Heavy Minerals Distribution and Provenance in Modern Beach and Fluvial Sands of the Betic Cordillera, Southern Spain

: This study uses heavy detrital minerals to determine actualistic fluvial and beach sand provenance across the Betic Cordillera (Spain), along the coast from Almeria to Marbella. The Betic Cordillera, primarily composed of metamorphic rocks to the east, supply an assemblage dominated by almandine and graphite, with a longshore dispersal from Almeria to Malaga. Buergerite and hypersthene indicate the provenance of calcalkaline lavas east of Cabo de Gata. The western part of the Betic Cordillera, which comprises the Ronda Peridotite Complex, supplies a chromite and diopside assemblage, with a dispersal from Marbella to Algeciras. Considering these mineralogical suites, the effects of source rock compositions and weathering are evaluated. The heavy mineral species mirror the mineralogy of the source rocks of local outcrops and wider source terranes. The fluvial heavy mineral suites do not differ significantly from those in the beaches except for some unstable species. Unstable species such as olivine, pyroxene, and amphibole do not show evidence of loss because of elevated topography and semiarid climate, which do not affect heavy minerals. This contribution also evaluates the potential of some heavy detrital species as ideal pathfinders in searching for diamonds.


Introduction
It is well known that the integration of framework composition and heavy minerals of modern sands has revealed an important source of information for provenance determination and has proven to be a useful tool in determining to what extent clastic detritus reflects the signature of parent rocks and the effects of source lithologies and textures, climate, weathering, transport, and depositional environments before diagenetic processes obliterate these features (e.g., [1]).Accordingly, these studies have significantly increased in number [2][3][4][5][6][7][8].This research analyzes and interprets the mineralogy of the heavy minerals of modern sands sampled along a nearly 320 km stretch of the Mediterranean coast of Spain from Almeria to Cadiz (Figure 1a).The exposed lithologies belong to the Betic Cordillera, which has a wide spectrum of source rock types and supplies large amounts of detritus to the coastal and deep-marine environments of the Alboran Sea [9].The Betic Cordillera, located in southwestern Spain, is an Alpine orogenic thrust belt consisting of several tectono-stratigraphic thrust units, including metamorphic (low-to high-grade), mantle-exhumed rocks (peridotite complex), sedimentary rocks (carbonate, siliciclastic, and evaporite), and volcanic rocks (e.g., [9]).A previous study [10] showed the main mineralogy of river, beach and offshore sands collected along this margin between Almeria and Cadiz.The authors identified the composition of the sand grains, recognizing three petrologic provinces characterized by distinct detrital modes on the analyzed onshore and offshore sand.These three compositional provinces are Almeria-Malaga Province, Marbella Province, and Almeria-Malaga Province (Figure 1b).The present paper represents a further extension of the previous work because the integration of light and heavy minerals of modern sands has been revealed as an important source of information for provenance determination (e.g., [6,7,11]).The main goals of this study can be summarized as follows: 1.
To differentiate heavy mineral assemblages supplied from different source rocks and assessing the utility of heavy minerals as provenance indicators; 2.
To quantify the degree to which weathering has potentially reduced heavy minerals' diversity; 3.
To determine the role of heavy mineral species as tracers in diamond exploration.
Geosciences 2024, 14, x FOR PEER REVIEW 2 of 17 (carbonate, siliciclastic, and evaporite), and volcanic rocks (e.g., [9]).A previous study [10] showed the main mineralogy of river, beach and offshore sands collected along this margin between Almeria and Cadiz.The authors identified the composition of the sand grains, recognizing three petrologic provinces characterized by distinct detrital modes on the analyzed onshore and offshore sand.These three compositional provinces are Almeria-Malaga Province, Marbella Province, and Almeria-Malaga Province (Figure 1b).The present paper represents a further extension of the previous work because the integration of light and heavy minerals of modern sands has been revealed as an important source of information for provenance determination (e.g., [6,7,11]).The main goals of this study can be summarized as follows: 1. To differentiate heavy mineral assemblages supplied from different source rocks and assessing the utility of heavy minerals as provenance indicators; 2. To quantify the degree to which weathering has potentially reduced heavy minerals' diversity; 3. To determine the role of heavy mineral species as tracers in diamond exploration.To quantify sediment supply from rivers and beaches of the Betic Cordillera in southwestern Spain and to characterize mineralogical fingerprints of detritus produced by different source rock lithologies, we studied eight very-fine-grained river and beach sand samples.
The results are intended to add to the database on the petrographic features of fluvial and coastal sedimentation, highlighting the useful contribution of heavy detrital mineralogy analysis of the sand fraction as a powerful research tool.The approach would also be suitable for comparison with the sediment provenance in geological and physiographic settings similar to the Mediterranean area.

