Abstract The distinctive hydrology and landforms of karst create a very special environment. Although several types of karst have been identified worldwide, a common thread is the dominantly subterranean drainage. The paucity of water flowing at the surface, a consequence of rapid infiltration underground through a network of discontinuities in the soluble rock mass, results in two important but contrasting points: the considerable value of karst water resources (representing about 25% of the drinkable supply in the world) is strongly counteracted by the ease with which human activities can negatively impact this precious resource. The same narrow discontinuities, and the larger dissolution conduits and karst caves, are the main pathways through which potential pollutants may travel swiftly to regional groundwater bodies, or directly to springs. Contaminants can be introduced by means of dispersed infiltration as well as from point sources and are frequently transmitted with minimal filtering. This example, just one of the many natural and/or anthropogenic hazards that may affect karst areas, illustrates the fragility of karst environments. Their high vulnerability is further expressed by a very simple concept that is true for many other environments but probably shows its best evidence in karst: it is very easy to damage or destroy natural resources but restoration to a pristine situation is an extremely difficult and commonly impossible, task. Where some degree of remediation is possible, the economic cost is commonly very high. Since the early 1960s there has been a great deal of progress in understanding the processes and landforms

Abstract The Ertsberg-Grasberg district hosts two giant Cu-Au (± Mo)-rich porphyry and skarn-hosted Cu systems that formed between 3.3 and 2.5 Ma. These Cu-Au systems are associated with two separate K-rich dioritic intrusions, the Grasberg Igneous Complex and the Ertsberg Intrusive Complex, which were shallowly emplaced into a sedimentary sequence of Tertiary carbonate and Jurassic-Cretaceous siliciclastic rocks. The district is located near the crest of the Central Range of western New Guinea, in the easternmost Indonesian province of Papua (formerly Irian Jaya). Economic mineralization in each of these systems is vertically continuous over at least 1,500 m. Using a non-economic cutoff grade of 0.1% Cu, the Grasberg-related system contains 7.5 billion tonnes (grading 0.70% Cu and 0.64 ppm Au) in two deposits, the Grasberg porphyry system and the Kucing Liar skarn. At the same 0.1% Cu cutoff, the Ertsberg-related system contains 3.6 billion tonnes (grading 0.60% Cu and 0.44 ppm Au) in four deposits, the Ertsberg skarn, the Ertsberg East skarn system, the Dom skarn, and the Big Gossan skarn. A significant aspect of these orebodies is their ability to deliver a large tonnage of much higher than these average Cu and Au grades, which is required to offset the high costs of mining in the challenging environment in which they are exploited. The Ertsberg, Dutch for “ore mountain,” was discovered in 1936. Freeport evaluated the prospect in the 1960s, and began mine development in 1969. Discovery of the Ertsberg East skarn and the Dom skarn ore-bodies quickly followed initial development in the district. The Grasberg deposit was discovered by exploration drilling in 1988, targeting Au mineralization in an intensely quartz-magnetite stockwork-veined outcrop that had been depleted of its Cu due to supergene leaching. This was followed by discovery of the high-grade Big Gossan skarn in 1992 and the massive Kucing Liar skarn in 1994. Geologic studies have shown that the Central Range was produced by collisional tectonism that resulted when the northern edge of the Australian plate entered and jammed the subduction zone beneath the Melanesian oceanic arc. Magmas were generated during the breakoff of the oceanic end of the Australian plate as a result of decompression melting of asthenospheric and lithospheric mantle, which upwelled into the subterranean rift. This short episode (4.4–2.6 Ma) of intermediate-composition magmatism formed the district's porphyry Cu deposits. Magmatism and mineralization occurred in a structural corridor dominated by left-lateral strike-slip reactivation of the preexisting compressional regime faults, implying a tensional environment as a significant control to shallow emplacement. Pull-apart connections between strike-slip faults created pathways for magma ascent and the focused flow of magmatic fluids. Porphyry-type mineralization developed where the fluids ascended through igneous rocks, and skarns developed where they interacted with carbonate strata, especially impure dolostones. Porphyry-style alteration follows typical patterns of a potassic core grading outward into phyllic alteration, and surrounded by a propylitic halo at the shallower levels of the system. Advanced argillic alteration is weakly represented in the igneous rocks. Stockwork vein systems form in the central high-temperature, potassic-altered zones and are the locus of the highest Cu and Au grades in the porphyry orebodies. High Au/Cu ratios (>1 g/t:%) are characteristic of ores formed within these central high grade zones; ratios diminish outward from the center of the systems more sharply than does the Cu grade. The overall Au/Cu ratio at Grasberg is 1 and is 1.3 in the porphyry-hosted ores at Ertsberg East skarn system. Chalcopyrite is the dominant Cu mineral throughout the potassic zones and bornite increases with depth. The majority of the Au is contained as free inclusions within these two Cu minerals, and within the potassic zone; covellite dominates in the phyllic zone with lesser chalcopyrite. Gold associations in the phyllic zone are complex. Where covellite dominates the Cumineral assemblage, Au is most commonly contained within pyrite or as free grains within the silicate rock matrix. Skarn alteration mineralogy is strongly controlled by the host stratigraphy and is similar at both complexes. Prograde skarn mineralogy in the calcareous Kais and Faumai formations is dominated by monticellite and diopside, with lesser forsterite. Forsterite plus diopside dominate the dolomitic lower Waripi formation and the limestone member of the Ekmai formation. Massive magnetite mineralization is contemporaneous with pro-grade alteration, preferentially replacing dolostone beds and areas of apparent high fluid flow. Retrograde alteration is represented by chlorite-serpentine-talc in the upper limestone formations, and by actinolite-tremolite-phlogopite-talc-serpentine-chlorite plus calcite in the lower, more dolomitic formations. Chalcopyrite dominates over bornite in the magnetite-poor ores in the Ertsberg East skarn system, whereas bornite dominates in magnetite-rich ores. At Kucing Liar, chalcopyrite dominates over bornite, even within the magnetite-rich ores, but is replaced by covellite + pyrite on all orebody margins. Copper and Au are concentrated within magnetite replacement bodies, where present, in both of these skarns; Au/Cu ratios are ∼0.5 at Ertsberg East skarn system and ∼1 at Kucing Liar.

