Age,composition, and source of continental arc- and syn-collision granites of the Neoproterozoic Sergipano Belt,Southern Borborema Province,Brazil

The Sergipano belt is the outcome of collision between the Pernambuco-Alagoas Domain (Massif) and the São Francisco Craton during Neoproterozoic assembly of West Gondwana. Although the understanding of the Sergipano belt evolution has improved significantly, the timing of emplacement, geochemistry and tectonic setting of granitic bodies in the belt is poorly known. We recognized two granite age groups: 630–618 Ma granites in the Canindé, Poço Redondo and Macururé domains, and 590–570 Ma granites in the Macururé metasedimentary domain. U–Pb SHRIMP zircon ages for granites of first age group indicated ages of 631 ± 4 Ma for the Sítios Novos granite, 623 ± 7 Ma for the Poço Redondo granite, 619 ± 3.3 Ma for the Lajedinho monzodiorite, and 618 ± 3 Ma for the Queimada Grande granodiorite. These granitoids are dominantly high-K calc-alkaline, magnesian, metaluminous, mafic enclave-rich (Queimada Grande and Lajedinho), or with abundant inherited zircon grains (Poço Redondo and Sitios Novos). Geochemical and isotope data allow us to propose that Sítios Novos and Poço Redondo granites are product of partial melting of Poço Redondo migmatites. Sr-Nd isotopes of the Queimada Grande granodiorite and Lajedinho monzodiorite suggest that their parental magma may have originated by mixing between a juvenile mafic source and a crustal component that could be the Poço Redondo migmatites or the Macururé metasediments. Other 630–618 Ma granites in the belt are the mafic enclave-rich Coronel João Sá granodiorite and the Camará tonalite in the Macururé sedimentary domain. These granites have similar geochemical and isotopic characteristics as the Lajedinho and Queimada Grande granitoids. We infer for the Camará tonalite and Coronel João Sá granodiorite that their parental magmas have had contributions from mafic lower crust and felsic upper crust, most probably from underthrust São Francisco Craton, or Pernambuco-Alagoas Domain. The younger 590–570 Ma granite group is confined to the Macururé metasedimentary domain. Although these granites do not show typical features of S-type granites, their U–Pb age, field relationships, geochemical and Sr-Nd data suggest that their parental magmas have originated from high degree melting of the Macururé micaschists. Field observations support a model in which the Macururé domain, limited by the Belo Monte-Jeremoabo and São Miguel do Aleixo shear zones, behaved as a ductile channel flow for magma migration and emplacement during the Neoproterozoic, very much like the channel flow model proposed for emplacement of leucogranites in the Himalayas.     

Dinosaur ichnofauna of the Upper Jurassic/Lower Cretaceous of the Paraná Basin (Brazil and Uruguay)

Upper Jurassic and Lower Cretaceous sedimentary layers are represented in the Brazilian Paraná Basin by the fluvio–aeolian Guará Formation and the Botucatu Formation palaeoerg, respectively, overlapped by the volcanic Serra Geral Formation. In Uruguay, the corresponding sedimentary units are named Batoví and Rivera Members (both from the Tacuarembó Formation), and the lava flows constitute the Arapey Formation (also in Paraná Basin). Despite the lack of body fossils in the mentioned Brazilian formations, Guará/Batoví dinosaur fauna is composed of theropod, ornithopod and wide–gauge sauropod tracks and isolated footprints, as well as theropod teeth. In turn, the Botucatu/Rivera dinosaur fauna is represented by theropod and ornithopod ichnofossils smaller than those from the underlying units. The analysis of these dinosaur ichnological records and comparisons with other global Mesozoic ichnofauna indicates that there is a size reduction in dinosaur fauna in the more arid Botucatu/Rivera environment, which is dominated by aeolian dunes. The absence of sauropod trackways in the Botucatu Sandstone fits with the increasingly arid conditions because it is difficult for heavy animals to walk on sandy dunes, as well as to obtain the required amount of food resources. This comparison between the Upper Jurassic and Lower Cretaceous dinosaur fauna in south Brazil and Uruguay demonstrates the influence of aridization on the size of animals occupying each habitat.     

Remote sensing and geophysical survey applications for delineating near-surface palaeochannels and shallow aquifer in the United Arab Emirates

This study integrates remote sensing data and geoelectrical dipole–dipole resistivity to delineate near-surface palaeochannels and shallow aquifer in the northern part of Abu Dhabi Emirate, United Arab Emirates. The shuttle imaging radar images and shuttle radar topographic mission DEM were used to delineate near-surface palaeochannels visually based on the contrast between bright and dark tone and automatically using the eight-direction flow model. The delineated palaeochannels were validated by comparing the textural features evident from advanced land observing satellite-phased array type L-band synthetic aperture radar images and determining whether these patterns were different. Field observation and geoelectrical dipole–dipole resistivity method was used to define the depth of palaeochannels and lithology of the shallow aquifer. The remote sensing and geophysical investigations in the UAE, including the study area, indicate the presence of buried palaeochannels with south-west and north-west flow directions from Oman Mountain. The study area can be of economic importance to the local population.     

