Related by context. All words. (Click for frequent words.) 69 Induced polarization 69 Detailed geological mapping 68 dipole dipole IP 68 IP induced polarization 68 infill sampling 67 lithogeochemical 67 induced polarization 67 outcrop sampling 67 Geochemical sampling 67 Induced Polarisation 67 ground magnetics 67 soil geochemical survey 67 IP Resistivity 66 magnetic electromagnetic 66 soil geochemical 66 pole dipole 66 magnetite alteration 66 anomalies coincident 66 magnetometric 66 UTEM 66 coincident geochemical 66 Induced Polarization 65 IP geophysical surveys 65 surface geochemistry 65 IP chargeability 65 coincident magnetic 65 induced polarization geophysics 65 coincident geophysical 65 airborne EM 65 EM geophysical 65 borehole geophysics 65 Megatem 65 Geophysical surveys 65 soil geochemical surveys 65 airborne radiometric anomalies 65 3D induced polarization 65 geochemical soil 65 transient electromagnetic 65 stream sediment geochemical 64 Soil geochemical 64 MMI soil geochemical 64 IP resistivity 64 magnetometer survey 64 mapping trenching 64 Ni Cu PGM mineralization 64 disseminated sulphide mineralization 64 Gradient Array 64 detailed geologic mapping 64 termite mound sampling 64 geophysical conductors 64 3D Induced Polarization 64 CSAMT 64 anomalous soil geochemical 64 resistivity anomalies 64 induced polarization anomalies 64 Ground geophysics 64 coincident chargeability 64 airborne geophysical surveying 64 gold geochemical anomalies 64 outcropping mineralization 64 IP geophysical surveying 63 geophysical geochemical 63 MMI anomalies 63 penetrating electromagnetic 63 gradient array 63 Soil geochemistry 63 MMI geochemistry 63 induced polarization surveys 63 silica pyrite 63 magnetometer surveys 63 IP geophysics 63 anomalous geochemical 63 mapping prospecting 63 geological mapping trenching 63 Detailed mapping 63 geophysics trenching 63 #m@#.#g t Au [001] 63 dravite 63 coincident gravity 63 Shirotnaia zone 63 Induced Polarisation IP 63 Geological mapping 63 Cobrecon 63 downhole geophysics 63 strongly silicified 63 electro magnetic EM 63 geologically mapped 63 InfiniTEM survey 63 Kasala Main Zone 63 Titan# 63 anomalous chargeability 63 ground geophysical surveying 63 radiometric surveys 63 VTEM surveys 63 magnetic geophysical surveys 63 magnetic geophysical 63 geochem anomalies 63 geochemical geophysical 63 IP geophysical 63 electromagnetic surveys 63 induced polarization IP 63 EM geophysical survey 63 geochemical surveying 63 gravity geophysical surveys 63 VTEM geophysical 63 sampling geological mapping 63 borehole geophysical 63 CSAMT geophysical survey 63 mineralization encountered 63 #WR# 63 alaskite 63 sulphide mineralization intersected 63 IP chargeability anomaly 63 ZTEM 63 radiometrics 63 Geophysical Survey 63 Nyota Prospect 62 IP resistivity survey 62 manganese mineralization 62 Anomalous uranium 62 dacitic 62 composited assay 62 XDS VLF EM 62 surface trenching 62 HLEM 62 Aricheng West 62 Induced Potential 62 resistivity surveys 62 structural lineaments 62 airborne magnetic radiometric 62 induced polarization IP chargeability 62 gold anomalism 62 Bellechasse Timmins deposit 62 Resistivity 62 #m@#.