Abstract Ambient temperature freshwater carbonates precipitate as surface deposits within karstic stream, lake and swamp environments (tufas) and in subterranean situations (speleothems), where they line vadose caves and fracture systems. Although physico-chemical mineral precipitation contributes significantly to both kinds of deposit, there is a clear spatial association between the development of tufa deposits and the occurrence of microbial biofilms. This fact, and the recent discovery that the occurrence of certain heterotrophic bacteria promote precipitation onto the surface of stalactites ( Cacchio et al. 2004 ), strongly implicates a degree of microbial influence in the calcite precipitation process, regardless of the environmental context. To add to the inherent complexity of these systems, there is considerable interplay between biological and physical processes to consider. Water velocity and turbulence will strongly affect biofilm colonization and may damage the community, thereby affecting carbonate precipitation rates, in addition to regulating important kinetic limitations on precipitation via modifications of the calcium ion delivery rate. Exchange of CO 2 gas at the air–water interface is an important conditioner for precipitation in vadose systems but will also occur within surface systems as a consequence of photosynthesis. It is only by considering karst hydrological systems holistically that these processes can be untangled. Tufas and speleothems share the same soil-derived meteoric water supply, represent zones of deposition of calcium ions chemically eroded from the same geological sources and produce laminated deposits which are superficially similar. In passing from cave environments via resurgences (Fig. 1) into surface waterways, individual packages of water pass down

ABSTRACT The exceptional groundwater community inhabiting the karstic Edwards-Trinity Aquifer system in central Texas has inspired generations of biologists seeking to understand diversification in an extreme environment. Since the late 1990s, molecular genetic tools have increasingly been used to uncover hidden diversity and infer the evolutionary history of groundwater species inhabiting the Edwards-Trinity system. The field of phylogeography—the study of the spatial distribution of genealogical lineages within and among intraspecific populations and closely related species—has provided unparalleled insight into patterns of Edwards-Trinity groundwater biodiversity. Similar to other global groundwater biodiversity hotspots, phylogeographic studies in the Edwards-Trinity Aquifer system have documented exceptionally high levels of endemism and strong population structure due to isolation across naturally fragmented habitat. Cryptic species (two or more morphologically similar but genetically distinct species) have been discovered in a number of phylogeographic investigations, including Eurycea salamanders, Dionda minnows, and Stygobromus amphipods. A number of these species are threatened or endangered with extinction due to habitat loss and degradation resulting from urbanization. Accurately delimiting species boundaries has had significant implications for biodiversity and groundwater conservation in the Edwards-Trinity region because the Endangered Species Act has been used to regulate unrestricted groundwater withdrawal in the eastern Edwards Aquifer where listed species are found. New developments in deoxyribonucleic acid (DNA) sequencing technology coupled with advancements in model-based inference will provide powerful tools for furthering our understanding of Edwards-Trinity biodiversity and predicting its response to a rapidly changing environment.