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Sixth day: Thursday 17.04.2025.
Stops 21-25. Breakfast 7.30 AM. Mabujina and Escambray complexes along the road Santa Clara-Güinía de Miranda-Trinidad. Time of departure 8 AM.
Below: Geological sketch-map and cross-section (black line) of
central Cuba (based on
Iturralde-Vinent, 1998) with indication of stops.
Below: Geological map of Cuba (1:250000) with indication of stops.
Click here for a high-resolution version.
Click here for
legend.
Below: Stratigraphy of the Cretaceous volcanic arc in Central
Cuba and its relation to the underlying Mabujina Amphibolite
complex (Hu
et al., 2024, slightly modified from
Iturralde-Vinent, 2021).
Stop 21. Amphibolite of the Mabujina Complex (40 min). 22° 2'49.20"N,
79°50'36.01"W.
See
on 1:250K geologic map. See
on geologic sketch map.
See on Google Maps.
See
age relation to stratigraphy of the Cretaceous volcanic arc.
In the Agabama River, amphibolites of the MAC show a variable degree of metamorphism and deformation. Highly deformed amphibolites are well recrystallized and may display proto-mylonitic fabrics defined by amphibole and plagioclase (Grafe et al., 2001). Metatonalitic-metatrondhjemitic rocks alternate with the amphibolites showing a dominant foliation parallel to the main foliation of the amphibolites, thus indicating pre-metamorphic intrusion. Syn-metamorphic felsic layers, dykes, and veins occur parallel and crosscutting the main metamorphic foliation of the amphibolites. They contain small amphibolitic enclaves rich in hornblende interpreted as melanosomic material (i.e., restitic) within trondhjemitic leucosome produced after local partial melting of amphibolite. Locally, these leucocratic bodies are strongly deformed, showing a dynamic recrystallization process. According to their field occurrence related to the amphibolite, the granitoid rocks can be broadly visualized as a dominant group of concordant deformed granitoids and orthogneisses and a less abundant group of concordant to discordant felsic veins.
The oldest ages of granitoids within the MAC date back to ca. 133 Ma suggesting that the basaltic protoliths of the MAC formed since at least Valanginian
time (Rojas-Agramonte et al., 2011).
Below: Photomicrographs of igneous and metamorphic rocks from the Mabujina Amphibolite
Complex. (a) Sample LV50: foliated epidote-amphibolite shows relics of magmatic clinopyroxenes. (b) Sample 7LV9: non-foliated amphibolite with remaining porphyritic subvolcanic texture from basaltic protolith. (c) Sample 7LV9: metamorphic amphiboles replacing igneous phenocrysts of clinopyroxene and amphibole. (d) Sample LV52: foliated amphibolite consisting of amphibole and plagioclase. Note porphyroblastic amphibole with small plagioclase inclusion. (e) Sample 8LV20B: medium-grained undeformed tonalite from the MAC with oscillatory-zoned plagioclase crystals. (f) Sample LV43A: concordant felsic vein from the MAC shows mylonitic texture, ribbons of quartz and plagioclase with pressure shadows. White bar indicates 500 µm. (g) Sample 8CF3: completely recrystallized quartz and deformed plagioclase with flame-shape twining in an orthogneiss
from the MAC. Abbreviations: Amp: amphibole; Bt: biotite; Chl: chlorite; Cpx: clinopyroxene; Ep: epidote; Ms: muscovite; Pl: plagioclase; Qtz: quartz.
(Hu
et al., 2024).
Below: Chondrite-normalized REE (a, c, e) and NMORB-normalized extended trace elements patterns (b, d, f)
the MAB. Geochemical data of calc-alkaline rocks of the Cuban arc refer to the Mataguá, Cabaiguán, and Camujiro Formations
(the latter in the Camaguey region, to the East of Santa Clara
region) are from
Hu
et al. (2024) and
Torró et al.
(2020). Geochemical data of the Guerrero Terrane are from
Mendoza and Suastegui
(2000). Geochemical data of the Los Pasos Formation are from
Hu
et al. (2024).
