The Moroccan Atlas developed through a multiphase tectonic history including Permian‐Jurassic continental rifting and Cretaceous‐Cenozoic intracontinental shortening. New detrital zircon (DZ) U–Pb ...geochronologic results from the Ourika‐Zat region in the Marrakech High Atlas constrain the sediment provenance of prerift sediment sources and synrift and postrift basin fill. Prerift Precambrian‐Cambrian units contain Neoproterozoic DZ from the Pan‐African orogeny. Ordovician rocks contain diagnostic 0.95‐ to 1.28‐Ga DZ that are absent in the West African Craton, suggesting distal sediment sources. Permian rift basin fill contains Permian zircons that constrain maximum deposition age and diagnostic of northern Meseta domain sediment sources. New mapping and cross‐section construction demonstrate that Permian basin fill accumulated in a half‐graben above a southward dipping normal fault that likely guided subsequent inversion. Triassic rift basin fill thickens southward, above a likely northward dipping normal fault. The change in rift basin geometry was accompanied by catchment reorganization, the introduction of southern rift flank sediment sources, and subbasin integration. The southern catchment expanded to encompass Meso‐Archean rocks of the Reguibat Shield situated >800 km southward. Existing and new provenance results from postrift strata document onset of recycling of Atlas rift basin fill during the mid‐Cretaceous and before the onset of compressional inversion. These results highlight the interaction between deformation and sediment routing in an extensional basin and sediment dispersal patterns across continental margins during multiphase deformation. Stratigraphic, structural, and provenance characteristics reveal that the Atlas rift shares similarities with high‐angle and supradetachment basin models, emphasizing the diverse nature of extensional styles.
Plain Language Summary
Throughout Earth history, the plates on the planet's surface have broken apart and collided together via plate tectonics. During these events, the Earth's crust can be deformed and eroded along linear zones called rifts (when plates break apart) and mountain ranges (when plates collide). Sediment produced during these events can be transported across the Earth's surface and preserved as sedimentary rocks in basins. This study investigates the Marrakech High Atlas Mountains of Morocco, where a rift formed and was followed by construction of a mountain range. The paper uses new geologic mapping, a cross section, and new studies of the preserved sedimentary rocks to investigate the Atlas Mountains spanning a Permian–Triassic rift, and Cretaceous to recent mountain building. The information gained from this study tells geoscientists that the earlier rift acted as a weakness in the Earth's crust. This weakness was used again as a site of compression during later collision. These results help geoscientists understand how continental crust forms and evolves during different phases of compression and extension. It also shows how the drainage patterns across continents can be sensitive to plate tectonic forces, which impacts the sediment and nutrients that eventually flow into the ocean.
Key Points
Permian–Triassic half‐graben extensional basins guided deformation during Cretaceous‐Cenozoic inversion
Sediment provenance evolved from northern to southern rift flank sources during Permian–Triassic rifting, with phases of catchment expansion and subbasin integration identified
Sediment provenance results support early Cretaceous unroofing of High Atlas that predates onset of compressional inversion
Scholars have compared and contrasted commercial and social entrepreneurship along a variety of dimensions, suggesting that entrepreneurial antecedents and outcomes differ within a social context. ...However, little is known about whether entrepreneurial processes differ within social contexts. In this paper, we ask to what extent the antecedents and outcomes that make social entrepreneurship unique influence entrepreneurial processes. Using an inputs—throughputs—outputs framework, we assess the relationship between four antecedents (social mission/motivation, opportunity identification, access to resources/funding, and multiple stakeholders) and three outcomes (social value creation, sustainable solutions, and satisfying multiple stakeholders) to the dimensions of entrepreneurial orientation (innovativeness, proactiveness, risk-taking, competitive aggressiveness, and autonomy) (Lumpkin and Dess, Acad Manag Rev 21(1): 135—172, 1996). Our analysis suggests that many entrepreneurial processes remain essentially the same or are affected only slightly. However, autonomy, competitive aggressiveness, and risk-taking are influenced to some extent by the presence of multiple stakeholders and access to resources/funding. Entrepreneurial processes may also differ when applied to efforts to satisfy multiple stakeholders and achieve sustainable solutions. We subsequently discuss the implications of our analysis for future social entrepreneurship research and practice.
