reservoir(s) responsible for feeding the volcanic complex. Previous geophysical work suggested the presence of a main reservoir between 4 and 5 km in depth, within a 2 km radius from the active crater located in the Las Termas subcomplex [37,38,47]. However, new constraints suggest an elongated chamber at ~6 km depth, connected to a reservoir at 15 km depth [48]. Finally, petrological approaches suggest a magma plumbing system vertically orientated between approximately 2 and 17 km, with pre-eruptive temperatures ranging between approximately 900 to 950 °C for dacites and close to 1000 to 1050 °C for basaltic andesites and andesites, as well as magma water contents of ~2 wt.% of products from Cerro Blanco and ~3 wt.% Las Termas, respectively [49].
This study focuses on the Shangri-La volcano, which is a dome of 250 m diameter located between the Las Termas and Cerro Blanco subcomplexes [39] and in alignment with the satellite cones (Figure 1b). The lavas associated with this monogenetic vent flow westwards through the Shangri-La valley and erupted at 7.7 ± 2.8 ka [43]. Shangri-La produced blocky lava flows with thicknesses of up to 20 m, and they extend for almost 8 km from their source (Figure 1c). The lavas are dominantly of dacitic composition but with basaltic andesitic enclaves [49].

3. Sampling and Analytical Methods

Nine representative samples were collected from the Shangri-La lavas and their enclaves near the terminus part of the flow (Figure 1b,d), and seven thin sections were made and petrographically described. Four thin sections from lava, enclaves, and their contact were characterized petrographically. Phenocrysts, microphenocrysts, that includes mesocrysts (<500 µm length) and microcrysts (<100 µm length) [50], and microlite phases were identified using optical microscope and backscatter electron (BSE) images in a scanning electron microscope (SEM, FEI Quanta 250) in the Centro de Excelencia en Geotermia de los Andes (CEGA) in the Geology Department at the Universidad de Chile and in the CIEN-UC laboratory at the Pontificia Universidad Católica de Chile. Phase and vesicularity estimations were obtained using image analysis in JMicroVision, with the randomized point-counting tool. For estimation of phenocrysts, groundmass, and vesicularity, optical microscope images were used (we count n = 800 for samples representative of the enclaves and n = 800 for samples representative of the host lava), whereas for the estimation of microlites and glass, detailed BSE images from the groundmass were used (n = 500 for samples representative of the enclaves and n = 500 for samples representative of the host lava).
BSE analyses were taken at 15 kV with a beam size of five microns with an acquisition time between 30 and 45 seconds. Compositions of glass, plagioclase, olivine, pyroxene, and oxides were measured on a JEOL JXA 8230 SuperProbe electron microprobe (EMP) at Stanford University (USA). Analyses in glass were conducted using an accelerating voltage of 15 keV, beam current of 2 nA for Na, K, and Si and of 20 nA for Mg, Al, Ca, Fe, and Mn, and a beam size of 5 µm; for plagioclase, the accelerating voltage was 15 keV, the beam current was 20 nA, and the beam size was 3 µm; for olivine and pyroxene, the accelerating voltage used was 15 keV, the beam current was 100 and 20 nA, respectively, and the beam size was 1 µm; finally, for oxides, the beam current used was 20 nA, with an accelerating voltage of 20 keV and a beam size of 1 µm. The complete database is provided in Supplementary Materials Table S1. Additionally, major elements of whole rock composition for two samples (where enclaves and host lavas were separated) were determined at Granada University using X-ray fluorescence spectrometry (data provided in Supplementary Material Table S1).

4. Results

4.1. Whole Rock Composition

Shangri-La host lavas can be classified as dacites (~66 wt.% SiO2) according to the TAS diagram [51] as other products from Las Termas subcomplex (Figure 2), whereas the enclaves have basaltic andesitic to andesitic composition (~56–57 wt.% SiO2) as the products from the Cerro Blanco subcomplex. There are slight differences between the composition of enclaves reported here and those from previous work [49]. The most evident is the higher MgO contents (5.0–7.2 wt.% versus 4.3 wt.%) and lower Na2O contents (1.3–3.6 wt.% versus 3.9 wt.%).

