Inferring land use from mobile phone activity

Understanding the spatiotemporal distribution of people within a city is crucial to many planning applications. Obtaining data to create required knowledge, currently involves costly survey methods. At the same time ubiquitous mobile sensors from personal GPS devices to mobile phones are collecting massive amounts of data on urban systems. The locations, communications, and activities of millions of people are recorded and stored by new information technologies. This work utilizes novel dynamic data, generated by mobile phone users, to measure spatiotemporal changes in population. In the process, we identify the relationship between land use and dynamic population over the course of a typical week. A machine learning classification algorithm is used to identify clusters of locations with similar zoned uses and mobile phone activity patterns. It is shown that the mobile phone data is capable of delivering useful information on actual land use that supplements zoning regulations.Comment: To be presented at ACM UrbComp201

Development of scenarios for land cover, population density, impervious cover, and conservation in New Hampshire, 2010–2100

Future changes in ecosystem services will depend heavily on changes in land cover and land use, which, in turn, are shaped by human activities. Given the challenges of predicting long-term changes in human behaviors and activities, scenarios provide a framework for simulating the long-term consequences of land-cover change on ecosystem function. As input for process-based models of terrestrial and aquatic ecosystem function, we developed scenarios for land cover, population density, and impervious cover for the state of New Hampshire for 2020–2100. Key drivers of change were identified through information gathered from six sources: historical trends, existing plans relating to New Hampshire’s land-cover future, surveys, existing population scenarios, key informant interviews with diverse stakeholders, and input from subject-matter experts. Scenarios were developed in parallel with information gathering, with details added iteratively as new questions emerged. The final scenarios span a continuum from spatially dispersed development with a low value placed on ecosystem services (Backyard Amenities) to concentrated development with a high value placed on ecosystem services (the Community Amenities family). The Community family includes two population scenarios (Large Community and Small Community), to be combined with two scenarios for land cover (Protection of Wildlands and Promotion of Local Food), producing combinations that bring the total number of scenarios to six. Between Backyard Amenities and Community Amenities is a scenario based on linear extrapolations of current trends (Linear Trends). Custom models were used to simulate decadal change in land cover, population density, and impervious cover. We present raster maps and proportion of impervious cover for HUC10 watersheds under each scenario and discuss the trade-offs of our translation and modeling approach within the context of contemporary scenario projects

