Geophysical characteristics of the southern Coromandel Volcanic Zone, New Zealand, and associated epithermal deposits

Locke, Corinne A.; Cassidy, John F.; Harris, Matthew C.; Kirkby, Alison; Mauk, Jeffrey L.; Morrell, Anne E.; Rowland, J. V.; Smith, N.

doi:10.1071/aseg2007ab076

Cited by 2 publications

(2 citation statements)

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“…Similar positive anomalies have subsequently been identified at other deposits in the southern Coromandel (Harris et al, 2005;Kirkby, 2008), which suggests that these enigmatic dense structures are not unique to Waihi, though, as noted previously, similar gravity anomalies have not been identified outside New Zealand. It may be significant that all these deposits are located adjacent to the major regional faults delineating the Waihi basin structure (Locke et al, 2007). To date, no positive anomalies have been resolved in the Waitekauri Valley, and the Golden Cross and Scotia deposits are associated with local negative anomalies (Locke and de Ronde, 1987).…”

Section: Discussionmentioning

confidence: 98%

“…To date, no positive anomalies have been resolved in the Waitekauri Valley, and the Golden Cross and Scotia deposits are associated with local negative anomalies (Locke and de Ronde, 1987). There is some indication, however, of a positive anomaly toward the north of the Waitekauri Valley (Maratoto; de Ronde, 1985;Locke et al, 2007), but this is poorly defined due to a paucity of data.…”

Section: Discussionmentioning

confidence: 99%

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Geophysical Characteristics of Adularia-Sericite Epithermal Gold-Silver Deposits in the Waihi-Waitekauri Region, New Zealand

et al. 2011

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Aeromagnetic, airborne radiometric, and surface gravity data from the adularia-sericite epithermal province of the Hauraki goldfield have delineated distinct anomalies associated with pervasive hydrothermal alteration and gold-silver mineralization. Aeromagnetic derivative images, particularly the analytic signal, define the boundaries of several magnetic quiet zones that result from magnetite destruction in the volcanic host rocks. Six discrete zones, each of ≤10-km 2 areal extent are evident and are comparable in size to modern-day geothermal systems in the Taupo volcanic zone. An extensive (>20-km 2) zone in the Waitekauri Valley is likely to be the result of multiple overlapping systems, for which there are also analogues in the Taupo volcanic zone that form single large-scale alteration zones up to 100 km 2. Low-pass filtering of the analytic signal data reveals still wider zones of relatively low magnetic intensity interpreted as areas of hydrothermally altered rock extending below younger, unaltered cover. Many of these magnetic quiet zones are aligned along a north-northeast-south-southwest structural corridor, indicating that regional-scale structures may have controlled the location of these geophysical features. Radiometric data delineate local high potassium anomalies that reflect up to 12/100 g potassium enrichment in the core of alteration zones in the form of adularia and illite. A broad K/Th anomaly correlates with the extent of the magnetic quiet zones and indicates widespread potassium enrichment in the Waitekauri-Maratoto area. Gravity data in the Waihi district define a unique, double-peaked, 50-gravity unit positive residual anomaly that correlates closely with the extent of the magnetic quiet zone and the locations of the Waihi and Favona deposits. Preliminary modeling indicates that the anomaly source body, beneath the near-surface, low-density altered andesite, has a volume of up to ~11 km 3 and a minimum density of 2,900 kg m-3. The nature of this source body is enigmatic; possible causes include a dense intrusion, uplifted anomalously dense basement, dense sulfide mineralization, or some combination of these. In addition, the correlation of each of the two gravity peaks with a north-northeast-trending fault may indicate some structural focusing process active at the deposit scale. This integration of geophysical data provides an outstanding case study of the district-to regional-scale geophysical characteristics of a classic epithermal province and demonstrates the strengths of geophysical surveys in the exploration for epithermal mineral deposits.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Geophysical Characteristics of Adularia-Sericite Epithermal Gold-Silver Deposits in the Waihi-Waitekauri Region, New Zealand

et al. 2011

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Geophysical prospecting for epithermal gold deposits (a case study from the Maletoivayam gold ore field, Kamchatka Peninsula)

Gurin¹

2021

Lithosphere

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Research subject. The high-sulfidation (HS-type) epithermal gold deposits of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula. Materials and methods. The paper presents the results of geophysical and petrophysical studies carried out by “NPP VIRG-Rudgeofizika” (2016–2017 years) in the central part of the Maletoyvayam ore field hosting HS-type gold deposits. Results. The presented case study shows the potential of geophysical prospecting for HS-type epithermal gold deposits located within altered rock areas. On the basis of the conducted magnetic surveys, fragments of a ring structure broken by faults and the hydrothermally altered bodies within the Neogene volcanogenic-sedimentary sequence of the andesite composition were identified. Using the 3D inversion of magnetic data, the shape, size and structure of the hydrothermally altered bodies were estimated. The electrical survey data allowed the hydrothermally altered areas to be differentiated in terms of composition. As a result, zoning of hydrothermally altered areas was conducted, and ore-bearing sites and gold-bearing bodies of monoquartzites in the plan and cross-section were determined. Conclusions. Geophysical techniques for prospecting HS-type epithermal gold deposits are effective in distinguishing important gold-related features within the altered zone thereby facilitating identification of specific drill targets.

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Geophysical characteristics of the southern Coromandel Volcanic Zone, New Zealand, and associated epithermal deposits

Cited by 2 publications

References 12 publications

Geophysical Characteristics of Adularia-Sericite Epithermal Gold-Silver Deposits in the Waihi-Waitekauri Region, New Zealand

Geophysical Characteristics of Adularia-Sericite Epithermal Gold-Silver Deposits in the Waihi-Waitekauri Region, New Zealand

Geophysical prospecting for epithermal gold deposits (a case study from the Maletoivayam gold ore field, Kamchatka Peninsula)

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