Hydrogeochemistry and quality of groundwater of coastal unconfined aquifer in Amol–Ghaemshahr plain,Mazandaran Province,Northern Iran

Groundwater of the unconfined aquifer (1,100 sq. km) of a two-tier coastal aquifer located in the Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran, is classified into fresh and brackish water types. Fresh groundwater (FGW) samples (n = 36) are characterized by Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃ ^? > Cl^? > SO₄ ^2? > NO₃ ^?. Spearman’s rank correlation coefficient matrices, factor analysis data, values of the C-ratio (av. = 0.89) and CAI and values of the molar ratios of Ca²⁺/HCO₃ ^?, Ca²⁺/SO₄ ^2?, Mg²⁺/HCO₃ ^? and Mg²⁺/SO₄ ^2? indicate that the ionic load in the FGW is derived essentially from carbonic acid-aided weathering of carbonates and aluminosilicates, saline/sea water trapped in the aquifer sediments (now admixed with the groundwater) and ion exchange reactions. Values of the CAI and Na⁺/Cl^? molar ratio suggest that the part of the Ca²⁺ (±Mg²⁺) content in 23 FGW samples is derived from clay minerals of the aquifer matrix, and part of the Na⁺ content in 20, 12, and 3 FGW samples is derived, respectively, from alkali feldspar weathering, clay minerals of the aquifer matrix and rain water and/or halite. Brackish groundwater (BGW) samples (n = 4) contain Cl^? as the dominant anion and their average total ionic concentration (38.65 meq/L) is 1.79 times higher than that of the FGW samples (21.50 meq/L). BGW pockets were generated by non-conservative mixing of FGW with the upconed saline water from the underlying saline groundwater zone of the semi-confined aquifer along bore wells involved in excessive extraction of groundwater from the unconfined aquifer. Groundwater belongs essentially to “high salinity, low sodium” irrigation water class.     

Different response of vegetation to permafrost change in semi-arid and semi-humid regions in Qinghai–Tibetan Plateau

The effects of the depth of the active layer of permafrost on aboveground vegetation in semi-arid and semi-humid regions of the Qinghai–Tibetan Plateau were studied. The depth of active permafrost was measured and aboveground vegetation recorded. Differences in correspondence between permafrost depth and aboveground vegetation in semi-arid and semi-humid regions were analyzed. Vegetation cover and biomass were well correlated with permafrost depth in both semi-arid and semi-humid regions, but the correlation coefficient in the semi-arid region was larger than in the semi-humid region. With the increase in permafrost depth, vegetation cover and biomass decreased in both regions. Species richness and diversity decreased with increasing depth of permafrost in the semi-arid region. In the semi-humid region, these at first increased and then decreased as permafrost depth increased. It seems likely that vegetation on the Qinghai–Tibetan Plateau will degenerate to different degrees due to permafrost depth increasing as a result of climatic warming. The influence would be especially remarkable in the semi-arid region.     

The use of the weights-of-evidence modeling technique to predictive porphyry Cu potential mapping in Ahar–Arasbaran zone,Iran

The weights-of-evidence is a data-driven method that provides a simple approach to integration of diverse geo-data set information. In this study, we will use weights-of-evidence to build a model for predicting tracts in the Ahar–Arasbaran zone of Urumieh-Dokhtar orogenic belt (northwestern Iran) that are favorable for porphyry copper deposits. Weights of evidence are a data-driven method requiring known deposits and occurrences that are used as training points in the evaluated area. This zone hosts two major porphyry Cu deposits (The Sarcheshmeh deposit contains 450 million tonnes of sulfide ore with an average grade of 1.13 % Cu and 0.03 % Mo and Sungun deposit, which has 500 million tonnes of sulfide reserves grading 0.76 % Cu and 0.01 % Mo), and a number of subeconomic porphyry copper deposits are all associated with Mid- to Late Miocene diorite/granodiorite to quartz-monzonite stocks. Five evidential layers including geology, alteration, geochemistry, geophysics, and faulting are chosen for potential mapping. Weight factors were determined based on the applied method to generate last mineral prospectivity map. The studied area reduces to less than 11.78 %, while large zones are excluded for further studies. This result represents a significant area reduction and may help to better focus on mineral exploration targeting porphyry copper deposits in the Ahar–Arasbaran zone.     