Titanite zoning and magma mixing

Titanite is a calcium titanium silicate accessory mineral that serves as a sink for trace elements, especially the rare-earth elements and the high-field strength elements (Cerny and Rivadisa.L 1972; Groat, Carter et al. 1985; Enami, Suzuki et al. 1993; Perseil and Smith 1995; Della Ventura, Bellatreccia et al. 1999; Piccoli, Candela et al. 2000). It is also characterised by very sluggish diffusion of these elements, and as such it has the ability to resist most sub-solidus alteration. These characteristics make titanite a prime candidate for the ability to preserve a record of the petrogenetic processes which formed the igneous rocks in which it is found. In order to assess titanite’s ability to serve as a petrogenetic tool, a textural and geochemical study of titanite from different igneous environments was undertaken. The Ross of Mull Granite is an igneous complex located on the south west coast of the Isle of Mull, Scotland. It is a Caledonian age pluton that displays evidence of magma-mixing processes at depth and also contains notable amounts of titanite. Samples of different host granite and diorite enclave lithologies and relationships were documented and collected in order to asses the ability of titanite to retain evidence of magma-mixing processes within its compositional zoning. Titanite from the Ross of Mull Granite displays a large variety of textural features, both with respect to crystal shape and compositional zoning. The variation of the trace elements observed in titanite is a direct reflection of the compositional zoning pattern. Melts that are enriched in particular trace elements pass on that signature to the titanites. If melts of significantly contrasting chemistries mix or mingle, then titanite may record any significant instance of trace element diffusion between the melts. More importantly, there doesn’t need to be a transfer of trace elements between mingling/mixing melts for titanite to record evidence of the interaction. If the melts are of significantly different oxygen fugacities, then titanite may become destabilised and partially dissolve. This dissolution may only be temporary, but it may be difficult to tell if it was a product of increasing heat of the melt of if it was due to a change in oxygen fugacity. Titanite however, may record evidence of the cause of dissolution based on the nature of re-growth. As shown by some of the titanites within the Ross of Mull Granite, re-growth following a period of dissolution may be attributed to a change in oxygen fugacity if the new titanite growth is characterised by unusually low REE content. This is related to the nature of trace element incorporation in the titanite structure; REE are taken up due to coupled substitution mechanisms involving tetravalant Al and Fe. If a melt becomes reduced then the activity of ferric Fe will also be reduced, thus inhibiting the ability of titanite to take up REE by affecting the activity of the coupled substitution (Wones 1989; Piccoli, Candela et al. 2000). Titanite from the ROMG is largely characterised by compositional zoning that reflects the trace element chemistry of one of the end-member lithologies (host granite or dioritic enclaves), or has compositional zoning that reflects the changing conditions of the magmatic environment, namely: changes in melt composition, changes in temperature and pressure and changes in oxidation of the magma. In the case of the ROMG, all of these changes were wholly, or in part, brought about by magma mixing processes. Another way in which titanite reflects processes of petrogenesis is that it has been found to reflect the degree of homogenisation of the melt from which it has crystallised. To further asses the ability of titanite serve as a petrogenetic tool, a study was made of the characteristics of titanite from the volcanic environment. The Fish Canyon Tuff, from the San Juan volcanic field, Colorado, USA, was chosen as a suitable candidate for study due to its well documented nature; it is the largest known pyroclastic eruption to be documented. The Fish Canyon tuff also contains numerous phenocrysts of titanite. Eruption of the Fish Canyon Tuff is thought to have been brought about by the thermal rejuvenation of a batholith-sized magma chamber which had previously cooled to a rigid crystal mush (Bachmann and Bergantz 2003). The main conclusion from the study of titanites from the Fish Canyon Tuff and is that evidence for the thermal rejuvenation of the magma chamber by a mafic melt prior to eruption is preserved in the textural and chemical signature preserved in the compositional zoning of the titanites as dissolution and re-growth textures. This study illustrates that titanite is able to not only preserve evidence of magma mixing processes occurring at depth, but it is also able to preserve evidence of similar processes all the way through to the volcanic environment

In-situ Zircon and Monazite Geochronology from Compositionally Distinct Layers in a Single Migmatitic Paragneiss Sample Located in the Eastern Adirondack Mountains, NY

Migmatites are a common rock type in the Adirondack Mountains, NY. We analyzed a single sample of biotite-garnet-sillimanite paragneiss with foliation parallel leucosome along Route 22 south of Whitehall, NY in order to determine the timing of melting using both in-situ monazite and zircon U/Pb geochronology from the restite and leucosome layers of the same rock. Monazite was analyzed via in-situ EMPA on the Ultrachron microprobe at the University of Massachusetts. Zircon was analyzed via LA-ICP-MS (in-situ and mounted mineral separates) at the LaserChron Center. Monazite analyses from the restite yielded six compositionally distinct populations with dates of 1178 ± 16, 1139 ± 4, 1064 ± 6, 1049 ± 4, 1030 ± 5, and 1004 ± 10 Ma. Yttrium and heavy REEs decrease in monazite in two steps: one dramatic drop from ca. 1150 to 1065 Ma and another between ca. 1065 and 1050, interpreted to reflect two periods of garnet growth and melting. Analyses from the restite zircon separate yielded a significant single peak near 1050 Ma. These zircon grains exhibit fir-tree sector zoning texture which is interpreted to indicate crystallization from melt. Monazite from leucosome yielded a unimodal population at ca. 1050 Ma, however, backscatter images document alteration of monazite to apatite on the edges of the grains, and abundant uranothorite inclusions. Leucosome zircon analyses yielded a ca. 1150 Ma population from cores and a 1050 Ma population from rims. Cathodoluminescence imaging reveals that the zircon rims have textures indicative of fluid alteration. The data are consistent with these rocks undergoing two periods of melting. The first event at ca. 1150 Ma may have involved a non-garnet producing melting reaction, such as muscovite dehydration-melting. The second event at 1065 Ma involved significant garnet growth, interpreted to represent biotite dehydration-melting. Subsequently, the rocks underwent hydrothermal alteration at 1050 Ma. Monazite grains with dates at 1030 ± 5 and 1004 ± 10 Ma have higher yttrium concentrations suggesting garnet breakdown and monazite growth during decompression and retrograde metamorphism. A combination of monazite and zircon dating techniques from each compositional layer is necessary to constrain leucosome-restite relationships and to accurately interpret the timing of melting from migmatites that have experienced multiple phases of melting

