New water for old? Geology and the long view on water resources

Water used to be regarded as a classic renewable resource, on the reasonable grounds that (in most places, at least) it has a tendency to keep on falling from the sky. However, in recent decades concerns have begun to mount that water is being used consumptively (in some places, at least). This article examines the concept.     

Water chemistry and water quality variation in the Danjiangkou Reservoir, as a function of water management for the Middle Route of South to North Water Divert Project, China

As the diversion dike of the Middle Route of the South to North Water Transfer Project （MRSNWTP）, the water quality and water quantity of Danjiangkou Reservoir is critical to the project. At present, the rates of industrial wastewater treatment and sewage discharge, which belongs to Chinese State Standard in the districts near the reservoir except Shiyan city, are less than 60% and 40% respectively. The point source pollutants will be controlled because of the project after some time, but the non-point source pollutants caused by vegetation degradation and water-soil erosion will not be controlled effectively in a long time. Water samples were collected from the Danjiangkou Reservoir during 2004 and 2005 and analyzed for trace metals, i.e., silver （Ag）, aluminum （Al）, arsenic （As）, barium （Ba）, bismuth （Bi）, calcium （Ca）, cadmium （Cd）, cobalt （Co）, chromium （Cr）, copper （Cu）, iron （Fe）, mercury （Hg）, potassium （K）, lithium （Li）, magnesium （Mg）, manganese （Mn）, molybdenum （Mo）, sodium （Na）, nickel （Ni）, lead （Pb）, antimony （Sb）, selenium （Se）, silicon （Si）, strontium （Sr）, vanadium （V）, zinc （Zn）, chemicophysical parameters and nutrients, i.e., temperature （T）, pH, dissolved oxygen （DO）, turbidity, total suspended solid （TSS）, nitrate/ammonia/ammonium-nitrogen （NO3^-/NH3/NH4^＋-N）, total nitrogen （TN）, dissolved inorganic nitrogen （DIN）, total phosphorus （TP）, potassium permanganate index （IMn）, biochemical oxygen demand （BOD）, dissolved inorganic carbon （HCO3^-）. Our results are water quality belongs to Chinese standard level II, trace metals are low, but they are accumulating, and many of which, i.e., As, Pb, will endanger reservoir water security.     

Reinterpretation of the Ordovician rotations in NW Argentina and Northern Chile: a consequence of the Precordillera collision?

Early Paleozoic paleomagnetic data from NW Argentina and Northern Chile have shown large systematic rotations within two domains: one composed of the Western Puna that yields very large (up to 80°) counter-clockwise rotations, and the other formed by the Famatina Ranges and the Eastern Puna that shows (~40°) clockwise rotations around vertical axes. In several locations, lack of significant rotations in younger rocks constrains this kinematic pattern to have occurred during the Paleozoic. Previous tectonic models have explained these rotations as indicative of rigid-body rotations of large para-autochthonous crustal blocks or terranes. A different but simple tectonic model that accounts for this pattern is presented in which rotations are associated to crustal shortening and tectonic escape due to the collision of the allochthonous terrane of Precordillera in the Late Ordovician. This collision should have generated dextral shear zones in the back arc region of the convergent SW Gondwana margin, where systematic domino-like clockwise rotations of small crustal blocks accommodate crustal shortening. The Western Puna block, bordering the Precordillera terrane to the north, might have rotated counterclockwise as an independent microplate due to tectonic escape processes, in a fashion similar to the present-day relationship between the Anatolia block and the Arabian microplate.     

Intermediate sodium–potassium mica in hydrothermally altered rocks of the Waterloo deposit,Australia: a combined SEM-EMP-XRD-TEM study

Metastable intermediate Na–K mica represents a product of hydrothermal alteration in volcanic rocks from the alteration halo of the Waterloo massive sulfide deposit, Australia. The XRD pattern of this solid solution between paragonite and muscovite is characterized by a rational series of basal reflections with d values intermediate between the end members. Transmission electron microscopy revealed that the intermediate Na–K mica forms thick stacks that belong to a two-layer polytype. Na-rich intermediate Na–K mica typically occurs together with paragonite whereas K-rich intermediate Na–K mica is intergrown with muscovite. The intermediate Na–K mica is interpreted to have formed as a result of the incomplete transformation of K-rich mica to Na-rich mica through dissolution and recrystallization processes driven by compositional changes of the hydrothermal fluids interacting with the volcanic rocks. Alteration must have proceeded under non-equilibrium conditions because the composition of the solid solution falls into the miscibility gap separating paragonite and muscovite.Editorial responsibility: T.L. Grove     