Evaluation of changes in ecological security in China’s Qinghai Lake Basin from 2000 to 2013 and the relationship to land use and climate change

Ecological security evaluation is an important way to identify the need for improvement in a watershed and to assess the degree of regional sustainable development. Using a driver–pressure–state–exposure–response model, a comprehensive system of ecological security indicators was developed, and it was demonstrated in a case study of the main ecological problems facing the Qinghai Lake Basin. Indicators of the status of the natural ecological environment, socioeconomic pressure, and the degree of environmental damage were chosen to develop the model, and comprehensively evaluated the basin’s ecological security in 2000, 2004, 2009, and 2013 to reveal changes in the ecological security in response to changing climate and land use. The overall ecological security of the basin improved from 2000 to 2013, with considerable restoration and reconstruction of the ecosystem. From 2000 to 2004, environmental deterioration increased slightly as a result of pollution caused by human activities, excess land reclamation for agriculture, land desertification, and grassland degeneration. However, the obvious effect of ecological protection policies, such as conversion of farmland into grassland and stall feeding of livestock instead of grazing, led to improvement of the ecological environment from 2004 to 2013. Ecological security in the basin increased with increasing precipitation during the study period.     

Constraining the timing of porphyry mineralization in northwest Iran in relation to Lesser Caucasus and Central Iran; Re–Os age data for Sungun porphyry Cu–Mo deposit

The Neo-Tethyan subduction in Iran is characterized by the Urumieh–Dokhtar magmatic arc (UDMA), formed by northeast-ward subduction of the oceanic crust beneath the central Iran. This belt coincides with the porphyry copper metallogenic belt that comprises several metallogenic zones, including Ahar–Jolfa in northwest Iran. The Ahar–Jolfa metallogenic zone encompasses two main batholiths of Qaradagh and Sheyvardagh and numerous intrusive bodies of Cenozoic, which have produced many base and precious metal deposits and prospects. The former is considered as continuation of the Meghri–Ordubad pluton in South Armenian Block (SAB), which also hosts porphyry copper deposits (PCDs). The Sungun PCD is the largest occurrence in northwest Iran. Rhenium-Osmium ages of Sungun molybdenites are early Miocene and range between 22.9 ± 0.2 and 21.7 ± 0.2 Ma. Comparison of the ages obtained here with published ages for mineralization across the region suggests the following sequence. The earliest porphyry Cu–Mo mineralization event in northwest Iran is represented by Saheb Divan PCD of late Eocene age, which is followed by the second epoch of middle Oligocene, including the Cu–Mo–Au mineralization at Qarachilar and the Haftcheshmeh PCD. Mineralization in Sungun, Masjed Daghi, Kighal and Niaz deposits corresponds to the third mineralization event in northwest Iran. The first epoch in northwest Iran postdates all Eocene mineralizations in SAB, while the second epoch is coeval with Paragachay and the first-stage of Kadjaran PCDs. Its third epoch is younger than all mineralizations in SAB, except the second stage in Kadjaran PCD. Finally, the Cu mineralization epochs in northwest Iran are older than nearly all PCDs and prospects in Central Iran (except the Bondar Hanza PCD), altogether revealing an old to young trend along the UDMA and the porphyry Cu belt towards southeast, resulted from diachronous, later closure of the Neo-Tethyan oceanic basin in central and SE Iran.     

Vulnerability and resistance to neoliberal environmental changes: An assessment of agriculture and forestry in the Biobio region of Chile (1974–2014)

This article examines the dynamics of double exposure, vulnerability, and resistance to neoliberal globalization and environmental change in the Chilean agricultural region of Biobio. By using climatic models and secondary Agricultural Census data from 1997 and 2007, we assess how Chilean neoliberal reforms have, since 1974, facilitated land use changes and forestry investments. We demonstrate that policy changes which incentivize forestry investments have reduced cultivated agricultural lands and native forest, and concentrated land in the hands of global agribusiness corporations. Compounding these issues, Biobio shows a climatic trend towards aridity coupled with an increasing demand for irrigation. Analyzing these conditions, we argue that the neoliberal globalization of regional agriculture under the context of climatic changes has produced a regional space of increasing vulnerabilities and uneven geographical development in Biobio. We particularly demonstrate that the Chilean mode of agricultural neoliberalization has been conducive to land dispossession—to the detriment of traditional agriculture —and has homogenized the biophysical landscape, replacing traditional crops and native forests with exotic species like pines and eucalyptus. We also examine how local producers are using resistance movements to cope with and contest neoliberal environmental changes. We conclude by evaluating the implications of these spaces of agricultural vulnerabilities and local resistances in the context of uneven geographical development at a regional and global scale.     