#g t [006] 62 geophysical surveying 62 airborne magnetic anomalies 62 geochem 62 mineralized skarn 62 MegaTEM 62 inversion modeling 62 litho geochemical 62 airborne radiometric magnetic 62 IP geophysical anomalies 62 conductive zones 62 NSAMT 62 quartz sericite pyrite alteration 62 induced polarization geophysical surveys 62 geological reconnaissance 62 surficial 62 intersected mineralized 62 stringer mineralization 62 REE bearing 62 radiometric survey 62 penetrating geophysical 62 airborne geophysical anomalies 62 vanadium mineralization 62 anomalous radiometric 62 geochemical assay 62 airborne radiometric 62 calcrete sampling 62 Mobile Metal Ions 62 OTD# 62 silicic 62 Bejucosa 62 induced polarization survey 62 Etango deposit 62 surface outcrops 62 Induced Polarization IP chargeability 62 radiometric airborne 62 soil geochemistry 62 soil geochemical anomalies 62 InfiniTEM 62 Chalcopyrite 62 linecutting 62 aircore drill 62 airborne VTEM 62 Ground geophysical surveys 62 Soil sampling 62 Las Boquillas 62 Au Cu mineralization 62 dipole dipole 62 Kay Tanda 62 prospecting trenching 62 soil geochemical sampling 62 induced polarization geophysical 62 mineralized intrusive 62 Sian Praso 62 stockwork vein 62 Time Domain Electromagnetic 62 gossans 62 airborne magnetics 62 geophysical surveys 62 IP Resistivity surveys 62 Oshiveli 62 Klaza Zone 62 Takom 61 Hambok 61 #m@#.#g t gold [002] 61 uranium mineralization intersected 61 BHEM 61 airborne electromagnetic EM 61 DEEPEM 61 Kaukua 61 adit sampling 61 detailed airborne magnetic 61 lake sediment geochemical 61 km induced polarization 61 VTEM targets 61 Tres Juanes Norte 61 Extension Occurrence 61 albitite 61 mineralized zones intersected 61 ground magnetometer surveys 61 intersected anomalous 61 anomaly coincident 61 vein stockwork 61 anomalism 61 Mt Penck 61 mineralized breccia 61 northerly trending 61 Komahun 61 petrographic studies 61 diorite porphyry 61 mechanical trenching 61 sericitic 61 reconnaissance mapping 61 Onkelo 61 ground radiometric surveys 61 copper anomalism 61 intersect mineralization 61 Gongondy 61 Quantec Titan 61 Alaskite 61 #.#g t Ag [005] 61 mapping geochemical sampling 61 Taricori 61 Tagpura 61 pyritized 61 Black Thor chromite 61 outcrop exposures 61 resistivity geophysical 61 auriferous zones 61 mineralized outcrops 61 Junnagunna 61 geology geochemistry 61 helicopter borne VTEM 61 airborne magnetic anomaly 61 #m@#.#g t gold [001] 61 veins stockworks 61 trenching sampling 61 alteration assemblages 61 aeromagnetics 61 quartz hematite 61 IP Resistivity survey 61 coincident anomalous 61 airborne magnetic 61 ground radiometric surveying 61 sulphide mineralized 61 surface geochemical anomalies 61 airborne magnetometer 61 TDEM survey 61 skarn alteration 61 IP chargeability anomalies 61 geochemical 61 VTEM conductor 61 arsenic anomalies 61 mineralogical studies 61 Luhwaika 61 exhalite 61 Golouma West 61 anomalous soil geochemistry 61 geological mapping geochemical 60 Korkan target 60 magnetic geophysical anomaly 60 Goldpines North 60 carbonate veins 60 approximately #km# [002] 60 Ntaka Hill 60 prospecting mapping 60 geophysical interpretation 60 +# ppb 60 electromagnetic geophysical 60 chargeability IP 60 MEGATEM 60 VTEM airborne 60 Airborne geophysics 60 advanced argillic 60 El Compas 60 aircore drilling 60 Drill intersections 60 gravity anomalies 60 basal till 60 electromagnetic surveying 60 gold copper porphyry 60 averaging #.