Stop 22. Amphibolite of the Mabujina
Complex of and granitic rocks of the Manicaragua batholith (40 min). 22° 4'0.77"N,
79°47'39.89"W.
See
on 1:250K geologic map. See
on geologic sketch map.
See on Google Maps.
See
age relation to stratigraphy of the Cretaceous volcanic arc.
In the Agabama River. This outcrop will be visited if times allows. The description of this outcrop is very similar to Stop 21, although the granitoids of the Manicaragua batholith with enclaves of amphibolites can be observed
(photos below). The batholith crosscuts the MAC mainly in the northern part, near the contact with the Cretaceous Volcanic Arc, and establishes an upper limit for the magmatic
formation and metamorphism of the MAC at 89 Ma (Rojas-Agramonte et al., 2011).
Below: Amphibolites intruded by granitoids.
Below: Granitoids with inclusions of amphibolites.
The Escambray Complex (stops 23-25 below) crops out in two domes (Trinidad and Sancti Spiritus) tectonically below the Mabujina Amphibolite
Complex (note green-colored rocks around the domes in the map
below). It is made of four major tectonic units (Millán,
1998) with varied metamorphic facies, increasing up in the
pile from greenschist to eclogite facies (units 1 to 3). The
stratigraphic sequences resemble those of the Guaniguanico
terrane in western Cuba (see stratigraphic sequences below after
Iturralde-Vinent, 2021), but it also includes tectonic
mélanges with blocks of eclogite, serpentinite and
high-pressure, normally calcareous, schists that also occur as
dispersed boudins within some lithodemes (particularly, the
Jurassic Loma la Gloria and earliest Cretaceous Cobrito
lithodemes of unit 3). This has led to the idea that the upper
part of the complex represents a mega-mélange (Gavilanes unit of
Stanek et al. 2006,
2019),
an idea disputed by
Álvarez-Sánchez (2021). For a detailed review of the
stratigraphy and geology of the Escambray complex, see
Álvarez-Sánchez, 2023,
Álvarez-Sánchez y Bernal-Rodríguez, 2023a,
2023b).
The age of metamorphism in the Escambray Complex has been set to
ca. 70 Ma in the eclogitic upper unit 3 and slightly younger in
units 2 (ca. 65 Ma) and 1 (ca. 60 Ma), indicating sequential
subduction of the different units (Schneider et al., 2004, Garcia-Casco
et al., 2008,
Despaigne-Díaz et
al., 2016,
2017,
Stanek et al. 2006,
2019,
and references therein).
Below,
Fig. 13 of
Despaigne-Díaz et al. (2017). P-t path obtained using P-T, geochronological and petrological data for the Escambray complex. Data from the Sancti Spiritus dome from Schneider et al. (2004); Stanek et al. (2006) and Rojas-Agramonte et al. (2012). Results from the Trinidad dome from Despaigne-Díaz et al., 2016. Trajectories in red (Unit Ill) and blue (Unit II) are from the Sancti Spiritus dome and Unit I in green from the Trinidad dome. Data from the Samana complex main tectonic units (Escuder-Viruete et al., 2011a) have been included for comparison (see text for Discussion). D1, D2 and D3 are the different deformation events. Major tectonic events are represented as red lines below the main figure.
Below, Fig. 12. of
Stanek et
al. (2019), including the
Mabujina complex. (a) P-T-(t) diagram with cooling paths from the Gavilanes Unit (blue), the Yayabo Unit (purple), greenschist-facies units (brightgreen, Pitajones Unit; dark-green, La Sierrita nappe of Unit I from Despaigne-Díaz et al., 2016) and the MAC North and East (violet)
summarized from Fig. 3; (b) Depth-time trajectories for the various metamorphic units. (c) Schematic sequence of tectonic juxtaposition of
the EC units and MAC in time.
That the eclogitic metamorphic peak of Unit 3 coincides with the vanishing of the Cretaceous volcanic
arc in West-Central Cuba has led to tectonic models
involving the subduction and collision of the
intra-Proto-Caribbean passive-margin terrane Caribeana (Garcia-Casco
et al., 2008).