Geology and Physiography of the Source Area
The Betic Cordillera, located in southwestern Spain, is an Alpine orogenic thrust belt consisting of several tectono-stratigraphic thrust units, including metamorphic (low-to high-grade), exhumed mantle rocks (peridotite complex), volcanic rocks, and sedimentary rocks (evaporite, carbonate, siliciclastic) (e.g., [9]).The same tectonic pile is well exposed surrounding the circum-Mediterranean orogenic belt in the Rif Tell and Calabrian arc [13].The Betic Cordillera belongs to the Alpine chains surrounding the western Mediterranean area from the Gibraltar Arc to the Calabria-Peloritani Arc [14][15][16][17].The orogenic belt forms an arc-shaped arm, formed from the last stage of Alpine Orogeny (from late Mesozoic to Cenozoic time) caused by the convergence between the African and the Iberian and Eurasian plates [13,18].The arc shape is in continuity from north to south of the Gibraltar Strait across the Rif Mountains in Morocco, Tell and Atlas in Algeria, and the Italian Peninsula in the Calabrian arc [13].During the Miocene age, the internal zones of all the circum-Mediterranean orogenic belts were affected by uplift.Consequently, orogenic gravitational collapse was driven from the Plio-Pleistocene to Quaternary period by extensional faults that generated intramountain basins [19][20][21][22][23][24].
The southern boundary of Iberia includes the Betic Cordillera, which is divided into an external and internal domain to the north and south, respectively, and a Flysch Zone in the west [25].The external domain includes the Prebetic and Subbetic Zone (Figure 1a-c).The Flysch Zone emerges in the Gibraltar Promontory, including quartzose turbidite sequences and claystones from the Cretaceous to the lower Miocene [26].The internal domain, known as the Betic Zone or Alboran Domain, consists of layered thrust sheets of metasedimentary and sedimentary rocks with an age ranging from the Paleozoic to the Cenozoic (Figure 1a-c).This domain is divided into two main geological units: the Higher Betic Nappe and the Nevado-Filabride Complex.The latter comprise Paleozoic mica schists with garnet and chloritoid-garnet, quartzite, andalusite, cordierite, sillimanite, and garnet gneiss [27].They also include mica schists, marble, calc-schist, albite-epidote amphibolite, metavolcanic rocks, and serpentinites from the Paleozoic to Triassic periods, along with calcareous breccias and dolostones of a Triassic age [9].The Nevado-Filabride Complex is covered by the Higher Betic Nappe, mainly represented by two thin thrust sheets: the Malaguide complexes and Alpujarride.(e.g., [28]).In some areas, the Nevado-Filabride Complex separates the Alpujarride Complex via Triassic metasedimentary terranes, referred to as the Almagride Complex.The Alpujarride Complex has Paleozoic quartzite, (possibly pre-Silurian) epidote schist, garnet-bearing schist, mica schist, and marble.It also includes Permian to Triassic phyllite, quartzite, and graphite-bearing and garnet-bearing schist with interbedded marble and metabasalt, as well as Triassic gypsum, limestone, and dolostone [27].The Alpujarride Complex features the Ronda Peridotite Complex, the most extensively known exposure of upper-mantle rocks worldwide.This complex includes olivine gabbro, peridotite, and spinel or garnet pyroxenite [29], with minimal alteration due to serpentinization [9,27].The Malaguide Complex comprises non-metamorphosed to very-low-grade metamorphic carbonate rocks, shale, sandstone, conglomerate, gypsum, and chert, with Silurian of an early Miocene age.The tectonic units of the Higher Betic Nappe are unconformably overlayed by clastic, evaporite rocks, and carbonate from the early Miocene to the Quaternary period.Additionally, some outcrops of Miocene (7-15 Ma) calc-alkaline volcanic and volcaniclastic rocks (andesite to rhyolite) crop out in the area of the coast from Carboneras to Cabo de Gata (Figure 1; [9]).
In the paper by Critelli et al. [10], the mineralogy of beach and river sands collected along the Mediterranean coast side of the Betic thrust belt between Cadiz and Almeria was studied.The composition of the sand grains allowed the authors to recognize three different petrologic provinces characterized by three distinct detrital modes (Figure 1).The latter correspond from west to east with the physiographic provinces of the Malaga Mountains, Sierra Nevada, and Sierra de los Filabres, renamed by Critelli et al. [10] as follows: 1.
In the Cabo de Gata-Carboneras province, only one sand sample (381) is volcaniclastic, and Critelli et al. [10] have described it as being without a formal definition of a petrographic province.
The elevation of the Betic Cordillera ranges from sea-level to 3478 m, with the higher altitude corresponding to Mount Mulhacen.The northeast-to-southwest segment of the chain includes a nearly continuous alignment of highlands nearly parallel to the coastline [10].The drainage of the chain is to the northwest and the south, and the drainage network consists of local and ephemeral drainages (Figure 2), generally less than 50 km in length, delivering clastic supply to the coast.These streams produce occasional catastrophic floods, transporting rapid sediment to the coast and distributing drift currents along the shore.An inverse relationship has been found between sediment discharge and the extent of the drainage basins due to the capacity of the rivers to react to sudden floods and the absence of areas in the drainage basins where sediments could be stored (e.g., [30]).Currently, the climate along the coast varies from semiarid to desert [31], becoming more arid eastward, with a mean annual precipitation of less than 200 mm, and more humid westward, with a value of nearly 1000 mm.The mean annual temperature isotherm along the coast averages at 18 • C [31].According to these climatic parameters, the weathering efficiency is mainly controlled by mechanical erosion.[1].Consequently, the sand composition may accurately reflect parent rock compositions of the source region without the depletion of unstable minerals in sediments (e.g., [32]).Littoral drift redistributes sediments on narrow, steep beaches, and storm waves can activate a very active surf zone, inducing powerful littoral drift in both the eastern and western directions (e.g., [33]).Specifically, a prevailing eastward littoral drift predominates between Malaga and Almeria, whereas a westward littoral drift characterizes the coastal stretch from Malaga to Cadiz (Figure 1c) [34].Not all the continental clastic supply remains on the shelf because the narrowness of the northern Alboran continental shelf likely favors a quick transfer to deeper sedimentary environments (e.g., [30]).