#g t [003] 60 Enzyme Leach soil 60 felsic intrusive rocks 60 disseminated magnetite 60 intensely silicified 60 quartz stockworks 60 intersected silicified 60 prospecting geological mapping 60 scintillometer surveys 60 #ppb gold 60 coincident IP chargeability 60 Felsic 60 Drill Hole Locations 60 Sicera Sur 60 intense silicification 60 Au Ag mineralization 60 hematite mineralization 60 detailed aeromagnetic survey 60 Mouchalagane 60 PGM mineralization 60 JAK Zone 60 Koshaj 60 extensive artisanal workings 60 hydrothermal brecciation 60 Magusi deposit 60 geologic mapping 60 ankerite 60 electromagnetic geophysical survey 60 palaeochannel 60 Lamothe Showing 60 potassically altered 60 mineralized alteration 60 mineralized drill intercepts 60 hydrothermally altered 60 disseminated sulphide 60 Au Cu Ag 60 Anuri kimberlite 60 iron carbonate alteration 60 Manzako Prospect 60 spodumene pegmatite 60 chargeability anomalies 60 Radiometric 60 Azulitas 60 sheeted veins 60 VTEM anomalies 60 Siribaya mega structure 60 Tortigny deposit 60 Electromagnetic EM 60 anomalous geochemistry 60 Animas vein 60 chalcocite covellite 60 downhole geophysical 60 molybdenite mineralization 60 rockchip 60 porphyry intrusives 60 geophysical modeling 60 stockworked 60 Kavola East 60 multielement 60 altered felsic 60 mafic intrusives 60 geological mapping sampling 60 Timmins Porcupine West 60 Archean aged 60 geophysics prospecting 60 potentially open pittable 60 Lone Pine Property 60 Colnic 60 stockwork veining 60 Lithology 60 airborne geophysical surveys 60 Zone Bambadinka 60 Hugla Tepe 60 phyllic 60 Aurizona Main 60 anomalous molybdenum values 60 drilled thicknesses 60 Dachang Main Zone 60 Induced Polarization IP 60 mineralized quartz 60 Matala deposit 60 borehole EM 60 Cerro Vetas 60 WDC# 60 magnetic susceptibility 60 Ni Cu PGE mineralization 60 gamma ray spectrometry 60 pegmatite veins 60 intersected sulphide 60 Rare Earth Element REE 60 Itilima 60 Rojo Grande 60 intersected kimberlite 60 mineralized shear zone 60 wallrocks 60 advanced argillic alteration 59 IP geophysical anomaly 59 m@#.# g t Au [002] 59 #RB# 59 copper mineralization intersected 59 Calandria Sur 59 granodiorite porphyry 59 alunite alteration 59 Magnetic susceptibility 59 Bedard Dyke 59 molybdenum porphyry 59 Airborne Geophysical 59 aircore 59 Horizontal Loop Electromagnetic 59 Quebrada Verde 59 alteration halo 59 silica breccia 59 auger drill 59 VTEM conductors 59 geochemically anomalous 59 subhorizontal 59 sampling trenching 59 variably mineralized 59 mylonite 59 #ppb Au [002] 59 airborne electromagnetic 59 VTEM airborne survey 59 mineable widths 59 -Wauk 59 Leprechaun Pond 59 excavator trenching 59 aeromagnetic anomalies 59 Pokukrom East 59 altered granodiorite 59 Roughrider East 59 Dioulafoundou 59 VTEM airborne geophysical 59 Geotech VTEM 59 Itigi Manyoni Uranium 59 poly metallic mineralization 59 Huarabagoo 59 Simuku 59 Norlartic 59 geophysical induced polarization 59 geophysical surveys trenching 59 biotite rich 59 Klappibacken 59 NQ diamond 59 Calandria Norte 59 surface geochemical sampling 59 copper molybdenum mineralization 59 epithermal alteration 59 airborne radiometrics 59 spaced drill 59 South Barnat 59 induced polarization resistivity 59 Cerro Amarillo 59 Calvario Vein 59 anomalous zinc 59 Kierens 59 #km 2D seismic 59 petrological 59 VTEM airborne surveys 59 Big Daddy Chromite 59 uraniferous 59 Cambrian Ordovician 59 coincident magnetic anomaly 59 Aeromagnetic 59 Cuiu Cuiu 59 Dubenski Shaft Zone 59 reconnaissance geological mapping 59 Reverse Circulation drilling 59 South Minita 59 EW trending 59 auriferous 59 conductive anomaly 59 mineralized gabbro 59 Roughrider uranium deposit 59 #m@#.