4.2. Petrography

The Shangri-La volcanic products are composed of dark gray dacitic host lavas with basaltic andesitic enclaves, which range in size from 1 mm to ~50 cm in diameter and are usually sub-rounded with irregular margins (Figure 3a,b). Microscopically, enclaves present lava embayment and even the incorporation of portions of the groundmass into the enclave (Figure 3c–e). At the boundary with the host lava, enclaves become more glass-rich, and there is an apparent interaction between them and the dacite (Figure 3d,e).
The Shangri-La host lava is porphyritic (14% phenocrysts and microphenocrysts, vesicle-free), with plagioclase phenocrysts and plagioclase, orthopyroxene, clinopyroxene, olivine, and Fe-Ti oxides microphenocrysts, with accessory apatite and Cr–spinel as inclusions within the olivine. Plagioclase (10%) is commonly part of glomerocrysts, in some cases along with pyroxenes (~2%) and oxides (~1%); pyroxene is usually partially intergrown with plagioclase crystals, and in some cases, thin melt pockets are found between the crystals (Figure 3f). Olivine microphenocrysts (~1%) show the development ofan orthopyroxene reaction rim. The host lava groundmass (86%) has intersertal texture with microlites of plagioclase (30%), pyroxene (7%), Fe-Ti oxides (1%), and glass (62%). Dacitic host lava vesicles (19%) vary in size, ranging from <0.1 mm to ~5 cm, and are irregular, usually sub-rounded.
Enclaves are porphyritic (49% phenocrysts and microphenocrysts, vesicle-free), with plagioclase and olivine phenocrysts and plagioclase, olivine, orthopyroxene, clinopyroxene, and Fe-Ti oxide microphenocrysts with accessory apatite and Cr–spinel as inclusions in olivine. Plagioclase (41%) is found as isolated crystals, clots, or as part of glomerocrysts along with olivine (3%), pyroxene (3%), and Fe-Ti oxides (2%). In the olivine and plagioclase glomerocrysts, plagioclase is usually as microlite crystals (in some cases as microphenocrysts) and intergrowth with olivine phenocrysts. The olivine phenocrysts usually show evidence of resorption in the largest clots or have an orthopyroxene reaction rim in the smaller clots. Plagioclase boundaries have swallowtail textures (Figure 3e,g). The enclaves’ groundmass (51%) has an intersertal texture with microlites of plagioclase (48%), pyroxene (17%), and Fe-Ti oxides (3%) surrounded by brownish glass pools (32%). Some plagioclase crystals have poikilitic texture with chadacrystals of olivine and pyroxene. Enclave vesicles (14%) vary in size, ranging from <0.1 mm to 3 mm, and present variable shapes from rounded and sub-rounded large vesicles to irregular and angular void-filling shapes, and they tend to be smaller. Some clots found in lavas show similar characteristics to the enclaves previously described and could also correspond to enclaves incorporated within the lava (Figure 3g).

4.3. Mineral Chemistry

Both in the host lavas and in the enclaves, plagioclase is the most abundant mineral and can be divided into different types based on their texture and composition (Figure 4a, see Table 1 for summary).
Type 1 plagioclase corresponds to euhedral phenocrysts with oscillatory zoning. The cores have compositions from An40–50 (rarely An70) and rims of An40 composition, occasionally showing weak resorption textures in cores and mantles. These are present as isolated crystals or in clots along with orthopyroxene and occasionally clinopyroxene. This type is only found in host lavas and comprises most of the plagioclase within it (Figure 5a). Type 2 comprises euhedral to subhedral phenocrysts, with fine sieve textures along almost the entire crystal, with cores mostly between An70–80 (in some cases where the sieve is more pervasive, cores present An60 compositions). They show an overgrowth rim of An70–75 composition, and they are identified both in the enclaves (Figure 5b) and the host lavas (Figure 5c); however, when in enclaves, some crystals show a very thin rim of An55 with a BSE grayscale color similar to microlites. Type 3 comprises subhedral to euhedral microphenocrysts of An60–70, with no evidence of disequilibrium textures found in enclaves (Figure 5d) and host lavas (Figure 5e). In the host lavas, they show a thin rim of An40. Type 4 comprises euhedral to subhedral phenocrysts with different grades of resorption in the core and mantle with inverse zonation (An40–60), and rims of An60, which are only identified in the enclaves (Figure 5f). Microlites of the host lavas were not analyzed due to their small size; however, a comparison between BSE grayscale with the analyzed plagioclase indicates qualitatively that they present An40 composition as rims of plagioclase type 1. A couple of the microlites from the enclaves were analyzed (n = 8) and have an average composition of An54; however, the one in contact with olivine is more anorthitic (An70).
Pyroxene microphenocrysts are present in both lavas and enclaves (Table 1). Clinopyroxene in lavas have similar composition than in the enclaves (En40Fs18Wo41 and En43Fs16Wo41 on average, respectively; Figure 4b); in both cases, they usually show a cryptocrystalline orthopyroxene rim (En60Fs35Wo5) which is thinner in the enclaves (Figure 6a,b). In the enclaves, clinopyroxene is predominant and shows a slight decrease in Fe and increase in Mg toward rims in lavas. In some cases, they present an incipient orthopyroxene core. Orthopyroxenes are in host lavas and enclaves; however, they are scarce in enclaves (En68Fs28Wo4) and more abundant in the host lavas where they usually have lower enstatite content (En60Fs35Wo5), similar to the reaction rims present in clinopyroxene. In the enclaves and the dacites, some of these crystals are in apparent equilibrium with clinopyroxene. In the enclaves, they showed resorption textures and an orthopyroxene reaction rim. Microlites in lavas are mainly orthopyroxene (En65–75Fs20–40Wo3–10) and some clinopyroxene, with a similar composition to microphenocrysts. In the enclaves, they are mainly clinopyroxene, with a similar composition to microphenocrysts and some orthopyroxenes are slightly richer in Mg than in the ones in lavas (En60–80).
Olivine is also present in both host lavas and enclaves; however, it is much rarer in the host lava (Table 1). It usually has Fo84–80 cores with Fo75–70 rims (Figure 4c), when in host lavas, olivine is present as isolated crystals with a cryptocrystalline orthopyroxene reaction rim (En67Fs40Wo3), although scarce clots with the presence of olivine of ~Fo55–60 composition and a very thick orthopyroxene reaction rim were found along with orthopyroxene and An40 plagioclase (Figure 6c). The enclaves only display smaller isolate microphenocrysts with a thick orthopyroxene reaction rim (Figure 6d), and larger glomerocrysts have resorption textures and apparently an incipient reaction rim and a thin rim of Fo75–70 compositions (Figure 6e). In lavas, skeletal textures can be identified in rims, and most are apparently part of an enclave, showing resorption textures (Figure 6f). Most olivine present inclusions of Cr–spinel with Cr# (Cr#= molar Cr/(Fe3+ + Al + Cr)) values between 0.37 and 0.45. In host lavas, Fe-Ti oxides are mainly titanomagnetite and, in lower amounts, ilmenite; meanwhile, in the enclaves, only titanomagnetite is identified, presenting skeletal or resorption textures in some cases.