Materials and Methods
We studied eight very-fine-grained river and beach sand samples (Figure 2, Supplementary Table S1).
We collected four samples from the active main channel and bars in the inner reaches of river channels and high-tide berms at four beach localities (e.g., [10]).

Materials and Methods
We studied eight very-fine-grained river and beach sand samples (Figure 2, Supplementary Table S1).
We collected four samples from the active main channel and bars in the inner reaches of river channels and high-tide berms at four beach localities (e.g., [10]).
These have been analyzed previously for their light mineralogy [10].
The sand was sieved to obtain 3-4 Φ granulometric fractions.These fractions of the sand samples were employed for heavy mineral separation using gravity settling in bromoform, which shows a density of 2.89 g/cm 3 at 20 • C. Magnetite was removed magnetically using a bar magnet, while the remaining heavy minerals were concentrated by passing the fraction multiple times through a Frantz Isodynamic magnetic separator (University Complutense, Madrid, Spain).This procedure concentrated the heavy minerals into five electromagnetic fractions (0.2; 0.5; 1.0; 1.5 and >1.5 A), facilitating their identification [35].Heavy minerals were mounted on a slide for mineralogical analyses and were analyzed through Raman spectroscopy (University of Calabria, Arcavacata di Rende, Italy).We used this analytical instrumentation because it can be applied to thin sections and grain mounts without requiring any special preparation, unlike other mineralogical analytical tools such as X-ray diffraction [36,37].We analyzed 50 grains for each electromagnetic fraction.Raman spectra were directly obtained by focusing the laser beam on the grain surface.Micro-Raman analysis was carried out using a Thermo Fisher DXR Raman microscope (Waltham, MA, USA), equipped with OMNICxi Raman Imaging software 1.0, with an objective of 50×, a grating of 900 ln/mm (full width at half maximum, FWHM), and an electron-multiplying charge-coupled device (EMCCD).A 532.0 nm line (solid-state laser) was used at an incident power output ranging from 1.8 to 7 mW.The spatial resolution of the laser beam was 3-5 µm.The spectra acquisition time ranged from 5 to 40 s [38].The Raman spectra were acquired at a low wavenumber range from ~100 cm −1 to 1500 cm −1 .
Detrital heavy minerals were identified using a comparison between the obtained Raman peaks and the reference spectra reported in the literature (e.g., ) and mineralogical databases (http://www.rruff.info,accessed on 31 May 2024) [63].
Heavy mineral grains of nine selected samples were contained only in the 0.2 A, 0.5 A, and 1.0 A fractions.(Table 1).The percentage of heavy minerals in each sample was calculated by considering all the grains in all magnetic fractions.