# g t [004] 59 anomalous zones 59 BHEM surveys 59 mineralized envelope 59 pyrophyllite 59 saprolitic 59 Alaskite Zone 59 lake sediment geochemistry 59 radiometric readings 59 Malartic Lakeshore property 59 antimony Sb 59 Nemegosenda 59 geological mapping prospecting 59 kimberlite breccia 59 phyllic altered 59 Carbonatite Complex 59 magnetite BIF 59 Induced polarization IP 59 Teapot Granite 59 Ciresata 59 VTEM 59 altered rhyolite 59 Bambadinka trend 59 Cu Au mineralization 59 Quantec Geoscience 59 Handeni Gold Trend 59 sheeted quartz 59 Highbank Lake 59 mineralized quartz veins 59 vein stockworks 59 vein breccia 59 metavolcanic 59 Harena 59 potassic alteration 59 calc silicate 59 mineralized felsic 59 sulphide bearing 59 holes #WR# 59 Yaxtche deposit 59 Tatajuba 59 Los Candelones 59 carbonatite complex 59 borehole electromagnetic 59 BB# [002] 59 shallowly dipping 59 sylvinite 59 rhyolite domes 59 Fayolle Property 59 drillhole spacing 59 potentially bulk mineable 59 bulldozer trenching 59 Marge Vein 59 MEGATEM II 59 intrusive breccias 59 ENE trending 59 airborne radiometric survey 59 radiometric anomaly 59 outcropping vein 59 mineralized outcrop 59 Mineral Resource estimation 59 quartz sericite pyrite 59 kilometer airborne magnetic 59 Kirana Break 59 Airborne Magnetic 59 subcrop 59 Clementine vein 59 TDEM 59 talc chlorite 59 Norpax Deposit 59 Hibou dyke 59 aeromagnetic 59 geophysical conductor 58 sub Athabasca unconformity 58 Enzyme Leach 58 ground geophysical surveys 58 conductive anomalies 58 airborne radiometric anomaly 58 epithermal gold targets 58 silicified breccia 58 electromagnetic conductors 58 lithocap 58 conductivity anomalies 58 Zam Zam Shenkman 58 stockwork veined 58 Rusk Zone 58 brecciated quartz 58 dyke swarms 58 ZTEM survey 58 quartz molybdenite 58 geochemical surveys 58 prospective stratigraphy 58 previously unsampled 58 Footwall Zone 58 magnetic anomalies 58 silicic alteration 58 niobium mineralization 58 mapping geochemistry 58 jasperoids 58 mineralized hydrothermal 58 REE mineralized 58 magnetite mineralization 58 calcrete 58 mafic intrusions 58 Marban deposit 58 hydrothermal alteration 58 Induced Polarization Resistivity 58 Toro Gregorio 58 aero magnetic 58 #m@#.#g t Au [003] 58 Epithermal 58 albitized 58 Segala Main 58 Kena Property 58 #m@#.#g t Au [005] 58 stream sediment 58 geochemical sampling 58 element geochemistry 58 soil geochemical anomaly 58 downhole EM 58 Arsenopyrite 58 gossan 58 epithermal gold vein 58 Airborne EM 58 detailed geological mapping 58 HRAM 58 reconnaissance prospecting 58 trending shear zone 58 overburden sampling 58 quartz sulphide vein 58 radiometric anomalies 58 sulfide bearing 58 electromagnetic EM geophysical 58 gravity anomaly 58 Somituri Project 58 Induced Polarization surveys 58 chromitite layers 58 underground delineation drilling 58 Fofina 58 magnetometry 58 talus fines 58 hematitic 58 drillhole database 58 Cu Au 58 mechanized trenching 58 Geophysical surveying 58 airborne geophysics 58 mineralized pegmatite 58 Suuri zone 58 andesitic 58 magnetometric survey 58 resolution airborne magnetic 58 meter spacing 58 silica alteration 58 Atikwa Lake property 58 Encino Vein 58 magnetic radiometric 58 antimony mineralization 58 excavator trenches 58 unoxidized 58 silicified zone 58 mineralized dykes 58 Tantamaco 58 delineation drill 58 radiometric magnetic 58 gamma logging 58 Dioulafoundou zone 58 airborne electro magnetic 58 abundant pyrite 58 pathfinder element 58 resistivity anomaly 58 Pokukrom West 58 Savkino 58 Juanicipio Vein 58 massive sulphide horizon 58 enzyme leach 58 vuggy silica quartz alunite 58 Dienemera 58 Guajes West 58 coal seam thickness 58 downhole lengths 58 Lower Acacus Formation 58 ODAE 58 Brucejack Area 58 chromite mineralization 58 polymetallic mineralization 58 Tiriganiaq 58 Igunda 58 aeromagnetic survey 58 mineralized breccias 58 Ida Dome 58 #.