Stable isotopes and noble gases in the Xishimen gold deposit,central North China Craton: metallogeny associated with lithospheric thinning and crust–mantle interaction

Quartz-vein type gold mineralization at Xishimen is a recently discovered gold deposit in the central North China Craton. More than 50 auriferous quartz veins occur in this region within a NNW–SSE-trending fault zone 4600 m in length and 3–10 m wide. Wall rocks are mainly Precambrian tonalite–trondhjemite–granodiorite (TTG) gneisses and associated supracrustals, modified by K-feldspathization and pyrite-phyllic hydrothermal alteration. Based on detailed field and petrographic studies, we identify five episodes of mineralization: pyrite-phyllic stage (I), coarse-grained pyrite-milky white quartz stage (II), fine-grained smoky grey quartz-pyrite stage (III), fine-grained smoky grey quartz-polymetallic sulphide stage (IV), and quartz-carbonate stage (V). We present results of δ³⁴S analysis of sulphide minerals from the different stages which show tightly clustered values in the range of –1.0‰ to 2.1‰, close to those of mantle and meteorite sulphur. Lead isotopic ratios of pyrite from the early to main stages also show restricted ranges with ²⁰⁶Pb/²⁰⁴Pb of 16.289–17.286, ²⁰⁷Pb/²⁰⁴Pb of 15.217–15.453, ²⁰⁸Pb/²⁰⁴Pb of 37.012–38.232, implying lower crustal input. ³He/⁴He and ⁴⁰Ar/³⁶Ar ratios of fluid trapped in pyrite are 0.68 Ra to 1.20 Ra (where Ra is the ³He/⁴He ratio of air = 1.4 × 10^?6) and 540.9–1065, respectively. ³He and ⁴Ar concentrations vary from 10.05 to 18.5 (10^?7 cm³STP/g) and 6.15 to 17.4 (10^?7cm³STP/g), respectively, with calculated mantle helium ranging from 8.47% to 14.96% (average 11.01%). δ¹⁸O_Q and δ¹⁸D_Q values of quartz range from 8.0‰ to 13.2‰ and –101.9‰ to –70.5‰, respectively, with calculated δ¹⁸O_W values of the mineralizing fluid ranging from 1.11‰ to 5.72‰, suggesting the mixing of magmatic aqueous fluid with meteoric water during gold precipitation. We correlate the mixed crust–mantle signature of the ore-forming sources to magmatism and metallogeny associated with Mesozoic inhomogeneous lithosphere thinning in the central North China Craton.     

Stable isotopes （S, Cl） and hydrochemical variations in a karstic ground water system, Guiyang, SW China

A groundwater system in a karstic terrain is easily subject to pollution and its remediation is difficult once contaminated by human activities. The groundwater samples collected in both winter and summer seasons at Guiyang, SW China, show a wide range of variations in chemical composition and dominance of Ca^2＋, Mg^2＋, SO4^2-, and HCO3^- ions. The anthropogenic inputs include Cl^-, NO3^-, SO4^2-, Na^＋, and K^＋, as judged from the relationships between different elemental ratios and sewage samples. Cl^- concentrations of all water samples in the study area vary from 0 to 3.9 mmol/L in winter and are higher than in summer. In most of the samples, SO4^2- concentrations are high, ranging from 0.1 to 11 mmol/U The studies show that the cycling of sulfur plays an important role in controlling water chemistry and fate of contaminants in groundwater. In order to understand the source of SO4^2- and the geochemical cycling of some elements in the karstic groundwater environment, we have carried out a study on the variations of S and Cl isotope compositions, in addition to other isotopic tracers such as ^87Sr/^86Sr and δ^13C studied previously. The δ^37Cl values of the groundwater samples present a seasonal variation, ranging from 0.00‰ to ＋2.03‰ in winter and from -1.46‰ to ＋0.29‰ in summer. The surface water samples show a similar range of variations as observed for groundwater. Two rainwater samples collected at Guiyang have a distinct isotopic signature （mean value is -3‰） compared to the δ^37Cl values reported in literature. These results indicate that ground water is mainly derived from precipitation and suggest a fast recharge of the karst system by surface water.     