Ordinal Trees and Random Forests: Score-Free Recursive Partitioning and Improved Ensembles

Existing ordinal trees and random forests typically use scores that are assigned to the ordered categories, which implies that a higher scale level is used. Versions of ordinal trees are proposed that take the scale level seriously and avoid the assignment of artificial scores. The basic construction principle is based on an investigation of the binary models that are implicitly used in parametric ordinal regression. These building blocks can be fitted by trees and combined in a similar way as in parametric models. The obtained trees use the ordinal scale level only. Since binary trees and random forests are constituent elements of the trees one can exploit the wide range of binary trees that have already been developed. A further topic is the potentially poor performance of random forests, which seems to have ignored in the literature. Ensembles that include parametric models are proposed to obtain prediction methods that tend to perform well in a wide range of settings. The performance of the methods is evaluated empirically by using several data sets

Magma fertility related to Au - Cu mineralisation: evaluating the potential for linked porphyry Cu - Au deposits at depths, North Queensland, Australia

Continental magmatic arcs host economically important porphyry ore deposit types for copper, gold, and molybdenum, and, if preserved, epithermal high- to intermediate-sulfidation gold and silver deposits. These deposits are genetically and/or spatially associated with magmatism, so understanding the link between magmatism and mineralisation is seen as a crucial endeavor to assist knowledge of mineralisation processes and strategies for regional-scale mineral exploration. This thesis examines aspects of the mineralisation potential of continental arc magmatic rocks that are exposed as part of the Permo-Carboniferous Kennedy Igneous Association (KIA) from northeastern Queensland. This belt of upper crustal intermediate to felsic granitoids and associated volcanic rocks is recognised to host many economic ore deposits related to igneous activity. Using well-established analytical techniques to analyze whole-rock and mineral major- and trace element compositions combined with Sm-Nd isotopes, I investigate two different localities related by their occurrence in time and space, with the aim to better understand magma fertility, or more specifically the petrogenetic processes contributing to Permo-Carboniferous Cu-Au mineralisation in northeast Queensland. This work strives to improve the applicability of magma fertility concepts to confidently identify fertile igneous terranes potentially covering high grade Cu-Au deposits at depth. The first location investigated lies to the south of Townsville at the northern edges of the Bowen Basin, where the early Permian Lizzie Creek Volcanic Group (LCV) hosts the Mount Carlton high-sulfidation epithermal Au-Cu deposit. Established whole-rock geochemical parameters, e.g. Sr/Y, V/Sc, used to distinguish fertile porphyry Cu-Au hosting intrusive rocks from barren intrusions, were tested on the "fertile" LCV succession, hosting the Mt. Carlton deposit and compared to contemporary "barren" volcanic rocks of the same group. The results reveal that the key control on generating the fertile LCV sequence was a high magmatic water content, reflected by early fractionation of amphibole at the source level, whereas the barren sequence was comparably dry, and formed by typical fractionation of plagioclase and clinopyroxene. This outcome has major implications for the applicability of whole rock geochemistry as a magma fertility indicator. The here presented results suggest that for volcanic rocks, which tend to be affected by hydrothermal alteration; a) Sr/Y is not a reliable fertility proxy and; b) Rare earth element ratios (e.g. La/Yb, Dy/Yb), which are relatively resistant to alteration, can be used to reveal differences in magmatic evolution. This supports previous research on magma fertility, and provides strong evidence that fertile magmatic suites can be identified