Below,
FIG. 1 of Garcia-Casco
et al. (2008). Paleogeographic sketches of the Caribbean region for mid- and latest-Cretaceous times (based on IturraldeVinent, 2006), showing the inferred position of Caribeana (denoted by the Cangre, Escambray, and Samaná terranes)
relative to the Mayan and Bahamian borderlands and the Greater Antilles arc. In B, Caribeana (hatched pattern) is in
the course of subduction. The trace of cross-sections of Figure 8 is shown in B.
Below,
FIG. 8 of Garcia-Casco
et al. (2008). Tectonic sketch cross-sections (see Fig. 1A for location) showing the proposed evolution of the northern
margin of the Caribbean plate, metamorphic terranes, and Mayan/Bahamian borderlands. Model for Yucatan intra-arc
Basin adapted from Pindell et al. (2005).
Stop 23. Carbonates of Boquerones lithodeme
(Upper Jurassic-Lower Cretaceous) of Major Unit 4 (topmost in
the structural pile) of the Escambray Complex. 22°01'13.72"N,
79°51'45.19"W.
See on map. See on sketch map.
See on Google Maps.
See on
stratigraphic chart.
The Boquerones lithodeme characterzed by thin strata of calcareous schists and
marbles, normally graphitic, foliated, and rhythmic character.
It contains some boudins of black microgranular dolomitic
marbles with abundant radiolarians, including probably Messozoic
Nassellaria. It also contains intercalations of
metabasite (former dikes or intrusive bodies representative of
passive margin magmatism). It seems that it overlies the
Herradura lithodeme, made of probably Jurassic low-grade
detrital graphitic metasediments correlated to the Loma La
Gloria lithodeme of the Escambray Complex (stop 24) and the San
Cayetano Fm. in Western Cuba (Stop 6).
Stop 24. Güinia de
Miranda-Trinidad road. El Algarrobo village. 21°58'29.50"N,
79°52'42.77"W. Graphitic schists and muscovite+calcite schists
of the Loma La Gloria lithodeme (Jurassic) of the Escambray
Complex (40 min). This lithodeme is correlated to detrital
strata of the San Cayetano Fm. of Western Cuba.
See on map.
See on sketch map.
See on Google Maps.
See on
stratigraphic chart.
This lithodeme (200-400 m in thickness) is made of
coarse-grained quartzitic and quartz-muscovite metasandstones,
generally with abundant albite with frequent cm- to m-thick
intercalations of generally graphitic metapelitic schits rich in
muscovite and more local layers of foliated marbles. Locally, it
contains boudins (tectonic blocks) of eclogites and
serpentinites up to 10 m in thickness and of Algarrobo schists
(strongly crystalline, commonly calcareous garnet-bearing
schists of probable metamorphic-metasomatic origin). The origin
of the lithodeme is debated (pseudostratigraphic relation vs.
tectonic mélange). The Cobrito
lithodeme lies above (Stop 25).
Below, calcite-muscovite schist.
Below, optical images of the calcite-muscovite-chlorite schist
of this stop 24. It also contains rutile (not shown).
Stop 25. Güinia de Miranda-Trinidad road.
21°54'10.23"N, 79°51'27.00"W.
Muscovite+calcite±graphite schists of the Cobrito lithodeme
(Upper Jurassic-Lower Cretaceous) of the Escambray Complex (40
min).
See on map.
See on sketch map.
See on
Google Maps.
See on
stratigraphic chart.
The schistose sequence contains fine strata of generally
(graphitic) dark and, less frequently, light marbles. They may
also appear as mm-to-cm sized boudins with Mesozoic radiolaria
and other microfossils. Like Loma la Gloria lithodeme, it contains boudins of eclogitic
and serpentinitic rocks (photos below) that may reach several meters in size.
It rests above the Loma la Gloria lithodeme (Stop 24).
Arriving at Hotel Las Cuevas in Trinidad at ca. 5 PM. Dinner at
7.30 PM. 8.30 PM, after dinner concluding meeting of the Thomson
Field Forum.
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