Impact of regional geology, land use and flow path on stream water chemistry in a small watershed

Stream water chemistry is dependent on the physical, chemical and biological processes occurring in the watershed. Understanding the governing mechanism of the stream water chemistry in a watershed is the first step for the water quality management. The study area drains a total catchment area of 1.46 km^2 and consists of forest （80%）, upland （15%） and rice paddy field （5%）. The studied area has two distinctive bedrocks, quartzite and schist. We periodically collected the stream water samples at mainstream and tributaries and the pH, electrical conductivity （EC）, alkalinity and the concentrations of cations and anions of the collected stream water samples were determined in the field and laboratory. The all collected water samples were nearly neutral and the EC and concentrations of Na, K, Ca, Sr, Si and HCO3 of the stream water samples collected from the schist terrain had greater values than those from the quartzite terrain. The mainstream running along the boundary of schist and quartzite terrains had the intermediate values of the tributaries. The stream water samples collected in and near the upland showed a high concentration of NO3^- than those of forest regardless the lithology. The stream pathway was also directly reflected on the chemistry of stream water. The stream water drained in the forest of quartzite terrain had the lowest values of alkalinity, EC and concentrations of cations and anions but the stream water drain in the upland of schist terrain had the highest values of EC and concentrations of cations and anions, especially NO3^-.     

Correlated δ18O and [Ti] in lunar zircons: a terrestrial perspective for magma temperatures and water content on the Moon

Zircon grains were separated from lunar regolith and rocks returned from four Apollo landing sites, and analyzed in situ by secondary ion mass spectrometry. Many regolith zircons preserve magmatic δ¹⁸O and trace element compositions and, although out of petrologic context, represent a relatively unexplored resource for study of the Moon and possibly other bodies in the solar system. The combination of oxygen isotope ratios and [Ti] provides a unique geochemical signature that identifies zircons from the Moon. The oxygen isotope ratios of lunar zircons are remarkably constant and unexpectedly higher in δ¹⁸O (5.61 ± 0.07 ‰ VSMOW) than zircons from Earth’s oceanic crust (5.20 ± 0.03 ‰) even though mare basalt whole-rock samples are nearly the same in δ¹⁸O as oceanic basalts on Earth (~5.6 ‰). Thus, the average fractionation of oxygen isotopes between primitive basalt and zircon is smaller on the Moon [Δ¹⁸O(WR-Zrc) = 0.08 ± 0.09 ‰] than on Earth (0.37 ± 0.04 ‰). The smaller fractionations on the Moon suggest higher temperatures of zircon crystallization in lunar magmas and are consistent with higher [Ti] in lunar zircons. Phase equilibria estimates also indicate high temperatures for lunar magmas, but not specifically for evolved zircon-forming melts. If the solidus temperature of a given magma is a function of its water content, then so is the crystallization temperature of any zircon forming in that melt. The systematic nature of O and Ti data for lunar zircons suggests a model based on the following observations. Many of the analyzed lunar zircons are likely from K, rare earth elements, P (KREEP)-Zr-rich magmas. Zircon does not saturate in normal mafic magmas; igneous zircons in mafic rocks are typically late and formed in the last most evolved portion of melts. Even if initial bulk water content is moderately low, the late zircon-forming melt can concentrate water locally. In general, water lowers crystallization temperatures, in which case late igneous zircon can form at significantly lower temperatures than the solidus inferred for a bulk-rock composition. Although lunar basalts could readily lose H₂ to space during eruption, lowering water fugacity; the morphology, large size, and presence in plutonic rocks suggest that many zircons crystallized at depths that retarded degassing. In this case, the crystallization temperatures of zircons are a sensitive monitor of the water content of the parental magma as well as the evolved zircon-forming melt. If the smaller Δ¹⁸O(zircon–mare basalt) values reported here are characteristic of the Moon, then that would suggest that even highly evolved zircon-forming magmas on the Moon crystallized at higher temperature than similar magmas on Earth and that magmas, though not necessarily water-free, were generally drier on the Moon.     