Results
Each sedimentary petrofacies in the Betic Cordillera orogen generates siliciclastic sediment with a specific detrital signature for light (e.g., [10]) and heavy detrital mineralogy.
Garnet is characterized by almandine (Figure 5a), which is often in association with graphite (Figure 7).
The Marbella petrofacies is also composed of olivine as forsterite (Figure 6c) and spinel as chromite (Figure 6d).
All the heavy minerals are primarily characterized by morphological features indicative of mechanical weathering.The Marbella petrofacies is also composed of olivine as forsterite (Figure 6c) and spinel as chromite (Figure 6d).All the heavy minerals are primarily characterized by morphological features indicative of mechanical weathering.

Distribution of Heavy Minerals in the Almeria-Malaga Petrofacies
Heavy minerals are concentrated in different electromagnetic Franz fractions (Table 1).Tourmaline-type buergerite, augite, and tremolite are mainly concentrated in electromagnetic fractions 1.0 A and 0.5 A. Specifically, buergerite also characterizes the 0.2 A electromagnetic fraction where kaersutite and hypersthene are also present.Hypersthene is also concentrated in the 0.5 A electromagnetic fraction.This fraction also includes almandine, hornblende, cummingtonite, diopside, omphacite, chloritoid, and monazite.Epidote, sillimanite, and staurolite characterize the 1.0 A electromagnetic Frantz fraction.
In this petrofacies, only one sand sample, from Las Negras beach, is volcaniclastic (Cabo de Gata-Carboneras province), and it will be described without a formal definition of the petrographic province.Specifically, this sand sample is composed mainly of the orthopyroxene hypersthene (~24%), the clinopyroxene augite, diopside, and omphacite (~23%), amphibole (29%), and tourmaline (~24%) (Figure 8).Amphiboles include hornblende, kaersutite and cummingtonite.The tourmaline buergerite is also found in an amount of 24%, compared to that in Rio Morales, where this mineral shows a lower abundance of 16% (Figure 8).