4.4. Intensive Parameters

Twenty-three analyses of in-contact ilmenite–Ti magnetite pairs from the host lava pass the Mg-Mn equilibrium test in [52] and were used to apply the Fe-Ti oxide thermometer and oxybarometer [53]. Pairs yield temperatures from 981 °C to 891 °C (± 8 °C) with an average of 950 °C (standard deviation σ = 23 °C) and fO2 values vary from 0.2 to −0.3 ΔNNO (±0.1 units) with an average of −0.1 ΔNNO (σ = 0.2 units). A summary of the intensive conditions is provided in Table 2 (see details of calculus of intensive conditions in Supplementary Materials Table S2).
We applied the [54] barometer to clinopyroxene, which yields pressures ranging from 0.1 kbar to 2.2 kbar with an average of 1.5 kbar (σ = 0.6 kbar) and an uncertainty of 1.8 kbar for host lavas, as well as pressures from 0.5 kbar to 5.9 kbar with an average of 2.2 kbar (σ = 1.2 kbar) and an uncertainty of 1.7 kbar for the crystals hosted in enclaves. We also applied the [54] thermometer considering a 2 wt.% H2O for the enclaves and a 3 wt.% H2O for host lavas according to the water content reported in [49] for the Cerro Blanco and Las Termas units, respectively, through the [55] plagioclase–hygrometer. Based on these assumptions, the dacitic host lava yields residence temperatures from 1031 °C to 1094 °C with an average of 1051 °C (σ = 20 °C) and an uncertainty of 37 °C, and the enclave temperatures range from 1049 °C to 1131 °C with an average of 1085 °C (σ = 24 °C) and the same uncertainty of 37 °C.
We also applied the two-pyroxene thermobarometer shown in [56] to enclaves, where only three pairs were in equilibrium, reaching temperatures between 972 °C and 991 °C with an average temperature of 982 °C (σ = 10 °C) and an uncertainty of 60 °C, as well as pressures between 1.3 kbar and 4.2 kbar with an average of 3.1 kbar (σ = 1.6 kbar) and an uncertainty of 3.2 kbar.
Orthopyroxene-melt, clinopyroxene-melt, and olivine-melt thermobarometers from [56] were intended to be applied; however, we found that none of the crystal rims were in equilibrium with the glass composition (neither in the host lavas nor in the enclaves).
Table 2. Summary of intensive conditions for Shangri-La lavas. Abbreviations used in the table. ox: oxides; Cpx: clinopyroxene; Px: pyroxene.
Table 2. Summary of intensive conditions for Shangri-La lavas. Abbreviations used in the table. ox: oxides; Cpx: clinopyroxene; Px: pyroxene.
UnitPhasesIntensive ConditionReferenceAverageRangeStandard
Deviation		Uncertainty
Dacite (host lava)Fe-Ti oxTemperature (°C)[53]950891–981238
Oxygen fugacity (Δ NNO)−0.1−0.3–0.20.20.1
Dacite (host lava)CpxPressure (kbar)[54]1.50.1–2.20.61.8
Temperature (°C)10511031–10942037
EnclaveCpxPressure (kbar)[54]2.20.5–5.91.21.7
Temperature (°C)10851049–11312437
EnclaveTwo PxTemperature (°C)[56]982972–9911060
Pressure (kbar)[56]3.11.3–4.21.63.21

