Item talk:Q300139

{

 "USGS Publications Warehouse": {
   "@context": "https://schema.org",
   "@type": "CreativeWork",
   "additionalType": "Book Chapter",
   "name": "Exploration and geology of the Karangahake and Rahu epithermal Au-Ag deposits, Hauraki Goldfield",
   "identifier": [
     {
       "@type": "PropertyValue",
       "propertyID": "USGS Publications Warehouse IndexID",
       "value": "70178775",
       "url": "https://pubs.usgs.gov/publication/70178775"
     },
     {
       "@type": "PropertyValue",
       "propertyID": "USGS Publications Warehouse Internal ID",
       "value": 70178775
     }
   ],
   "inLanguage": "en",
   "datePublished": "2016",
   "dateModified": "2017-03-16",
   "abstract": "Karangahake was the third largest gold producer in the Hauraki goldfield. In 2009, New Talisman Gold mines was granted a mining permit, and plans are underway to commence underground mine development of the Maria vein, which has a maiden Ore Reserve (consistent with the 2012 JORC Code) of 28 800 oz Au and 127 800 oz Ag. Exploration drilling at Rahu, located 2 km north of Karangahake has identified polymictic hydrothermal breccias and quartz veins that are strongly gold anomalous. Some quartz vein clasts within the breccia have up to 8.7 g/t Au, suggesting the presence of higher grade quartz vein(s) either below or directly adjacent to the breccias. A controlled source audio-frequency magnetotelluric (CSAMT) survey at Rahu revealed that strongly resistive zones extend below the Barbara and Eunice anomalies to at least 300 m depth and likely correspond to areas of increased silicification, breccias and/or veins. Future drilling will focus on these targets. \nDetailed geophysical, alteration and fluid inclusion studies have been undertaken at Karangahake, Rahu and Ascot (c 1 km NW of Rahu). Karangahake and Rahu both occur within a broad demagnetised zone, c 4.2 \u00d7 2.7 km, in which magnetite has been destroyed by strong hydrothermal alteration. At Karangahake, andesite and overlying minor rhyolite are replaced by adularia, chlorite, illite, pyrite, plus minor albite, epidote and calcite, which have formed from upwelling chloride waters that at depth were hotter than 280\u00b0C. At Rahu, localised adularia coupled with complex distributions of illite and interstratified illite-smectite, suggest cooler (c 180\u00b0 to 240\u00b0C) and more focused fluid flow, as well as inferred cool groundwater influx. Fluid inclusion data suggest veins at Karangahake, Rahu and Ascot formed beneath palaeowater tables at 920 m, 440 m and 430 m relative to current sea level (asl), respectively. At Ascot, the presence of silica sinter at 135 m asl, which formed at the palaeosurface, is shallower compared to the fluid inclusion depth estimate and suggests that the palaeowater table here rose some 300 m during hydrothermal activity due to burial, resulting in overprinting. This overprint may also have occurred at Karangahake and Rahu, but the evidence is inconclusive; although burial during hydrothermal activity could explain the exceptional 700 m vertical range of mineralisation at Karangahake and raises the possibility of concealed mineralisation at depth elsewhere within the Karangahake alteration envelope.",
   "description": "10 p.",
   "publisher": {
     "@type": "Organization",
     "name": "The Australasian Institute of Mining and Metallurgy"
   },
   "author": [
     {
       "@type": "Person",
       "name": "Mauk, Jeffrey L. jmauk@usgs.gov",
       "givenName": "Jeffrey L.",
       "familyName": "Mauk",
       "email": "jmauk@usgs.gov",
       "identifier": {
         "@type": "PropertyValue",
         "propertyID": "ORCID",
         "value": "0000-0002-6244-2774",
         "url": "https://orcid.org/0000-0002-6244-2774"
       },
       "affiliation": [
         {
           "@type": "Organization",
           "name": "Central Mineral and Environmental Resources Science Center",
           "url": "https://www.usgs.gov/centers/gggsc"
         }
       ]
     },
     {
       "@type": "Person",
       "name": "Simpson, Mark P.",
       "givenName": "Mark P.",
       "familyName": "Simpson",
       "affiliation": [
         {
           "@type": "Organization",
           "name": "The University of Auckland"
         }
       ]
     },
     {
       "@type": "Person",
       "name": "Stevens, Murray R",
       "givenName": "Murray R",
       "familyName": "Stevens"
     },
     {
       "@type": "Person",
       "name": "Harris, Matthew C",
       "givenName": "Matthew C",
       "familyName": "Harris"
     },
     {
       "@type": "Person",
       "name": "Stuart, Alistair G J",
       "givenName": "Alistair G J",
       "familyName": "Stuart"
     }
   ],
   "funder": [
     {
       "@type": "Organization",
       "name": "Central Mineral and Environmental Resources Science Center",
       "url": "https://www.usgs.gov/centers/gggsc"
     }
   ]
 }

}