The northern margin of the Organya basin (Southern Pyrenees) has a complex structure in which syn-rift Lower Cretaceous carbonates flank a wide Keuper evaporite province, featuring the leading edges ...of the basement-involved thrust sheets of the Pyrenean antiformal stack. Recent studies show that Keuper diapirs and salt walls grew during the Cretaceous extensional episode, conditioning the development of differentiated depocenters and minibasins. The role of salt tectonics during the Pyrenean orogeny has not been addressed in previous structural studies, but present-day cross-sections indicate a Keuper evaporite-bearing vertical thickness of up to 3000 m in the Senterada-Gerri de la Sal area. We infer that salt migration was a determinant mechanism in triggering a gentle northward tilting of the Organya basin during the Eocene-Oligocene, recorded in the La Pobla de Segur and Gurp syn-tectonic conglomerates in a large north-directed onlap, opposite to the main sedimentary influx direction. Contemporaneously, we interpret that salt migration, promoted by conglomerate differential loading, enabled the sinking and rotation of the unrooted Nogueres thrust units (tetes plongeantes). We use new and published structural data for the Lower Cretaceous margin of the Organya basin, combined with structural and clast provenance data from the Cenozoic alluvial fan conglomerates of La Pobla and Gurp, to understand the Lutetian to late Oligocene evolution of the northern margin of the Central South-Pyrenean Unit. The tectono-sedimentary evolution of this area and the salt evacuation patterns are closely related to the exhumation history of the stacked Paleozoic thrust sheets of the Pyrenean hinterland to the north. In this study, we correlate the movements over a mobile substratum and the paleogeographic changes of conglomeratic basins at the toe of an exhuming orogenic interior.
Extensive areas of the Variscan granitic basement in NE Spain display profiles of red-stained albitized facies characterized by albitization of Ca-plagioclase, chloritization of biotite and ...microclinization of orthoclase, along with the alteration of igneous quartz to secondary CL-dark quartz. These profiles have a geopetal structure beneath the Triassic unconformity, with a very intense and pervasive alteration in the upper part that progressively decreases with depth to 150–200 m where the alteration is restricted to the walls of fractures. The red albitized facies contains secondary maghemite and hematite that indicate oxidizing conditions. Dating of microclinized orthoclase and secondary monazite that have formed in the red-stained albitized facies yielded K–Ar and U–Th–Pb
total
ages of 240 and 250 Ma, respectively, suggesting that the alteration developed during the Permian–Triassic period. The geopetal disposition of the red albitized profile with respect to the Triassic unconformity, its large regional extent, and the fracture-controlled alteration in the lower part of the profile indicate groundwater interaction. The
δ
18
O values of albitized plagioclase (+ 11‰), microclinized orthoclase (+ 13‰), and secondary CL-dark quartz (+ 12‰) suggest that the alteration temperature was about 55 °C. This “low” temperature suggests that the alteration occurred during interaction of the granitic rocks with Na-rich fluids below a surficial weathering mantle on the Permian–Triassic palaeosurface. The latter is possibly related to Triassic evaporitic environments in long-lasting, stable landscapes in which Na-rich solutions infiltrated deep regional groundwaters.
The Eocene clastic systems of the Jaca foreland Basin (southern Pyrenees) allow us to identify changes in sediment composition through time. We provide new data on sediment composition and sources of ...the northern Jaca basin, whose stratigraphic evolution from Middle Lutetian deep-marine to Priabonian alluvial systems record a main reorganization in the active Pyrenean prowedge. Petrological analysis shows that the Banastón and the Lower Jaca turbidite systems (Middle–Upper Lutetian) were fed from an eastern source, which dominated during the sedimentation of the Hecho Group turbidites. In contrast, the upper part of the Jaca turbidite systems (Lutetian–Bartonian transition) records an increase in the number of subvolcanic rock and hybrid-sandstone fragments (intrabasinal and extrabasinal grains) being the first system clearly fed from the north. This change is interpreted as associated with an uplifting of the Eaux-Chaudes/Lakora thrust sheet in the northern Axial Zone. The Middle Bartonian Sabiñánigo sandstone derives from eastern and northeastern source areas. In contrast, the overlying Late Bartonian–Early Priabonian Atarés delta records sediment input from the east. The Santa Orosia alluvial system records a new distinct compositional change, with a very high content of hybrid-sandstone clasts from the Hecho Group, again from a northern provenance. Such cannibalized clasts were sourced from newly emerged areas of the hinterland, associated with the basement-involved Gavarnie thrust activity in the Axial Zone.