Visualizing spatiotemporal trajectories of mobile social media users using space–time cube

The implementation of social network applications on mobile platforms has significantly elevated the activity of mobile social networking. Mobile social networking offers a channel for recording an individual’s spatiotemporal behaviors when location-detecting capabilities of devices are enabled. It also facilitates the study of time geography on an individual level, which has previously suffered from a scarcity of georeferenced movement data. In this paper, we report on the use of georeferenced tweets to display and analyze the spatiotemporal patterns of daily user trajectories. For georeferenced tweets having both location information in longitude and latitude values and recorded creation time, we apply a space–time cube approach for visualization. Compared to the traditional methodologies for time geography studies such as the travel diary-based approach, the analytics using social media data present challenges broadly associated with those of Big Data, including the characteristics of high velocity, large volume, and heterogeneity. For this study, a batch processing system has been developed for extracting spatiotemporal information from each tweet and then creating trajectories of each individual mobile Twitter user. Using social media data in time geographic research has the benefits of study area flexibility, continuous observation and non-involvement with contributors. For example, during every 30-minute cycle, we collected tweets created by about 50,000 Twitter users living in a geographic region covering New York City to Washington, DC. Each tweet can indicate the exact location of its creator when the tweet was posted. Thus, the linked tweets show a Twitter users’ movement trajectory in space and time. This study explores using data intensive computing for processing Twitter data to generate spatiotemporal information that can recreate the space–time trajectories of their creators.     

Mediterranean cities under fire. A critical approach to the wildland–urban interface

Wildfires are widely reviewed as key inputs to Mediterranean ecosystems. However, research is often flawed by major biases. (1) The approach adopted by most planners focusing on forest fires dismisses the human dimension of fire as a component of agricultural production systems. (2) The Wildland–Urban Interface (WUI) concept postulates that cities and wildlands/wildfires are, and should remain, worlds apart, a statement whose truth is increasingly questioned by recent disastrous “urban wildfires”. (3) The Mediterranean Basin as a fire-prone area is all the more fantasized, as it is almost never studied as a whole.The present paper takes a critical view of city–wildland/wildfire interrelationships through a large-scale study of the Mediterranean Basin based on MODIS MCD12Q1 (Land Cover Type) and MCD45A1 (Burned Area Product) data collected between 2001 and 2013. The Mediterranean is an ideal place to investigate, as its human-dominated and urbanized landscapes are known to be extremely vulnerable to fire hazards. Data processing reveals that (wild)fires and cities maintain indissoluble ties, as if both elements could not be considered mutually exclusive on a geographical basis. Urban sprawl, reduced rural autonomies, changes in forest covers, old agricultural practices, and military conflicts provide the framework for an extended mitigation process challenging the WUI concept as a space divider.     

Petrology and geochemistry of the Karaj Dam basement sill: Implications for geodynamic evolution of the Alborz magmatic belt

The northeastward subduction of the Neo-Tethyan oceanic lithosphere beneath the Iranian block produced vast volcanic and plutonic rocks that now outcrop in central (Urumieh–Dokhtar magmatic assemblage) and north–northeastern Iran (Alborz Magmatic Belt), with peak magmatism occurring during the Eocene. The Karaj Dam basement sill (KDBS), situated in the Alborz Magmatic Belt, comprises gabbro, monzogabbro, monzodiorite, and monzonite with a shoshonitic affinity. These plutonic rocks are intruded into the Karaj Formation, which comprise pyroclastic rocks dating to the lower–upper Eocene. The geochemical and isotopic signatures of the KDBS rocks indicate that they are cogenetic and evolved through fractional crystallization. They are characterized by an enrichment in LREEs relative to HREEs, with negative Nb–Ta anomalies. Geochemical modeling using Sm/Yb versus La/Yb and La/Sm ratios suggests a low-degree of partial melting of a phlogopite–spinel peridotite source to generate the KDBS rocks. Their low I_Sr = 0.70453–0.70535, ɛNd (37.2 Ma) = 1.54–1.9, and T_DM ages ranging from 0.65 to 0.86 Ga are consistent with the melting of a Cadomian enriched lithospheric mantle source, metasomatized by fluids derived from the subducted slab or sediments during magma generation. These interpretations are consistent with high ratios of ²⁰⁶Pb/²⁰⁴Pb = 18.43–18.67, ²⁰⁷Pb/²⁰⁴Pb = 15.59, and ²⁰⁸Pb/²⁰⁴Pb = 38.42–38.71, indicating the involvement of subducted sediments or continental crust. The sill is considered to have been emplaced in an environment of lithospheric extension due to the slab rollback in the lower Eocene. This extension led to localized upwelling of the asthenosphere, providing the heat required for partial melting of the subduction-contaminated subcontinental lithospheric mantle beneath the Alborz magmatic belt. Then, the shoshonitic melt generates the entire spectrum of KDBS rocks through assimilation and fractional crystallization during the ascent of the magma.     