Distribution of Heavy Minerals in the Almeria-Malaga Petrofacies
Heavy minerals are concentrated in different electromagnetic Franz fractions (Table 1).Tourmaline-type buergerite, augite, and tremolite are mainly concentrated in electromagnetic fractions 1.0 A and 0.5 A. Specifically, buergerite also characterizes the 0.2 A electromagnetic fraction where kaersutite and hypersthene are also present.Hypersthene is also concentrated in the 0.5 A electromagnetic fraction.This fraction also includes almandine, hornblende, cummingtonite, diopside, omphacite, chloritoid, and monazite.Epidote, sillimanite, and staurolite characterize the 1.0 A electromagnetic Frantz fraction.
In this petrofacies, only one sand sample, from Las Negras beach, is volcaniclastic (Cabo de Gata-Carboneras province), and it will be described without a formal definition of the petrographic province.Specifically, this sand sample is composed mainly of the orthopyroxene hypersthene (~24%), the clinopyroxene augite, diopside, and omphacite (~23%), amphibole (29%), and tourmaline (~24%) (Figure 8).Amphiboles include hornblende, kaersutite and cummingtonite.The tourmaline buergerite is also found in an amount of 24%, compared to that in Rio Morales, where this mineral shows a lower abundance of 16% (Figure 8).Different to samples from Las Negras beach, in the other beach samples (Punta de la Mona and Lagos), amphibole is represented by tremolite in amounts of 14% and 29% (Table 1; Figure 8), respectively.These minerals are not present in the Rio Morales and Rio Adra samples (Figure 8).In all sand samples, the amount of garnet, composed of almandine species, ranges from 29% to 80% except in Las Negras beach (Figure 8).In both Punta de la Mona and Lagos beach, this mineral is often in association with graphite.This latter is also present as an inclusion in the garnet of Rio Adra.An average value of about 13% of epidote is detected in Rio Morales and Rio Adra (Figure 8).Metasedimentary heavy minerals (~27%) are observed in Rio Morales with the occurrence of chloritoid and in Punta de la Mona beach and with the presence of staurolite and sillimanite (Figure 8).Different to samples from Las Negras beach, in the other beach samples (Punta de la Mona and Lagos), amphibole is represented by tremolite in amounts of 14% and 29% (Table 1; Figure 8), respectively.These minerals are not present in the Rio Morales and Rio Adra samples (Figure 8).In all sand samples, the amount of garnet, composed of almandine species, ranges from 29% to 80% except in Las Negras beach (Figure 8).In both Punta de la Mona and Lagos beach, this mineral is often in association with graphite.This latter is also present as an inclusion in the garnet of Rio Adra.An average value of about 13% of epidote is detected in Rio Morales and Rio Adra (Figure 8).Metasedimentary heavy minerals (~27%) are observed in Rio Morales with the occurrence of chloritoid and in Punta de la Mona beach and with the presence of staurolite and sillimanite (Figure 8).Staurolite in Lagos beach is also found (Table 1).An amount of 14% of monazite is found in Punta de la Mona beach (Figure 8).Carbonates such as ankerite and dolomite are identified in Rio Morales and Rio Adra.
The surface texture of the heavy minerals suites is fresh and angular and does not show etching processes due to dissolution (Figure 3

Distribution of Heavy Minerals in the Marbella Petrofacies
The results of different electromagnetic fractions of Marbella petrofacies are shown in Table 1.These electromagnetic fractions exhibit the concentrations of forsterite, hypersthene, diopside, and actinolite in the 1.0 A and 0.5 A fractions.Moreover, the 0.5 A electromagnetic fraction includes almandine and cummingtonite with respect to the 1.0 A fraction, in which augite and chromite are concentrated.Chromite in the 0.2 A electromagnetic fraction is also observed.
Forsterite occurred in all sand samples, reaching an amount of up to 38% in Rio Guadalmina and decreasing in amount to 18% at Punta del Castor beach (Figure 8).Punta del Castor beach sand hypersthene show a higher value, of about 18%, than the other sand samples.
The river (Rio Guadalmansa) to beach environment transition (Punta del Castor) shows a slight decrease in abundance, ranging from 31% to 27% and 23% to 18%, for diopside, augite, and garnet.Amphiboles is present in higher amounts in Punta del Castor beach (19%) and shows a lower value in the Rio Gualdamina (8%) (Figure 8).Chromite was found in Rio Guadalmina and Rio Guadalmansa (Figure 8).