Integrating sustainable development and economic restructuring: a role for regulation theory?

Despite the growing importance of environmental issues within international and national economic policies, little attention has been paid to these issues in work on economic restructuring. However, the increasing adoption of the concept of sustainable development as a means to resolve conflict between the economy and the environment has major implications for the form and direction of economic restructuring. In this paper it is therefore argued that the growing adoption of sustainable development as a central guiding principle for economic development necessitates the incorporation of environmental issues into work on economic restructuring. The limited amount of existing work linking the environment with economic restructuring is criticized and it is suggested that there is considerable potential to use regulation theory to combine debates on economic restructuring and sustainable development.     

Sediment recycling and crustal growth in the Central Asian Orogenic Belt: Evidence from Sr–Nd–Hf isotopes and trace elements in granitoids of the Chinese Altay

Felsic igneous rocks are common constituents of volcanic arcs, and contain valuable information about subduction-related magmatism. In this study we investigate nine granitoids with S-type volcanic arc affinity from the Chinese Altay, emplaced from 507 to 391 Ma in an active subduction zone during the early–middle Paleozoic. These granitoids are characterized by moderate to high SiO₂ contents (61.01–75.30 wt.%), moderate total alkalis (Na₂O + K₂O, 3.43–7.64 wt.%), and high Al₂O₃ contents (13.29–17.18 wt.%). Negative εNd(t) values (− 6.1 to − 1.0), the wide range of εHf(t) values (− 7.0 to + 9.0), and enrichment of LILEs such as Pb, Th and U, all suggest that the granitoids were probably derived from the partial melting of subducting oceanic sediments and the associated mantle wedge. This inference is further supported by the Nd-isotope data. The high initial ⁸⁷Sr/⁸⁶Sr ratios (0.703963–0.719428), low Ba/Th ratios (7.00–118.93), and uniformly negative εNd(t) values (− 6.1 to − 1.0) indicate that slab-derived aqueous fluids were vital in generating the initial magma of these granitoids, and assimilation played only a minor role. Our data demonstrate that residual zircon retains a substantial amount of Hf during the partial melting of oceanic sediments, therefore, Hf may not be an effective tracer for the input of recycled sediments. We conclude that sediment recycling played an important role in the generation of arc magmatism and the growth of the Central Asian Orogenic Belt (CAOB).     

First data on the isotopes of Sm—Nd and Sr for Cretaceous—Paleogene granitoids of primors’e and some problems of their genesis

Doklady Earth Sciences -     

U–Pb zircon chronology,geochemistry and isotopes of the Changyi banded iron formation in the eastern Shandong Province: Constraints on BIF genesis and implications for Paleoproterozoic tectonic evolution of the North China Craton