Using impacts of deep-level mining to research karst hydrology—a Darcy-based approach to predict the future of dried-up dolomitic springs in the Far West Rand goldfield (South Africa). Part 1: a conceptual model of recharge and inter-compartmental flow

Some of the world’s deepest goldmines are located in the Far West Rand (FWR) goldfield operating below of up to 1.2-km-thick dolomites hosting some of the largest karst aquifers in South Africa. Associated impacts include the dewatering of the overlying karst aquifers as well as linking previously disconnected compartments by mining through aquicludes (dykes). The focus of the study is on predicting groundwater balances in re-watered aquifers after mining ceases as this will determine whether or not associated karst springs that dried-up due to dewatering will ever flow again. Critically revisiting, Swart et al. (Environ Geol 44:751–770, 2003a) who predict that all springs will flow again, this study uses significantly larger data sets and modified assumptions to increase the robustness of findings as the question is crucial for post-closure development. As a first of two papers, this part develops a conceptual model on the mega-compartment concept that predicts a flat water table across all linked compartments that would leave the springs dry. The model identifies the ratio between inflowing surface water (recharge) and underground water losses to downstream compartments via mined-through dykes (‘inter-compartmental groundwater flow’, IGF) as a key factor governing the elevation of the post-mining water table, creating the base for part 2, where the IGF and the post-mining water tables are determined using unique large data sets that have not been evaluated before.     

Using impacts of deep-level mining to research karst hydrology—a Darcy-based approach to predict the future of dried-up dolomitic springs in the Far West Rand goldfield (South Africa). Part 2: predicting inter-compartmental flow and final groundwater tables

Some of the world’s deepest goldmines operate below dolomitic karst aquifers in the Far West Rand (FWR) goldfield, South Africa. Associated impacts include the continuous dewatering of karst aquifers for over six decades and irreversible changes of the hydrogeological setting. Affecting an area of approximately 400 km² by drawing down the water table up to 700 m, these impacts, and the large amounts of data generated in the process, are used as unique research opportunities to better understand the complex karst hydrology. The focus of this study is on predicting final water table elevations in rewatered aquifers after mining ceases taking the fact that mines hydraulically linked previously disconnected aquifers into account. While part 1 of this series develops the conceptual model, this second part utilises large sets of pertinent data to calculate actual flow rates for predicting the fate of dried up springs after mine closure. Following a Darcy-based approach first applied by Swart et al. (Environ Geol 44:751–770, 2003a) it is not only predicted that the springs will flow again but also shown that linear relationships exist between flow rates through a combined system of karst-fractured aquifers overlying the mine void and the associated hydraulic head driving them. This suggests that—at this scale—porous media-based equations can be meaningfully used to predict flow in non-porous media.     

U–Pb zircon ages,field geology and geochemistry of the Kermanshah ophiolite (Iran): From continental rifting at 79 Ma to oceanic core complex at ca. 36 Ma in the southern Neo-Tethys

The geodynamic evolution of the Zagros Mountains of Iran remains obscure. In particular, the time of formation of the Zagros ophiolites and the closure of the Neo-Tethys Ocean are highly controversial. Here we present new precise zircon U–Pb ages that show that the younger part (Sahneh–Kamyaran) of the Kermanshah ophiolite formed at 35.7 ± 0.5 Ma and the older part (Harsin) at 79.3 ± 0.9 Ma. Field relations and geochemical evidence show that the younger Sahneh–Kamyaran part is probably a fossil oceanic core complex, and the older Sahneh part is probably a continental-oceanic transition complex. Both the Sahneh–Kamyaran and Sahneh parts were later emplaced into an accretionary complex. We conclude and infer that the final closure time of the southern Neo-Tethys Ocean was after the Late Eocene. Our data and tectonic model have crucial implications for the geodynamic evolution of the Zagros region.     

Comment on: “Enriched mantle – Dupal signature in the genesis of the Jurassic Ferrar tholeiites from Prince Albert Mountains (Victoria Land, Antarctica)” by Antonini P. et al. (Contributions to Mineralogy and Petrology 136, 1–19; 1999)

18 O values, the magmas retain initial ⁸⁷Sr/⁸⁶Sr Compositions of greater than 0.709 (e.g. Hoefs et al. 1980). Consistent with this is the lack of a radiogenic Os isotope signature in these rocks (e.g. Molzahn et al. 1996) as would be expected with assimilation of continental crust. Comments here are not concerned with the AFC calculations employed to describe the variations within the suite of samples from the Prince Albert mountains studied by Antonini et al., but rather, the extrapolation of these to more primitive compositions. Antonini et al. have revived the possibility that the unusual chemical features of the least evolved low Ti continental flood basalts of the Ferrar Province reflect a crustal-level interplay between mantle-derived magmas and the continental crust. It is argued here that they have not demonstrated their claim. Received: 7 October 1999 / Accepted: 25 January 2000