#g t Ag [004] 58 Nemegosenda Project 58 corehole 58 Adumbi Prospect 58 Ciresata deposit 58 chromitite 58 Cu Zn Ag 58 AHGZ 58 alteration mineralization 58 Norra Karr 58 tuffaceous sediments 58 variography 58 Yarumalito 58 borehole Pulse 58 airborne radiometric surveys 58 vein outcrops 58 auger sampling 58 pathfinder elements 58 alaskite hosted 58 anomalous radioactivity 58 Matoush fault 58 stratigraphically below 58 Cerro Moly 58 radiometric prospecting 58 Haquira East 58 Emba Derho deposit 58 Puella Bay 58 EM conductor 58 anomalous Au 58 aircore drill holes 58 Zamora Batholith 58 eluvial 58 Tassawini 58 scintillometer survey 58 Kitenge Prospect 58 gossanous 58 polymetallic vein 58 Adi Nefas 58 dike swarm 58 altered diorite 58 Sulphides 58 bulk minable gold 58 hole RC# 58 lithologic 58 steeply dipping fault 58 Geologic mapping 58 pediment gravels 58 extensional drilling 58 diorites 58 uranium vanadium mineralization 58 stockwork mineralization 58 variogram 58 silicified breccias 58 geochemical anomaly 58 ultramafic intrusives 58 geophysical interpretations 58 REE enriched 58 Shirotnaia 58 ANIT 58 grade mineralization intersected 58 Aappaluttoq 58 trending mineralized 58 Las Bolas structure 58 metres@#.#g t gold 58 #m@#.#g t Au [004] 58 Djambaye 58 Soil Anomaly 58 nickel laterite mineralization 58 intrusive breccia 58 Kaniago 58 epithermal quartz veins 58 auger drilling 58 airborne electromagnetic anomalies 58 Dubenski property 57 Renard cluster 57 Gravity Survey 57 meter spacings 57 chrome diopside 57 uranium anomalism 57 inferred resource calculation 57 Guayabales 57 layered mafic 57 Tiriganiaq deposit 57 EM anomalies 57 Cumpie Hill 57 Geophysical Surveys 57 mineralized diorite 57 geological geochemical 57 Airborne Survey 57 stockwork breccia 57 Cordero Porphyry 57 EM conductors 57 Intersected 57 airborne geophysical 57 Miwah Gold Zone 57 lateral extensions 57 sericite carbonate 57 Induced Polarization anomaly 57 El Cometa 57 airborne EM survey 57 Sesmo Sur 57 Cu Au Mo 57 deformation corridor 57 CSAMT survey 57 geochemical anomalies 57 #:#,# scale [002] 57 magnetite ilmenite mineralization 57 andesitic volcanics 57 Amun Deeps 57 Carbonatite 57 Higo Blanco 57 Lupoto 57 silicification quartz 57 intersected disseminated 57 #m@#.# g t [002] 57 Takom Zone 57 Reverse Circulation 57 drillhole intersected 57 NE trending 57 Zn Ag 57 Cu Mo Au 57 Ni Cu PGM 57 Dombraly 57 airborne anomalies 57 Ccaccapaqui 57 gold porphyry mineralization 57 Quebrada Pedregosa 57 hydrothermal breccias 57 Landsat imagery 57 volcanogenic massive sulfide 57 trench sampling 57 leached capping 57 #m@#.# g t Au [004] 57 Akasaba Mine 57 DUB# 57 radiometric surveying 57 altered andesitic 57 Uranium mineralization 57 arsenopyrite veins 57 abundant quartz veining 57 extrusive 57 Volcanogenic Massive Sulphide VMS 57 conglomeratic 57 Shaft Zone 57 vuggy silica alteration 57 heliborne magnetic 57 massive chromite 57 Quantec Geoscience Limited 57 geochemistry anomalies 57 geological interpretations 57 AeroTEM III 57 soil geochemistry surveys 57 Minita deposit 57 penetrating induced polarization 57 alluvial workings 57 Ni Cu Co 57 radon anomalies 57 ZrO2 57 electromagnetic anomalies 57 layered ultramafic 57 shallow laterally 57 anomalous REE 57 resistivity surveying 57 electromagnetic EM survey 57 Haukiaho 57 Ayelen vein 57 anomalous concentrations 57 pelitic gneiss 