White mica K–Ar geochronology of Sanbagawa eclogites from Southwest Japan: implications for deformation-controlled K–Ar closure temperature

White mica (phengite and paragonite) K–Ar ages of eclogite-facies Sanbagawa metamorphic rocks (15 eclogitic rocks and eight associated pelitic schists) from four different localities yielded ages of 84–89 Ma (Seba, central Shikoku), 78–80 Ma (Nishi-Iratsu, central Shikoku), 123 and 136 Ma (Gongen, central Shikoku), and 82–88 Ma (Kotsu/Bizan, eastern Shikoku). With the exception of a quartz-rich kyanite-bearing eclogite from Gongen, white mica ages overlap with the previously known range of phengite K–Ar ages of pelitic schists of the Sanbagawa metamorphic belt and can be distinguished from those of the Shimanto metamorphic belt. The similarity of K–Ar ages between the eclogites and surrounding pelitic schists supports a geological setting wherein the eclogites experienced intense ductile deformation with pelitic schists during exhumation. In contrast, phengite extracted from the Gongen eclogite, which is less overprinted by a ductile shear deformation during exhumation, yielded significantly older ages. Given that the Gongen eclogite is enclosed by the Higashi-Akaishi meta-peridotite body, these K–Ar ages are attributed to excess ⁴⁰Ar gained during an interaction between the eclogite and host meta-peridotite with mantle-derived noble gas (very high ⁴⁰Ar/³⁶Ar ratio) at eclogite-facies depth. Fluid exchange between deep-subducted sediments and mantle material might have enhanced the gain of mantle-derived extreme ⁴⁰Ar in the meta-sediment. Although dynamic recrystallization of white mica can reset the Ar isotope system, limited-argon-depletion due to lesser degrees of ductile shear deformation of the Gongen eclogite might have prevented complete release of the trapped excess argon from phengites. This observation supports a model of deformation-controlled K–Ar closure temperature.     

Evolution of continental crust of the Aravalli craton,NW India,during the Neoarchaean–Palaeoproterozoic: evidence from geochemistry of granitoids

Neoarchaean–Palaeoproterozoic granitoids of the Aravalli craton, represented by four plutons with different ages, viz. Gingla (2.6–2.4 Ga), Ahar River (2562 Ma), Untala (2505 Ma), and Berach (2440 Ma) granitoids, are classified into three suites: TTG-like, Sanukitoid, and High-K Granitoid suite, all exhibiting negative Nb and Ti anomalies. The TTG-like suite is characterized by high contents of SiO₂, Na₂O, and LREEs, high (La/Yb)_N, low contents of K₂O, MgO, Cr, and Ni, and low (Dy/Yb)_N, suggesting that this suite formed by partial melting of a subducted basaltic slab without interacting with a mantle wedge. In contrast, the calc-alkaline Sanukitoid suite is marked by a high content of LILEs and mantle-compatible elements, which indicate that this suite formed by partial melting of a slab-fluid metasomatized mantle wedge in a subduction-related arc environment. On the other hand, the High-K Granitoid suite is characterized by high contents of SiO₂ and K₂O, and low contents of Na₂O, MgO, Cr, and Ni with variable Eu anomaly, along with high (La/Sm)_N and (La/Yb)_N, and low (Dy/Yb)_N and Nb/Th. Some high-K granitoids also exhibit A-type characteristics. These features indicate that the High-K Granitoid suite formed by melting of crustal rocks. Early Neoarchaean continental crust formation reflected a slab-melting-dominated magmatic process as evidenced by the TTG-like suite, whereas Palaeoproterozoic petrogenesis was governed by the interaction of slab melt with mantle wedge as demonstrated by the Sanukitoid suite. The High-K Granitoid suite formed during the waning stages of subduction. This study reveals that granitic rocks of the Aravalli craton evolved from slab melting in the Neoarchaean to melting of mantle wedge in the Palaeoproterozoic. Melting of older crust led to the formation of the High-K Granitoid suite.     

Developing markets for water reallocation: Revisiting the experience of Spanish water mercantilización

Economic instruments are being promoted as a desirable alternative to public sector action in the allocation and management of natural resources. A wide body of literature has developed that critically analyzes this phenomenon as part of a wider project of ‘neoliberalization of nature’, trying to uncover the underlying rationale and commonalities of geographically specific phenomena. The case of water is at the vanguard of these processes and is proving to be particularly contentious. In the European Union water policies are increasingly emphasizing the application of economic instruments to improve the allocative equity and economic efficiency in the use of scarce resources. However, there are few analyses of how these instruments are really working on the ground and whether they are meeting their objectives. This paper aims to contribute to this debate by critically analyzing the experience with water markets in Spain, the only country in the European Union where they are operative. It looks at water permit sales during the 2005–2008 drought period using the Tajo–Segura transfer infrastructure. The paper describes how the institutional process of mercantilización of water works in practice in Spain. It shows that the use of markets requires an intense process of institutional development to facilitate and encourage their operation. These institutions tend to favor the interests of clearly identifiable elites, instead of the public interest they supposedly promote.