The Changyi banded iron formation (BIF) in the eastern North China Craton (NCC) occurs within the Paleoproterozoic Fenzishan Group. The BIF shows alternating quartz-rich light and magnetite-rich dark bands with magnetite (15–65 vol.%), quartz (25–65 vol.%) and amphibole (15–30 vol.%) constituting the major minerals. Minor garnet, epidote, chlorite, calcite, biotite and pyrite occur locally. The BIF bands are interlayered with amphibolite, hornblende gneiss, biotite quartz schist, garnet biotite schist, biotite gneiss and leptynite, and are intruded by granites. LA-ICP-MS U–Pb dating on zircons separated from the BIF bands and the wallrocks constrains the depositional age as 2240–2193 Ma and metamorphic age as ~ 1864 Ma. The dominant composition of SiO₂ + Fe₂O₃^T (average value of 92.3 wt.%) of the BIF bands suggests their formation mainly through chemical precipitation. However, the widely varying contents of major elements such as Al₂O₃ (0.58–6.99 wt.%), MgO (1.00–3.86 wt.%), CaO (0.22–4.19 wt.%) and trace elements such as Rb (2.06–40.4 ppm), Sr (9.36–42.5 ppm), Zr (0.91–23.6 ppm), Hf (0.04–0.75 ppm), Cr (89.1–341 ppm), Co (2.94–30.4 ppm), and Ni (1.43–52.0 ppm) clearly indicate the incorporation of clastics, especially continental felsic clastics, as also confirmed by the presence of ancient detrital zircons in the BIF bands. When normalized against Post Archean Average Shale (PAAS), the seawater-like signatures of REE distribution patterns, such as LREE depletion, positive La and Y anomalies, and superchondritic Y/Ho ratios (average value of 36.3), support the deposition in seawater. Strong positive Eu anomalies (Eu/Eu*_PAAS = 1.14–2.86) also suggest the participation of hydrothermal fluids. In addition, the sympathetic correlation between Cr, Co and Ni as well as the Co + Ni + Cu vs. ∑ REE and the Al₂O₃ vs. SiO₂ relations further indicates that the iron and silica mainly originated from hydrothermal fluids. Combined with regional geological investigation and protolith restoration of the wallrocks, a continental rift environment is suggested for the Changyi BIF deposition. The appearance of negative Ce_PAAS anomalies might suggest the influence of the Great Oxidation Event at the time of deposition. The Changyi BIF witnessed the major Paleoproterozoic rifting–collision events in the NCC and their unique distribution in the NCC contrasts with other examples elsewhere in the world.     

Facing climatic and anthropogenic changes in the Mediterranean basin: What will be the medium-term impact on water stress?

The Mediterranean basin has been identified as one of the world's most vulnerable regions to climatic and anthropogenic changes. A methodology accounting for the basin specific conditions is developed to assess the current and future water stress state of this region. The medium-term evolution of water stress is investigated using climatic scenarios and a water-use scenario based on efficiency improvements following the recommendations of the Mediterranean Strategy for Sustainable Development. Currently, the southern and eastern rims are experiencing high to severe water stress. By the 2050 horizon, a 30–50% decline in freshwater resources is simulated over most of the Mediterranean basin. While total water withdrawals would stabilize, or even decrease (10–40%), in several northern catchments, they would double in southern and eastern catchments. These changes should significantly increase water stress over the Mediterranean basin and exacerbate the disparities between rims.     

Petrology,geochemistry and zircon U–Pb and Lu–Hf isotopes of the Cretaceous dykes in the central North China Craton: Implications for magma genesis and gold metallogeny

The Trans-North China Orogen (TNCO), a Paleoproterozoic suture that amalgamates the Western and Eastern Blocks of the North China Craton (NCC), witnessed extensive magmatism and metallogeny during Mesozoic, associated with intraplate tectonics and differential destruction of the cratonic lithosphere. Here we investigate a suite of porphyry dykes surrounding the Mapeng batholith in the Fuping Complex within the TNCO in relation to the Mesozoic gold and molybdenum mineralization. The major element chemistry of these dykes show a range of SiO₂ (57.92 to 69.47 wt.%), Na₂O (3.20 to 4.77 wt.%), K₂O (3.12 to 4.60 wt.%) and MgO (0.51 to 3.67 wt.%), together with high concentration of LREE and LILE, and relatively low contents of HREE and HFSE. The rocks display (La/Yb)_N = 13.53–48.11, negative Nb, Ta, Th, U and Zr anomalies, and distinctly positive Ba, K and Sm anomalies. The mineralogy and geochemistry of the porphyry dykes indicate the rocks to be high-K calc-alkaline, and I-type, with adakitic features similar to those of the adjacent Mapeng batholith. The source magma for these rocks was derived from a mixture of reworked ancient continent crust and juvenile mantle materials. The zircon U–Pb data from these rocks show ages in the range of 124 to 129 Ma, broadly coinciding with the emplacement age of the Mapeng intrusion. The inherited zircons of ca. 2.5, 2.0 and 1.8 Ga in the dykes represent capture from the basement rocks during melting. The zircon Lu–Hf isotopic compositions show negative ε_Hf(t) values varying from − 27.8 to − 11.3, with Hf depleted model ages (t_DM) ranging from 1228 Ma to 1918 Ma and Hf crustal model ages (t_DM^C) of 1905 Ma to 2938 Ma, suggesting that the Mesozoic magmatism and associated metallogeny involved substantial recycling of ancient basement rocks of the NCC. We present an integrated model to evaluate the genesis of the porphyry systems and their relation to mineralization. We envisage that these dykes probably acted as stoppers (impermeable barriers) that prevented the leakage and run-off of the ore-bearing fluids, and played a key role in concentrating the gold and molybdenum mineralization.     