Cerro Quema is a high sulfidation epithermal Au-Cu deposit with a measured, indicated and inferred resource of 35.98 Mt. @ 0.77g/t Au containing 893,600oz. Au (including 183,930oz. Au equiv. of Cu ...ore). It is characterized by a large hydrothermal alteration zone which is interpreted to represent the lithocap of a porphyry system. The innermost zone of the lithocap is constituted by vuggy quartz with advanced argillic alteration locally developed on its margin, enclosed by a well-developed zone of argillic alteration, grading to an external halo of propylitic alteration. The mineralization occurs in the form of disseminations and microveinlets of pyrite, chalcopyrite, enargite, tennantite, and trace sphalerite, crosscut by quartz, barite, pyrite, chalcopyrite, sphalerite and galena veins.
Microthermometric analyses of two phase (L+V) secondary fluid inclusions in igneous quartz phenocrysts in vuggy quartz and advanced argillically altered samples indicate low temperature (140–216°C) and low salinity (0.5–4.8wt% NaCl eq.) fluids, with hotter and more saline fluids identified in the east half of the deposit (Cerro Quema area).
Stable isotope analyses (S, O, H) were performed on mineralization and alteration minerals, including pyrite, chalcopyrite, enargite, alunite, barite, kaolinite, dickite and vuggy quartz. The range of δ34S of sulfides is from −4.8 to −12.7‰, whereas δ34S of sulfates range from 14.1 to 17.4‰. The estimated δ34SΣS of the hydrothermal fluid is −0.5‰. Within the advanced argillic altered zone the δ34S values of sulfides and sulfates are interpreted to reflect isotopic equilibrium at temperatures of ~240°C. The δ18O values of vuggy quartz range from 9.0 to 17.5‰, and the δ18O values estimated for the vuggy quartz-forming fluid range from −2.3 to 3.0‰, indicating that it precipitated from mixing of magmatic fluids with surficial fluids. The δ18O of kaolinite ranges from 12.7 to 18.1‰ and δD from −103.3 to −35.2‰, whereas the δ18O of dickite varies between 12.7 and 16.3‰ and δD from −44 to −30. Based on δ18O and δD, two types of kaolinite/dickite can be distinguished, a supergene type and a hypogene type. Combined, the analytical data indicate that the Cerro Quema deposit formed from magmatic-hydrothermal fluids derived from a porphyry copper-like intrusion located at depth likely towards the east of the deposit. The combination of stable isotope geochemistry and fluid inclusion analysis may provide useful exploration vectors for porphyry copper targets in the high sulfidation/lithocap environment.
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•Fluid inclusion data reflect the hydrothermal fluid pathway through the Cerro Quema Au-Cu deposit.•δ34S, δ18O and δD isotope geochemistry, δ34S alunite-pyrite geothermometry and composition of mineralizing fluids (δ34SΣS, XSO42− and XH2S).•Integration of fluid inclusions and stable isotopes as tool-generating exploration vectors in porphyry systems.
Combined sandstone petrography and heavy mineral analysis allow to decipher different sediment routing systems that could not be resolved by one method alone in the South Pyrenean foreland basin. We ...apply this approach to deltaic and alluvial deposits of the southern part of the Jaca basin, and in the time equivalent systems of the nearby Ainsa and Ebro basins, in order to unravel the evolution of source areas and the fluvial drainage from the Eocene to the Miocene. Our study allows the identification of four petrofacies and five heavy-mineral suites, which evidence the interplay of distinct routing systems, controlled by the emergence of tectonic structures. Two distinct axially-fed systems from the east coexisted in the fluvial Campodarbe Formation of the southern Jaca basin that were progressively replaced from east to west by transverse-fed systems sourced from northern source areas. In the late stages of evolution, the Ebro autochthonous basin and the Jaca piggy-back basin received detritus from source areas directly north of the basin from the Axial Zone and from the Basque Pyrenees. Coupling sandstone petrography with heavy mineral provenance analysis allows challenging the existing model of the South Pyrenean sediment dispersal, highlighting the relevance of this approach in source-to-sink studies.
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