57 PdA Extension 57 pyrite altered 57 IOCG mineralization 57 Preliminary metallurgical testwork 57 colluvial 57 sheeted quartz veinlets 57 geological mapping geochemical sampling 57 drill hole NAD# 57 EM geophysical surveys 57 McFauld 57 Banded Iron Formation 57 mineralogical analysis 57 geochemical samples 57 Larder Lake Property 57 Bulk sampling 57 intersected anomalous radioactivity 57 Barkerville Mountain 57 chloritic 57 Cretaceous sandstones 57 intersected anomalous gold 57 argillic alteration 57 Yaxtché deposit 57 sulphide lenses 57 Accha deposit 57 chargeability anomaly 57 Au Cu 57 Nithi Mountain 57 intersected sulphide mineralization 57 IOCG targets 57 Silica Ridge 57 arsenopyrite bearing 57 Hushamu 57 locally graphitic 57 geochemical assays 57 geophysical geological 57 Nyafe 57 stream sediment geochemistry 57 drillhole intersections 57 Memouniat Formation 57 vuggy silica 57 spodumene bearing 57 Darnley Bay gravity 57 NAD# [002] 57 Nfante East 57 AeroTEM II 57 soil sampling trenching 57 Fayolle Project 57 ODM# Zone 57 Wona SW Zone 57 sheeted vein 57 volcaniclastic rocks 57 hypabyssal kimberlite 57 volcanic stratigraphy 57 flotation testwork 57 disseminated stringer 57 stepout drilling 57 oxidized mineralization 57 Geodatos 57 La Lechoza Prospect 57 Zn Pb 57 coincident induced polarization 57 gold arsenic antimony 57 Artavasdes 57 sulphidized 57 Dogpaw 57 trenching mapping 57 argillic 57 massive sulfide mineralization 57 Cobre Grande 57 mineralized horizons 57 northwesterly trending 57 lithological units 57 licenses PL# 57 REE mineralization 57 Naciente Quebrada Pedregosa 57 ground geophysics 57 Tuqueque 1X 57 diamond drillholes 57 regolith mapping 57 Sudbury Breccia 57 anomalous uranium 57 supergene zone 57 holes RR# 57 Abel Knoll 57 molybdenite bearing 57 Significant intercepts 57 Induced Polarization geophysical surveys 57 propylitic 57 magnetite skarn 57 bearing hydrothermal 57 #WA 57 IP Induced Polarization 57 granitoids 57 hornfels 57 MMI geochemical 57 Frankfield East 57 intersected variably 57 quartz muscovite 57 Malundwe 57 chalcopyrite sphalerite 57 greenstones 57 IOCGU 57 NNW trending 57 epithermal veins 57 mafic intrusive 57 mafic intrusion 57 epidote 57 Dogpaw No. 57 geochemical analyzes 57 magnetic geophysical anomalies 57 rhyolite tuffs 57 hydrothermal breccia 57 Fugro Ground 57 Uranium Mineralization 57 Lac Pivert Rose 57 Mothae pipe 56 sulphide occurrences 56 magnetite bearing 56 gabbro dykes 56 lamprophyre 56 Pasfield Lake 56 Szolnok Formation 56 Sulphurets deposit 56 gabbro dyke 56 MEGATEM survey 56 High Resolution Aeromagnetic 56 dunite 56 Penasco Quemado 56 Anchaca 56 Represa Zone 56 Thor Trend 56 Djambaye II 56 Anomalous gold 56 West Pequop 56 breccia zones 56 Fossey Zone 56 geophysical 56 Massive Sulfide 56 porphyry breccia 56 magnetite hematite 56 Pinguino property 56 geophysical survey 56 anomalous mineralization 56 Basal Zone mineralization 56 Pulse EM 56 hematite altered 56 epithermal vein 56 Pivert East 56 Limosna 56 Aricheng C 56 grade interpolation 56 Mag EM 56 Hache lens 56 Golouma South 56 Cu PGE 56 metavolcanic rocks 56 epithermal quartz 56 Ouro Verde deposit 56 VTEM anomaly 56 argillic altered 56 cobalt mineralization 56 Wasamac property 56 resource delineation drilling 56 Pidgeon Molybdenum Deposit 56 geostatistical analysis 56 quartz veined 56 Eastford Lake 56 supergene copper 56 tungsten mineralization 56 gold mineralized quartz 56 arsenic antimony mercury 56 geological mapping geochemistry 56 alteration zones