Ultrahigh-temperature mafic granulite in the Huai’an Complex,North China Craton: Evidence from phase equilibria modelling and amphibole thermometers

The Huai’an Complex in the north-western Trans-North China Orogen, North China Craton is recognized to have undergone high-pressure metamorphism with controversial ages. Two mafic granulite samples (17HT13 and 16HT22) from Huangtuyao of the Huai’an Complex are documented for metamorphism based on petrography, mineral chemistry, phase equilibria modelling and zircon dating. The rocks comprise garnet, clinopyroxene, orthopyroxene, amphibole, plagioclase and ilmenite. They show clockwise P-T paths involving the pre-T_max decompressional heating, the T_max and the post-T_max cooling stages. The pre-T_max decompressional heating is revealed by the core-rim/mantle anorthite-ascending zoning in coarse-grained plagioclase. The T_max stage is constrained to 8.5–10.5 kbar/980–1010 °C (17HT13) and 7.5–9.5 kbar/1000–1030 °C (16HT22) by the high Ti content of amphibole, and the anorthite content of coarse-grained plagioclase rims/mantles and fine-grained plagioclase cores. These temperatures are slightly higher than the results of amphibole thermometers (∼940–980 °C). The post-T_max cooling is defined by the later growth of amphibole and some conventional geothermobarometers. Because it is dominated by temperature with ilmenite present, the Ti content of amphibole is proposed as a reliable thermometer, and the Ti-rich amphibole with Ti > 0.28 p.f.u. or TiO₂ > 2.4–2.6 wt% is indicative of ultrahigh-temperature (>900 °C, UHT) conditions. The anorthite content of plagioclase is also significant in confining peak temperatures for UHT granulite but requires defining proper water content. Zircon dating for 17HT13 yields an upper intercept age of 1910 ± 35 Ma, representing the cooling of UHT granulite. We conclude that the Huai’an Complex may have at least locally undergone UHT metamorphism at ∼1.92–1.91 Ga after high-pressure granulite metamorphism at ∼1.95 Ga, similar to the Jining Complex. Therefore, the Huai’an and Jining Complexes share the same tectonic evolution involving ∼1.95 Ga crustal thickening, ∼1.92–1.91 Ga extension with regional or local UHT metamorphism, and subsequent cooling and uplifting.     

Chemical and strontium isotopic characteristics of shallow groundwater in the Ordos Desert Plateau,North China: Implications for the dissolved Sr source and water–rock interactions

In this study, the chemical and Sr isotopic compositions of shallow groundwater and rainwater in the Ordos Desert Plateau, North China, and river water from the nearby Yellow River, are investigated to determine the dissolved Sr source and water–rock interactions, and quantify the relative Sr contribution from each end-member. Three groundwater systems have been identified, namely, GWS-1, GWS-2 and GWS-3 according to the watershed distribution in the Ordos Desert Plateau. Ca²⁺ and Mg²⁺ are the most dominant cations in GWS-1, while Na⁺ is dominant in GWS-3. In addition, there is more SO₄²⁻ and less Cl⁻ in GWS-1 than in GWS-3. The shallow groundwater in GWS-2 seems to be geochemically between that in GWS-1 and GWS-3. The ⁸⁷Sr/⁸⁶Sr ratios of the shallow groundwater are high in GWS-1 and GWS-2 and are low in GWS-3. By geochemically comparing the nearby Yellow River, local precipitation and deep groundwater, the shallow groundwater is recharged only by local precipitation. The ionic and isotopic ratios indicate that carbonate dissolution is an important process controlling the chemistry of the shallow groundwater. The intensity of the water–rock interactions varies among the three groundwater systems and even within each groundwater system. Three end-members controlling the groundwater chemistry are isotopically identified: (1) precipitation infiltration, (2) carbonate dissolution and (3) silicate weathering. The relative Sr contributions of the three end-members show that precipitation infiltration and carbonate dissolution are the primary sources of the shallow groundwater Sr in GWS-3 whereas only carbonate dissolution is responsible for the shallow groundwater Sr in GWS-1 and GWS-2. Silicate weathering seems insignificant towards the shallow groundwater's chemistry in the Ordos Desert Plateau. This study is helpful for understanding groundwater chemistry and managing water resources.     

