The influence of porcupine diggings upon annual vegetation on a north-facing hillslope in the Negev Desert, Israel, has been observed for some 10 years. It was found that within the porcupine diggins there are changes over time in terms of species richness, plant density and plant biomass, and that such changes take place in three stages. During the initial growing season (stage 1), species richness, plant density and plant biomass are lower than in the surrounding non-disturbed area, followed by progressive plant succession. Subsequently, a maximum level is attained when a dig becomes 50-60% filled in (stage 2). As the extent of filling exceeds 60%, a decrease in species richness, plant density and plant biomass is observed (stage 3). This process concurs with models derived in other ecosystems with animals that create surface disturbances. The role of porcupine diggings as a model of disturbance and recovery is discussed.

U-Pb ages, trace element content and oxygen isotope ratios of single zircons from five plagiogranite intrusions of the Troodos ophiolite were measured in order to determine their crystallization age and assess the importance of fractional crystallization versus crustal anatexis in their petrogenesis. The results indicate that oceanic magmatism in Troodos took place at 94.3 ± 0.5 Ma, about three Myr older than previously recognized. Later hydrothermal alteration has affected most of Troodos plagiogranitic rocks, resulting in growth of new zircon and/or partial alteration of zircon domains, causing slightly younger apparent crystallization ages. The new age inferred for seafloor spreading and ocean crust accretion in Troodos nearly overlaps that of the Semail ophiolite in Oman (95-96 Ma), strengthening previous indications for simultaneous evolution of both ophiolites in similar tectonic settings. Average δ18O(Zrn) values in the Troodos plagiogranites range between 4.2 and 4.8‰. The lower values in this range are lower than those expected in equilibrium with mantle-derived melt (5.3 ± 0.6‰), indicating substantial contribution from hydrothermally-altered, deep-seated oceanic crust in most of the Troodos plagiogranite intrusions. The inferred high percentage of crustal component is consistent with the existence of a shallow axial magma chamber, typical of fast spreading MOR settings, within the Troodos slow-spreading ridge environment. This apparent contradiction may be reconciled by episodically intense magmatism within an otherwise slow, magmatically-deprived spreading axis.

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Collision‐related granitoid batholiths, like those of the Hercynian and Himalayan orogens, are mostly fed by magma derived from metasedimentary sources. However, in the late Neoproterozoic calcalkaline (CA) batholiths of the Arabian–Nubian Shield (ANS), which constitutes the northern half of the East African orogen, any sedimentary contribution is obscured by the juvenile character of the crust and the scarcity of migmatites. Here, we use paired in situ LASS‐ICP‐MS measurements of U–Th–Pb isotope ratios and REE contents of monazite and xenotime and SHRIMP‐RG analyses of separated zircon to demonstrate direct linkage between migmatites and granites in the northernmost ANS. Our results indicate a single prolonged period of monazite growth at 640–600 Ma, in metapelites, migmatites and peraluminous granites of three metamorphic suites: Abu‐Barqa (SW Jordan), Roded (S Israel) and Taba–Nuweiba (Sinai, Egypt). The distribution of monazite dates and age zoning in single monazite grains in migmatites suggest that peak thermal conditions, involving partial melting, prevailed for c. 10 Ma, from 620 to 610 Ma. REE abundances in monazite are well correlated with age, recording garnet growth and garnet breakdown in association with the prograde and retrograde stages of the melting reactions, respectively. Xenotime dates cluster at 600–580 Ma, recording retrogression to greenschist facies conditions as garnet continued to destabilize. Phase equilibrium modelling and mineral thermobarometry yield P–T conditions of ~650–680°C and 5–7 kbar, consistent with either water‐fluxed or muscovite‐breakdown melting. The expected melt production is 8–10 vol.%, allowing a melt connectivity network to form leading to melt segregation and extraction. U–Pb ages of zircon rims from leucosomes indicate crystallization of melt at 610 ± 10 Ma, coinciding with the emplacement of a vast volume of CA granites throughout the northern ANS, which were previously considered post‐collisional. Similar monazite ages (c. 620 Ma) retrieved from the amphibolite facies Elat schist indicate that migmatites are the result of widespread regional rather than local contact metamorphism, representing the climax of the East African orogenesis.

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