5. Discussion

5.1. Textural Evidence of Magma Mixing

Although the different composition of the products generated by the Las Termas and the Cerro Blanco subcomplexes had allowed others to previously suggest that there are two different reservoirs that had evolved independently [44], the Shangri-La basaltic andesitic enclaves and the presence of enclaves in other products from Las Termas [49] indicate possible mixing processes involved in the generation of both subcomplex eruptions. Moreover, previous work [44,49] has suggested possible mixing processes based on co-linear trends between the Cerro Blanco and Las Termas units. The presence of mafic enclaves is usually associated with an injection of a mafic lava into a richer silicic magma [14]. In these cases, thermal differences between the two magmas usually result in quenching textures, especially in enclave margins [14,18,20]. The irregular boundaries and the incorporation of host lava portions in the enclaves from the Shangri-La lavas suggest that this is the case. Microscopically, the boundary layer between the enclaves and host lava shows lower crystallinity in comparison with the enclave inner areas, which suggests a possible dissolution of plagioclase microlite facilitating the incorporation of enclave crystals into the host lavas [19].
In this sense, our results suggest an open system where a dacitic reservoir is being intruded by hotter mafic injections (Figure 7). The crystal mush from the reservoir would be characterized by crystal clots formed by type 1 plagioclase (An40–50) and both pyroxenes in equilibrium, whereas the eruptible magma would only be in equilibrium with orthopyroxene, as evidenced by the cryptocrystalline rim formed around the clinopyroxene (Figure 6a). A detailed petrographic analysis of the host lava indicates that some of the resident phenocrysts could belong to the enclaves and were probably incorporated due to the hybridization process. Olivine phenocrysts are present in a very low percentage in the host lavas (~1%) and show similar compositions (Fo85 cores with Fo75 rims) with those present in the enclaves. The crystallization of olivine with these compositions is more likely to occur in melts of basaltic and basaltic andesitic composition as represented by the enclaves, and not in a dacitic melt like that represented by the host lava. The interaction with a dacitic melt would allow the development of an orthopyroxene reaction rim [57,58]. Moreover, skeletal textures present in some of these crystals and brownish groundmass that surround others suggest that they could belong to the enclaves (Figure 3g,f). It has been shown that host magmas can contain individual crystals or even crystal populations that were disaggregated from the enclaves due to the chemical and temperature disequilibrium between the enclaves and the host magma [22,59,60]. This process could also explain the presence of the more anorthitic plagioclase in the dacitic host lavas, as those described as type 2 and type 3, that present An70 rim compositions, and they can be chemically and texturally related to the plagioclase of the same type found in enclaves.
On the other hand, enclaves show a porphyritic texture with a high abundance of microlites (68%), with some plagioclase microcysts presenting swallowtail disequilibrium textures (Figure 3), indicating a rapid crystal growth due likely to undercooling, probably related to rapid quenching during the interaction with the cooler dacitic magma (e.g., [18,61,62]). The petrographic analysis from enclaves points to a possible hybridization between the mafic enclaves and the dacite. Type 2 and 3 plagioclases from enclaves show relatively high An content (An70), contrasting with type 4, which has inverse zonation with An40 cores, An60 rims, and resorption textures. We interpreted type 4 plagioclase as crystals derived from an andesitic magma, probably initially similar to the inner parts of type 1 plagioclase, which develop resorption textures due to the interaction with the more mafic composition of the enclaves and growth an An60 rim during the mixing process.
Petrography from enclaves shows a more extensive history prior to the injection and allows us to suggest the presence of even deeper reservoirs feeding magma to the shallower system. Sieve textures present in inner sections of type 2 plagioclase indicate disequilibrium that can be associated with an adiabatic decompression [63], suggesting transportation of the crystal batch. This is supported by the fact that in olivine, the thin lower Fo composition rims (Fo75–70) are developed only where they are not in contact with other crystals from the clots. These observations suggest transportation of the high-Fo core clots (Fo84–80) from a deeper and hotter zone (e.g., [64]). On the other hand, the differences among olivine clots in the enclaves, where some present the development of orthopyroxene reaction rims and no development of thin lower forsteritic rims, whilst others show no orthopyroxene rims and a thin Fo75 rim (Figure 6d and Figure 6e, respectively), suggest that those with orthopyroxene reaction rims resided in a reservoir for enough time to grow the pyroxene around them (e.g., [65]), whereas those without this texture could represent posterior magma recharge and could be responsible for eruption triggering as the orthopyroxene rim was not developed. The olivine phenocrysts found in the host lavas show the development of a very thin orthopyroxene rim, suggesting a short time lapse between their incorporation into the dacitic magma and the eruption [58]. We suggest the presence of a partially crystalized mafic sill beneath the dacitic reservoir, associated with an arrested magma from a previous injection. This is supported by the presence of very scarce clots in the lavas that have olivine with lower forsterite content (~Fo55–60) and thicker orthopyroxene reaction rims than those from the enclaves (Figure 6c). These olivines are related to lower anorthite plagioclase (~An40), which suggests that previous injections could happen earlier in the reservoir that mix and equilibrate over time. A succeeding recharge of a hotter magmatic injection that interacted in the first place with this sill could remobilize crystals within the sill and incorporate them into the eruptible magma body, resulting in a variety of crystals with different crystallization histories in the same lava flow [66,67]. This is further supported by the fact that some type 1 plagioclases present partially resorbed cores (An35–50), and a few crystals show a higher An content after the disequilibrium zone. Crystals that are near the recharging area would develop the disequilibrium textures and more anorthitic rims before the mixing continues and new lower anorthitic rims are developed. Recent geodesy studies on the last eruption in the Las Termas subcomplex provide a consistent viewpoint, as they suggest that repeated mafic injections from a deeper reservoir would be interacting at the base of a shallow reservoir and eventually trigger the different eruptive events recorded between 2016 and 2022 [48].
In the enclaves, bubble shapes vary between rounded and irregular angular void-filling spaces between crystals, which could be due to the interaction of these two mafic magmas. Sub-rounded bubbles could suggest that there was not a crystal network before their formation or a coeval generation along with crystallization [68]; however, the presence of the irregular and angular void-filling vesicles suggests that a volatile exsolution could have happened in the presence of crystalline framework [69]. The presence of these two types of bubbles in the same enclaves could be due to the interaction between a new injection of hotter magma into the partially crystallized mafic sill.
The generation of re-equilibration textures in some minerals in both host lavas and enclaves also suggests that a previous mixing process took place within the reservoir before the eruption. This is clear for the plagioclase crystals that were exchanged between the host lava and enclaves; type 3 plagioclases (An60–70) present in the dacite show the development of a thin An40 rim, which is the same as dacite microlite compositions. This exchange occurs as well with type 4 plagioclase present in enclaves, which, as mentioned before, has a An40 core and a An60 rim close to the microlite enclave compositions (An54). This is also supported by the lack of equilibrium between pyroxene and glass and/or whole rock compositions both in enclaves and host lavas (Supplementary Materials Table S2) that suggests a near constant magma mixing affecting the stability of the system (e.g., [70]).