The petrology of a complex sodic and sodic–calcic amphibole association and its implications for the metasomatic processes in the jadeitite area in northwestern Myanmar,formerly Burma

In the Myanmar jadeitite area of Pharkan, amphibole felses occur between jadeitites and serpentinized dunites. These so-called amphibole fels boundary zones were studied optically and by electron microprobe, and found to include the six amphibole species magnesiokatophorite (Mg-kat), nyböite (Nyb), eckermannite (Eck), glaucophane (Gln), richterite (Rich) and winchite (Win). In most samples, the two main amphibole species Mg-kat and Eck coexist with amphiboles containing variable amounts of components of the remaining four species, as well as with the clinopyroxenes jadeite (Jd), omphacite (Omp) and kosmochlor (Ko). However, Mg-kat, Nyb and Eck are also present as separate phases as well as in zoned porphyroblasts with Mg-kat in the core, Nyb in the inner rims, and Eck in the outer rims. The analytical data on such zoned amphiboles reveal that the chemistry changes from core to inner rim by virtue of the substitution NaAlCa _-1Mg _-1 (glaucophane vector), and from the inner to the outer rim along MgSiAl _-1Al _-1 (tschermak vector). The overall substitution from core to outer rim is, therefore, along NaSiCa _-1Al _-1 (plagioclase vector). Based on the Si content, three groups can be distinguished within Eck: Eck coexisting with Nyb has low Si contents of <7.6 a.p.f.u., Eck rimming Nyb has higher Si contents of 7.6–8.0 a.p.f.u., and fine-grained Eck in the matrix has Si contents of 7.9–8.0 a.p.f.u. Plotting the amphibole analyses in a compositional volume with the axes (Na+K) in A, Na in M(4), and tetrahedral Si shows that three groups of amphibole compositions can be distinguished, one being subdivided into three subsets. Group A contains Rich and Mg-kat, B comprises of Win and Gln, whereas the subsets C can be defined as follows: C1: high-Na amphiboles with low tetrahedral Si; these are mainly amphiboles from the Eck field but overlap with the two fields of Gln and Win; C2: high-Na and low-Si Ecks overlapping to high-Si Nybs; this group is midway between Eck and Nyb end members; C3: high-Na Mg-kats. Textural observations indicate three stages of sodic and sodic–calcic amphibole growth: stage 1 are amphiboles of group A (Mg-kat+Rich), stage 2 are amphiboles of group C2 (Nyb+Eck with Si<7.6 a.p.f.u.), and stage 3 are amphiboles of groups C1 and B (Eck with Si>7.6 a.p.f.u., +Gln+Win). Based on the subdivision into the compositional groups A–C, the only hint to a miscibility gap is provided by the large gap in the (Na+K) content on the A site which may point to a possible solvus in the system Eck–Win. Overall, the amphiboles investigated here show discontinuities in their growth compositions, rather than miscibility gaps. Textural observations suggest amphibole formation during fluid infiltration in the contact zone between the jadeitite bodies and the surrounding peridotite under high-pressure conditions (>1.0 GPa) and rather low temperatures of about 250–370 °C. Based on compositional trends within the amphiboles as well as phase-equilibrium constraints between amphibole and coexisting pyroxene solid solutions, the chemical composition of zoned amphibole porphyroblasts indicates two growth episodes—increasing pressures from stage 1 to stage 2 lead to the formation of Nyb from Mg-kat, and subsequently decreasing pressures lead to the formation of stage 3 Eck from Rich.