from volcanics sequences that evolved from basalt to rhyolite with a progressive increase in La/Yb, decreasing Dy/Yb, and consistent or slightly increasing V/Sc ratios, despite having experienced some degree of alteration. The second location investigated in this thesis is the Tuckers Igneous Complex (TIC); a calc-alkaline, I-type igneous complex which intruded the Ravenswood Batholith between ~300-290 Ma and formed within the same convergent margin as the LCV. The TIC is part of the KIA and its relevance for this project lies within its close association with the major early Permian, breccia-hosted Mt. Leyshon Au deposit. The TIC contains a sequence of intrusive rocks from gabbro to felsic granodiorite, and hence offers the opportunity to investigate geochemical evolution, particularly volatile element evolution, of arc magmas at upper crustal levels. Here, I build on previous geochemical and petrographic data for the complex using newly acquired whole-rock geochemistry and in-situ mineral analyses of the major rock forming minerals plagioclase-clinopyroxene-orthopyroxene, and the halogen-bearing minerals apatite and biotite (and amphibole) to monitor and track volatile evolution (Cl and F). As volatile element behavior is recognised to have a fundamental control on magma fertility, this study, offers new insights into the fertility of this Permo-Carboniferous arc, which can be applied to other arc worldwide. My new results show that the TIC formed through closed-system crystal fractionation from gabbro to mafic granodiorite varieties with only minor mixing and/or assimilation, and likely became an open system during cooling and crystallisation of the more felsic granodiorites. Based on apatite halogen contents, volatile saturation is suggested to have occurred at around ~63-65 wt.% bulk-rock SiO₂, up to which point estimated Cl melt contents steadily rise, and then suddenly drop from ~0.8 to 0.4 wt.%. This abrupt change likely relates to the exsolution of a Cl-rich volatile phase, and also marks important changes within the mineral assemblage from a dry Plag ± Px ± Fe-Ti oxide assemblage, towards a more hydrous and slightly more oxidised Plag ± Hbl ± Bt ± Mag assemblage. Fluorine enriches in the melt with fractionation, even once saturation in a volatile phase is reached, consistent with what is expected from experimental partitioning studies in the system apatite – melt – fluid. Local or temporal changes in the magma's fO₂ is indicated by a measurable increase in apatite S contents in evolved felsic granodiorite, as apatite preferentially incorporates S as its oxidised species S⁶⁺, which also coincides with the general observed changes in the rock forming mineral assemblages as described above. Indicated volatile exsolution, causing loss of significant proportions of Cl together with oxidising conditions at which the bulk of dissolved S may have been present and possibly degassed as S⁴⁺O₂ (and causing the presence of low amounts of available S²⁻ to precipitate base metals) from the TIC magma may have caused mineralization within overlying, but now eroded rocks. A second possibility may be that the TIC was never able to produce mineralising fluids due to early segregation of sulfides, scavenging ore forming metals (e.g. Cu, Au, and Ag) prior to the crystallisation of TIC gabbro, and thereby stripping the TIC of its ore-forming potential early on. However, an exsolved Cl-rich fluid is very capable of transporting ore metals, therefore the role and true nature of such fluid(s) originating from the TIC can be subject of further investigations. The here presented results help to understand Cu-Au fertility on a regional, magmatic arc terrane (both volcanic and intrusive) from initial lower crustal petrological processes to the surface, but also on a local scale; within confined individual igneous bodies, their respective mineral assemblages, and their potential role towards regionally present Cu-Au mineralisation. In particular the findings on volcanic rocks offer great potential as easily accessible first-order fertility assessment tool for magmatic-hydrothermal Cu-Au exploration worldwide