5.2. Modeling Constraints

Considering major and trace element mixing between enclaves and one of the most evolved products of Las Termas (Democrático lava unit), it is possible to generate the Shangri-La host lava composition with ~15%–22% of the enclave composition (Figure 8 and Figure 9). Mixing trends also show, consistently, that it is possible to generate most of the NChVC product variability from different amounts of mixing between the more mafic enclave composition and the more differentiated unit, especially for the case of the most evolved Las Termas eruptions. For these cases, mixing between 10% and 30% of the enclave composition can cover most of the compositional variation. The presence of enclaves in some units of the LT subcomplex suggest an incomplete mixing between the reservoir and the hotter and deeper sourced mafic magma injections. In the case of the more mafic Cerro Blanco compositions, using 80% to 95% of the enclave composition allowed us to reconcile most of the major and trace element variations.
The generation of other NChVC lava flows from mixing is further supported by the presence of similar plagioclase compositions found within them and in the Shangri-La dacite and their mafic enclaves. Plagioclase compositions from different lava flows of Las Termas show a great variability in anorthite content (An30–95); however, most rim compositions have more restricted ranges of An35–50, overlapping with rim compositions found in the dacitic Shangri-La lava (An35–45, Figure 10a,b). This wide compositional range of plagioclase found in Las Termas units is consistent with the incorporation of crystals from the enclaves of the Shangri-La lava, supporting the notion that mixing processes have an important role in the generation of the entire NChVC. The decrease in the number of crystal cores with higher anorthite content could be associated with the grade of hybridization between the reservoir and the mafic injections in each magma batch. For Cerro Blanco units, this is also evident when plagioclase compositions vary between ~An30 to An80 but rim compositions are usually between An40–55. Here, however, a clear marked range of core compositions of An70–80 are preserved, which compositionally overlap with type 2 and 3 plagioclase found in the enclaves (Figure 10c,d). The presence of a higher number of inherited crystals with An70–80 cores in the units from Cerro Blanco suggests a higher proportion of mafic magma needed for the generation of this composition.

5.3. Magmatic Evolution of the NChVC

Shangri-La lavas help us to decipher the processes involved in the generation of the range of compositions that comprise the Nevados de Chillán Volcanic Complex lava products. There is not only a chemical and mineralogical overlap between the host lavas and most of the dacitic products of Las Termas but also a thermal overlap, as the temperatures that we obtained for Fe-Ti oxides of ~950 °C overlap with those previously determined for other Las Termas dacitic products (approximately 900–950 °C), [49].
As discussed before, injections of a hotter mafic magma can be inferred by the presence of the basaltic andesitic enclaves in the Shangri-La lavas. Temperatures recorded by [56] clinopyroxene using the [54] thermometer suggest temperatures of ~1100 °C. This is consistent with previously obtained temperatures for other Cerro Blanco units (~1000–1050 °C, [49]), where generation through mixing involves a major proportion of these injections with a minor thermal contrast and a more efficient mixing. Moreover, there is no substantial evidence for the presence of enclaves in the more mafic end members from Cerro Blanco, which supports the idea of a more efficient mixing.
Finally, the wide range of magma residence depths (between 2 and 17 km) determined for different units in Las Termas and Cerro Blanco [49] could be in part related to mixing and hybridization processes that would allow the coexistence of phenocrysts from different depths in the same units. Although we applied the two-pyroxene [56] thermobarometer, we favor the results obtained with the [54] clinopyroxene barometer, as it has a lower standard deviation and uncertainties. Our results suggest pressures of 1.5 kbar (~6 km depth) for the dacitic reservoir, which has been suggested in [48] as the location for the main reservoir for the last eruption from the NChVC and is consistent with previous geophysical constraints that have determined the location for the active reservoir near the last active center at Las Termas at depths between 4 and 5 km [37,38,47]. Pressures obtained for enclaves generally indicate a deeper source of around 8 km depth (~2 kbar); however, results show a much wider range between ~22 km and ~2 km (5.9 kbar to 0.5 kbar, σ = 1.2 kbar). This pressure range can be explained by the hybrid crystal cargo found in the enclaves, showing that this magmatic system behaves as an open reservoir that is modified by replenishment from deeper and hotter magmas (e.g., [67]). We suggest that the magma is being mixed from a deeper, multiple-reservoir source and fed by dykes, where they can be stored before the final interaction with the dacitic reservoir, which evolves as an open system (Figure 7). This idea is consistent with our textural constraints from enclaves that suggest that magma stalls in more than one reservoir, evidenced especially by olivine clots. Moreover, this can be related with the model proposed in [48], where a deeper reservoir at 15 km is a magma sink that in turn feeds injections into a shallower reservoir ~6 km in depth beneath the Las Termas subcomplex.