Betic Cordillera Source Rock Types and Heavy Minerals
The efficiencies of the concentrating processes are not the same for each mineral (e.g., [10,64]), and according to their mobility, the occurring heavy mineral assemblages indicate that these were delivered to the beach environment by rivers as bedload (e.g., [65]).In terms of both water discharge and sediment transport, Andalusian river systems are quite efficient despite the small size of their catchments (e.g., [30]).
In this study, many heavy mineral species were recorded: almandine, hypersthene, augite, diopside, omphacite, hornblende, kaersutite, tremolite, cummingtonite, actinolite, epidote, buergerite, staurolite, chloritoid, sillimanite, forsterite, and chromite.This great variety is interpreted because of the weathering-limited erosion regime within the Betic Cordillera, which has not affected the diversity of the heavy mineral assemblages taken into the bedload rivers and transported to the coast.Clastic sedimentation is characterized by unstable minerals such as olivine and pyroxenes in the sand.The high heavy mineral diversity of this study area demonstrated that they have value as sensitive indicators of both a local and broader scale of provenance.For example, the Rio Morales and Las Negras beach heavy mineral assemblages reflect a restricted outcrop of volcanic rocks at the Cabo de Gata promontory.The main heavy species are buergerite, augite, and hypersthene.Specifically, buergerite was first found in hydrothermally altered tuffs and clayey rhyolites near Mexquitic, San Luis Potosi, Mexico [66], in aplite-pegmatite veins of the Plana Cretaceous Pluton in Bulgaria [67] and as a detrital mineral in Paleozoic felsic metasedimentary source rocks [68].The mineral suites also reflect variations in the broader scale of provenance from Almeria to Malaga.
The main heavy mineral association of the Almeria-Malaga province is dominated by almandine associated with graphite, which is often present as an inclusion in almandine.Specifically, graphite can be considered a provenance-diagnostic detrital species (e.g., [69]) ascribed to sediment supplies mainly from small outcrops of the graphite-bearing schists of the Alpujarride Complex (Figures 1c and 7).The assemblage of sillimanite, staurolite, almandine, chloritoid, monazite, and epidote are ascribed to provenance from the Nevado-Filabride Complex metamorphic rocks (Figures 1c and 8).In contrast, the presence of dolomite suggests that this detrital species is supplied by metasedimentary lithotypes of the Nevado-Filabride Complex and the Alpujarride Complexes (Figures 1 and 8).In Marbella Province [10], the Ronda Peridotite Complex, including peridotites, gabbros, and serpentinites [19], is dominated by olivine as forsterite, chromite, and diopside (Table 1, Figures 1c and 8).Even though the ultramafic rocks of the Ronda Peridotite Complex represent a restricted outcrop area, the abundance of ultramaficlastic heavy species is much higher than that of almandine supplied by the garnet-bearing schists of the Alpujarride Complex (Figures 1 and 8), which has a much wider areal extent in the hinterland.The overrepresentation of the ultramaficlastic detritus can be related to a Sand Generation Index [22] for the Ronda Peridotite Complex that is higher than that of the Nevado-Filabride metamorphites.
Therefore, we can confirm that the mineralogy of the river and beach sands analyzed reflects the provenance of source rocks belonging to the catchment.This correlation between mineralogical data and local geological characteristics enhances our understanding of the study area's sedimentary dynamics and erosion sources (Figure 9a-d).
provenance from the Nevado-Filabride Complex metamorphic rocks (Figures 1c and 8).In contrast, the presence of dolomite suggests that this detrital species is supplied by metasedimentary lithotypes of the Nevado-Filabride Complex and the Alpujarride Complexes(Figures 1 and 8).In Marbella Province [10], the Ronda Peridotite Complex, including peridotites, gabbros, and serpentinites [19], is dominated by olivine as forsterite, chromite, and diopside (Table 1, Figures 1c and 8).Even though the ultramafic rocks of the Ronda Peridotite Complex represent a restricted outcrop area, the abundance of ultramaficlastic heavy species is much higher than that of almandine supplied by the garnet-bearing schists of the Alpujarride Complex (Figures 1 and 8), which has a much wider areal extent in the hinterland.The overrepresentation of the ultramaficlastic detritus can be related to a Sand Generation Index [22] for the Ronda Peridotite Complex that is higher than that of the Nevado-Filabride metamorphites.
Therefore, we can confirm that the mineralogy of the river and beach sands analyzed reflects the provenance of source rocks belonging to the catchment.This correlation between mineralogical data and local geological characteristics enhances our understanding of the study area's sedimentary dynamics and erosion sources (Figure 9ad).

Provenance and Weathering of Heavy Minerals
In the provenance studies is formulated an "order of persistence" of the heavy detrital minerals widely used as a measure of mineral stability in sediments (e.g., [71]).Unstable species include andalusite + pyroxenes + amphiboles (APA sensu [11]), epidote + zoisite + kyanite + sillimanite + titanite + brookite (EKS sensu [11]) are considered moderately stable, garnet + apatite + staurolite (GAS sensu [11]) is regarded as stable, and zircon + tourmaline + rutile are considered ultrastable species (e.g., ZTR sensu [72]).Therefore, different heavy minerals display different responses to weathering [5].This study suggests that the effects of chemical and biochemical weathering on the heavy minerals assemblages have been negligible and that mechanical weathering has also been only a modest cause of compositional modification during transport [73].