5.4. Potential Tectonic Control on the Magma Plumbing System

Several studies have attempted to link the evolution of the magmatic system and eruptions of the NChVC with the presence of crustal faults (see [32,35,36,41]). In these models, magma ascent utilizing NW-SE-oriented structures in the NChVC is of particular interest, as the structures with those orientations seem to be decoupled from the present-day tectonic regime during the inter-seismic phase and only apparently become active during post-seismic transient stress variation [35]. The present-day tectonic setting, instead, facilitates magma ascent along NE-SW structures that align with the sub-horizontal maximum compressive principal stress (σHMax) associated with the subduction process [34]. However, the NW-SE orientation aligns with pre-Andean oblique-slip structures, such as high-angle basement faults, as proposed in [32] for this segment. These pre-existing structures may enhance magma accumulation, as they have been shown to promote the growth and evolution of reservoirs. In this sense, a reservoir can be formed with NW-SE orientation from the accumulation of subsequent mafic injections from deeper magma sources [26,27,28,29]; in this case, it would be evidenced by enclaves present not only in the Shangri-La lavas but also in several units from the NChVC. During inter-seismic phases, the σHMax is oriented NE-SW and acts normal to NW-SE structures, potentially preventing magmatic ascent and promoting magma arrest and sill formation [71]. Under this stress field, mafic dykes striking NE-SW would be favored, and their ascent may be favored along pre-existing structures [31,32,33] if their interception angle was favorable [72]. Pre-existing NE-SW striking structures may locally dilate and favor fluid ascent [36,41,73], suggesting a connection with the monogenetic cones oriented as ENE-WSW and near-inferred lineaments with that orientation such as the Parador, Baños, and Las Lagunillas volcanoes. We suggest that the Shangri-La volcano, which is located roughly in the intersection of the main NW-SE alignment and the ENE-WSW lineaments, would represent the interaction of the main shallow dacitic reservoir with one or more NE-SW striking dykes fed from a deeper mafic reservoir. However, a detailed petrogenetic study of the monogenetic cones is necessary to confirm this hypothesis.
Further supporting this idea, [36] suggested that the interaction between the NE-SW striking Shangri-La and Valle Hermoso faults with the main NW-SE structural alignment facilitates the rotation and emplacement of dykes. This process has also been proposed for the generation of local dilatational areas due the interaction of NE-striking dextral and NW-sinistral striking faults for the generation of NNW-SSE-oriented ore deposits in Río Blanco–Los Bronces and El Teniente [74] and for the distribution of mafic monogenetic volcanos near the Descabezado Grande at the South Volcanic Zone ([75], among others). In this sense, the generation of the Shangri-La volcano could also be related to a similar interaction with a NE-SW-striking fault that cuts between the Cerro Blanco and Las Termas subcomplexes and which promotes dyke injection and interaction with the shallow dacitic reservoir.

6. Conclusions

Understanding the magma plumbing system of the Nevados de Chillán volcanic complex is important, since it is one of the most active volcanoes in the Southern Volcanic Zone of Chile. We have found that enclaves and their host lavas from the Shangri-La lavas, ~7.7 ka, show various forms of evidence indicating partial hybridization, including the following:
(1)
Irregular boundaries between enclaves which exhibit lower crystallinity suggestive of partial melting;
(2)
The presence of olivine and high-An70 plagioclase phenocrysts which are in clear disequilibrium with the host lavas and that can be chemically and texturally associated with the enclaves;
(3)
The presence of plagioclase with disequilibrium textures and lower An40 content that can be related chemically with phenocrysts from the dacite host lava.
These findings suggest that other products from the volcanic complex would also be likely generated by mixing processes. Linear trends for major and trace elements from enclaves to the most differentiated products from the Las Termas subcomplex support a mixing origin for the studied NChVC products between a shallow dacitic reservoir fed by a deeper and more mafic source. This is also supported by the wide range of plagioclase compositions found at the Las Termas and Cerro Blanco subcomplexes, where An70 cores, compositionally related to plagioclase from the Shangri-La mafic enclaves, are found in higher amounts in the less differentiated Cerro Blanco products but also in a minor number of Las Termas units. This is consistent with a variability in the percentage of mixing with the mafic injections, which would be higher at the mafic end (80%–95%) for Cerro Blanco products and lower (10%–30%) for Las Termas products.
Temperatures determined for enclaves indicate that the deeper mafic magmas were at least 1100 °C at the time of interaction with the ~900–950 °C dacitic reservoir, which can be locally heated due to the interaction prior to eruption. Textural evidence from plagioclase and olivine suggest that a mafic sill may have become stalled at the base of the dacitic reservoir and that mixing occurred during a period before the arrival of the latest hotter magma injection, which in turn likely triggered the eruption.
The structural setting where the CVNCh is located suggests that the NW-SE pre-Andean structures from the basement promote magma ascent and accumulation. Although magmatic ascent through these structures would be facilitated during post-seismic periods, during inter-seismic periods, NE-SW structures would control magma ascent and hence may facilitate the injection of dykes into the shallow dacitic reservoir.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/min15040418/s1, Table S1: Whole rock and mineral chemistry; Table S2: Geothermobarometers.

Author Contributions

Conceptualization, C.P., G.A., V.M. and D.M.; methodology, C.P., G.A., V.M., D.M., S.M. and J.B.; investigation, C.P., G.A., V.M., D.M. and J.B.; resources, C.P., G.A., D.M. and S.M.; writing—original draft preparation, C.P., G.A., V.M., D.M. and J.B.; writing—review and editing, C.P., G.A., V.M., D.M. and J.B.; project administration, C.P. and G.A.; funding acquisition, C.P., G.A. and S.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research is funded by ANID Postdoctoral Fondecyt #3240166 and Regular Fondecyt #1220729 grants. This work is also a contribution to the Centro de Excelencia en Geotermia de los Andes.

Data Availability Statement

Data are contained within the article.

Acknowledgments

The authors are grateful to I. Oyarzo (Pontificia Universidad Católica) for her collaboration on field work and to C. Betancourt (Universidad de Chile) for his collaboration on field work and his suggestions to this manuscript. We appreciate the analytical support with EMP analysis by D. Burns (Stanford University). We are grateful for the thoughtful and enriching reviews by the two anonymous reviewers.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a) Location of the Andean volcanic zones in South America: North Volcanic Zone (NVZ), Central Volcanic Zone (CVZ), South Volcanic Zone (SVZ), Austral Volcanic Zone (AVZ). Location of the Nevados de Chillán Volcanic Complex (NChVC) relative to the arc front; (b) NChVC and location of the Shangri-La lavas in yellow, Shangri-La volcano (yellow triangle), Cerro Blanco (CB) subcomplex (red triangles): 1. Santa Gertrudis Vn., 2. Gato Vn., 3. Colcura Vn., 4. Cerro Blanco Vn., 5. Calfú Vn., 6. Pichicalfú Vn., 7. Baños Vn.; Las Termas (LT) subcomplex (purple triangles): 8. Arrau Vn., 9. Nicanor Vn., 10. San Sebastián Vn., 11. Chudcún Vn., 12. Chillán Vn., 13. Viejo Vn., 14. Pata de Perro Vn.; satellite cones (green triangles): 15. Parador Vn., 16. Las Lagunillas Vn.; samples location (light blue stars). Notice that due the closeness of the samples, symbols may overlap; green squares show the range of vision of images (c,d). Geological structures after [41]; (c) Shangri-La volcano and its block-flows lavas; (d) terminus section of the Shangri-La lavas and sample locations (due the closeness of the sampling locations, some symbols overlap).
Figure 1. (a) Location of the Andean volcanic zones in South America: North Volcanic Zone (NVZ), Central Volcanic Zone (CVZ), South Volcanic Zone (SVZ), Austral Volcanic Zone (AVZ). Location of the Nevados de Chillán Volcanic Complex (NChVC) relative to the arc front; (b) NChVC and location of the Shangri-La lavas in yellow, Shangri-La volcano (yellow triangle), Cerro Blanco (CB) subcomplex (red triangles): 1. Santa Gertrudis Vn., 2. Gato Vn., 3. Colcura Vn., 4. Cerro Blanco Vn., 5. Calfú Vn., 6. Pichicalfú Vn., 7. Baños Vn.; Las Termas (LT) subcomplex (purple triangles): 8. Arrau Vn., 9. Nicanor Vn., 10. San Sebastián Vn., 11. Chudcún Vn., 12. Chillán Vn., 13. Viejo Vn., 14. Pata de Perro Vn.; satellite cones (green triangles): 15. Parador Vn., 16. Las Lagunillas Vn.; samples location (light blue stars). Notice that due the closeness of the samples, symbols may overlap; green squares show the range of vision of images (c,d). Geological structures after [41]; (c) Shangri-La volcano and its block-flows lavas; (d) terminus section of the Shangri-La lavas and sample locations (due the closeness of the sampling locations, some symbols overlap).
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Figure 2. Total alkali versus silica (TAS) after [51] for data obtained in this work and previous from the literature [49].
Figure 2. Total alkali versus silica (TAS) after [51] for data obtained in this work and previous from the literature [49].
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Figure 3. Shangri-La host lavas and enclave boundaries. (a) Sub-rounded centimetric mafic enclave in a Shangri-La dacitic lava. (b) Rounded and apparently reabsorbed enclave; (c) evidence of incorporation of host lava into the enclave; (d) apparent dissolution of ground mass from the enclave and incorporation of crystals into the host lavas; (e) incorporation of crystals into the host lavas; (f) glomerocrysts with plagioclase and pyroxene in the host lavas; (g) cumulate at host lava with olivine and groundmass similar to the one from the enclave. Yellow circles show swallowtail texture in plagioclase microcrysts.
Figure 3. Shangri-La host lavas and enclave boundaries. (a) Sub-rounded centimetric mafic enclave in a Shangri-La dacitic lava. (b) Rounded and apparently reabsorbed enclave; (c) evidence of incorporation of host lava into the enclave; (d) apparent dissolution of ground mass from the enclave and incorporation of crystals into the host lavas; (e) incorporation of crystals into the host lavas; (f) glomerocrysts with plagioclase and pyroxene in the host lavas; (g) cumulate at host lava with olivine and groundmass similar to the one from the enclave. Yellow circles show swallowtail texture in plagioclase microcrysts.
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Figure 4. Composition of crystals from Shangri-La lavas: host in enclave in red and host in dacites (host lavas) in blue. (a) Different types of plagioclase composition; (b) pyroxene composition and (c) olivine composition.
Figure 4. Composition of crystals from Shangri-La lavas: host in enclave in red and host in dacites (host lavas) in blue. (a) Different types of plagioclase composition; (b) pyroxene composition and (c) olivine composition.
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Figure 5. Different plagioclase types observed in the Shangri-La lavas. Plagioclases in the purple frames are hosted in the dacitic host lavas, and plagioclases in the red frames are hosted in enclaves. (a) Type 1 plagioclase with resorption in core and mantle; (b) type 2 plagioclase found in enclaves showing sieve in core and mantle; (c) type 2 plagioclase found in the host lava showing sieve in core and mantle; (d) type 3 plagioclase found in enclaves showing no evidence of disequilibrium, slightly zoned; (e) type 3 plagioclase found in host lavas zoned with a thin rim with the same BSE colors than the microlites; (f) type 4 plagioclase showing resorption in core and mantle.
Figure 5. Different plagioclase types observed in the Shangri-La lavas. Plagioclases in the purple frames are hosted in the dacitic host lavas, and plagioclases in the red frames are hosted in enclaves. (a) Type 1 plagioclase with resorption in core and mantle; (b) type 2 plagioclase found in enclaves showing sieve in core and mantle; (c) type 2 plagioclase found in the host lava showing sieve in core and mantle; (d) type 3 plagioclase found in enclaves showing no evidence of disequilibrium, slightly zoned; (e) type 3 plagioclase found in host lavas zoned with a thin rim with the same BSE colors than the microlites; (f) type 4 plagioclase showing resorption in core and mantle.