The Role of Tracer Heavy Minerals in Diamond Exploration
The disaggregation of mantle rocks yields large quantities of mantle minerals, commonly referred to as kimberlitic indicator minerals, and, from an exploration point of view, the most important indicator minerals are garnet, chromite, Cr-diopside and olivine (e.g., [74]).In general, these "kimberlitic indicator minerals" are obviously not unique to kimberlites but also include exhumed mantle peridotites like the Ronda massif.Therefore, kimberlitic indicator minerals can be extracted from medium-to-fine sand in sample surface materials such as soil, stream, and till sediments (e.g., [74][75][76]).Some heavy detrital species, described by Nowicki et al. [74], have been found in the ultramaficlastic Marbella petrofacies (e.g., [10]), confirming that they are supplied from the Ronda Peridotite Complex, which includes peridotite, olivine gabbro, and spinel or garnet pyroxenite as source rocks (e.g., [9,27,29]).Heavy mineral varieties of Betic sand, associated with mantle rocks of the Ronda Peridotite Complex, include garnet, ilmenite, and chromite.These species, considered stable (e.g., [71]), are particularly useful due to their greater ability to survive weathering in the surface environment [5]; thus, in addition to rare diamond, the disaggregation of mantle rocks yields quantities of other mantle minerals, commonly referred to as kimberlitic indicators.

Conclusions
The provenance of the heavy minerals assemblages of the river and beach, from Carboneras to Marbella, located in the Betic Cordillera orogenic terranes, is linked to metamorphic (mainly gneisses and schists), ultramafic (peridotite, olivine gabbro, and spinel or garnet pyroxenite) and calcalkaline volcanic rocks, outcropping in the drainage basins of the Andalusian margin.The eastern Betic Cordillera supplies two assemblages: one widespread and dominated by almandine and graphite, derived from garnet-sillimanite gneiss, forming the larger part of the outcrops, and the other by buergerite and hypersthene, identifying a small outcrop of andesite to rhyolite effusive rocks.The western Betic Cordillera supplies an assemblage dominated by forsterite, chromite, and diopside, closely matching the ultramafic bedrock lithology of the Ronda Peridotite Complex.
The results indicate that the effect of weathering did not influence the heavy mineral suites; even olivine, pyroxene and amphibole, susceptible to chemical loss, are well preserved in the sand, with no sign of corrosion or dissolution.Moreover, some mantle rock-derived heavy minerals, such as garnet, chromite, diopside and olivine, are known as kimberlitic indicator minerals.

Figure 1 .
Figure 1.(a) Location map of the Iberian Peninsula and northwestern part of Africa; (b) geological map of the Iberian and northwestern sector of Africa modified after [12]; (c) tectono-stratigraphic map of southwestern Spain (Betic Cordillera) and northwestern sector of Morocco.The legend of the geological map of panel (a) is shown in Supplementary Figure S1 [12].

Geosciences 2024 , 17 Figure 2 .
Figure 2. Location map of the sample sites and name of the localities.Triangle: river samples; circle: beach samples.

Figure 2 .
Figure 2. Location map of the sample sites and name of the localities.Triangle: river samples; circle: beach samples.

Figure 7 .
Figure 7. Raman spectrum of graphite in Punta de la Mona beach, in the Almeria-Malaga petrofacies.

Figure 7 .
Figure 7. Raman spectrum of graphite in Punta de la Mona beach, in the Almeria-Malaga petrofacies.

Figure 9 .
Figure 9. (a) Geological map of the southwestern part of the Betic Cordillera (from [64]), with the location sites (black rectangles and square); (b) 2D map view of the lithology of Marbella study area with the location sites; (c) 2D map view of the lithology of Malaga study area with the location sites; (d) 2D map view of the lithology of Almeria site with the location sites.The legend of this map is shown in the Supplementary Figure S2 [70].

Figure 9 .
Figure 9. (a) Geological map of the southwestern part of the Betic Cordillera (from [64]), with the location sites (black rectangles and square); (b) 2D map view of the lithology of Marbella study area with the location sites; (c) 2D map view of the lithology of Malaga study area with the location sites; (d) 2D map view of the lithology of Almeria site with the location sites.The legend of this map is shown in the Supplementary Figure S2 [70].