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Figure 6. Frames in purple indicate crystals hosted in the host lava and frames in red indicate crystals hosted in the enclaves. (a) Clinopyroxene in the host lavas; the zoomed image shows the development of a thin orthopyroxene reaction rim; (b) clinopyroxene in enclaves; (c) clot in the host lava with olivine lower forsterite content and thick orthopyroxene rim; (d) olivine clots in the enclaves, zoomed image shows the development of the orthopyroxene reaction rim; (e) larger size olivine in the enclaves with thin Fo75 rim and no evident orthopyroxene rim; (f) olivine in the host lavas with resorption and parts similar to enclave groundmass.
Figure 6. Frames in purple indicate crystals hosted in the host lava and frames in red indicate crystals hosted in the enclaves. (a) Clinopyroxene in the host lavas; the zoomed image shows the development of a thin orthopyroxene reaction rim; (b) clinopyroxene in enclaves; (c) clot in the host lava with olivine lower forsterite content and thick orthopyroxene rim; (d) olivine clots in the enclaves, zoomed image shows the development of the orthopyroxene reaction rim; (e) larger size olivine in the enclaves with thin Fo75 rim and no evident orthopyroxene rim; (f) olivine in the host lavas with resorption and parts similar to enclave groundmass.
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Figure 7. Conceptual model of the magmatic processes of the Shangri-La volcano. See text for explanation.
Figure 7. Conceptual model of the magmatic processes of the Shangri-La volcano. See text for explanation.
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Figure 8. Major element mixing trends between more mafic enclave whole rock composition (red square) and the Las Termas more differentiated unit (Democrático unit). Purple symbols represent the host lava composition and red symbols the enclave compositions. Data obtained in this work and from the literature [49].
Figure 8. Major element mixing trends between more mafic enclave whole rock composition (red square) and the Las Termas more differentiated unit (Democrático unit). Purple symbols represent the host lava composition and red symbols the enclave compositions. Data obtained in this work and from the literature [49].
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Figure 9. Trace element mixing trends between enclave whole rock and Las Termas differentiated units. Symbols as in Figure 8.
Figure 9. Trace element mixing trends between enclave whole rock and Las Termas differentiated units. Symbols as in Figure 8.
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Figure 10. Composition of plagioclase from the NChVC. (a) Plagioclase compositions from dacitic host Shangri-la lavas; (b) distribution of compositions of plagioclase hosted in lavas from Las Termas subcomplex (from [49]); (c) plagioclase compositions found in basaltic andesitic enclaves entrained in the Shangri-la lavas; (d) plagioclase compositions hosted in lavas from the Cerro Blanco subcomplex (from [49]).
Figure 10. Composition of plagioclase from the NChVC. (a) Plagioclase compositions from dacitic host Shangri-la lavas; (b) distribution of compositions of plagioclase hosted in lavas from Las Termas subcomplex (from [49]); (c) plagioclase compositions found in basaltic andesitic enclaves entrained in the Shangri-la lavas; (d) plagioclase compositions hosted in lavas from the Cerro Blanco subcomplex (from [49]).
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Table 1. Main characteristics of the different plagioclase types and of main mineral phases from the Shangri-La lavas. Abbreviations used in the table: Cpx: clinopyroxene; Opx: orthopyroxene; Ol: olivine.
Table 1. Main characteristics of the different plagioclase types and of main mineral phases from the Shangri-La lavas. Abbreviations used in the table: Cpx: clinopyroxene; Opx: orthopyroxene; Ol: olivine.
TypeTextureCompositionLocation
1Euhedral with occasional resorption in core and mantleCores of An40–50, (rarely An70), oscillatory, rims An40Host lavas
2Euhedral to subhedral with fine sieve in core and mantleCores of An>60, overgrowth rim of An70–77. When in enclaves, show a very thin rim of An55Host lavas/enclaves
3Subhedral to euhedral with no disequilibrium texturesAn60–70 with a very thin rim when in host lavas An40Host lavas/enclaves
4Euhedral to subhedral, with different grades of resorption in core and mantles. Inverse zonationCores of An40 through rims An60Enclaves
CpxSubhedral with a cryptocrystalline orthopyroxene rimEn40–43Fs18–16Wo41Host lavas/enclaves
OpxEuhedral to subhedral. When in enclaves, showed resorption and clinopyroxene reaction rimsEn60Fs35Wo5 (host lavas), En68Fs28Wo4 (enclaves)Host lavas/enclaves
OlEuhedral to subhedral. When in host lavas, are isolated with a cryptocrystalline orthopyroxene rim, skeletal textures in rims, and resorption. When in enclaves, show resorption and occasionally a thick orthopyroxene reaction rimCores of Fo84–80, in some cases a thin rim of Fo75–70. Host lavas/enclaves
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Pineda, C.; Arancibia, G.; Mura, V.; Morata, D.; Maza, S.; Browning, J. Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex. Minerals 2025, 15, 418. https://doi.org/10.3390/min15040418

AMA Style

Pineda C, Arancibia G, Mura V, Morata D, Maza S, Browning J. Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex. Minerals. 2025; 15(4):418. https://doi.org/10.3390/min15040418

Chicago/Turabian Style

Pineda, Camila, Gloria Arancibia, Valentina Mura, Diego Morata, Santiago Maza, and John Browning. 2025. "Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex" Minerals 15, no. 4: 418. https://doi.org/10.3390/min15040418

APA Style

Pineda, C., Arancibia, G., Mura, V., Morata, D., Maza, S., & Browning, J. (2025). Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex. Minerals, 15(4), 418. https://doi.org/10.3390/min15040418

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