Chapter 26: Geology of the Hishikari Gold Deposit, Kagoshima, Japan

2020 ◽  
pp. 545-558
Author(s):  
Takayuki Seto ◽  
Yu Yamato ◽  
Ryota Sekine ◽  
Eiji Izawa
Keyword(s):  
Fluid Flow ◽  
Gold Deposit ◽  
Sedimentary Rocks ◽  
Alteration Zone ◽  
Volcanic Area ◽  
Mineral Zone ◽  
Temperature Controlled ◽  
Hydrothermal Alteration Zones ◽  
Low Sulfidation ◽  
Ore Grade

Abstract The bonanza-grade, low-sulfidation epithermal Hishikari gold deposit is located in the Plio-Pleistocene volcanic area of southern Kyushu, Japan. The concealed veins were discovered in 1981 and the mine has since produced 5.462 million metric tons (Mt) of ore averaging 44.3 g/t Au (242 t Au) from 1985 to the end of 2018, at which time reserves were 7.98 Mt at 20.9 g/t Au. The Hishikari deposit consists of the Honko, Sanjin, and Yamada ore zones, which occur in a NE-trending area 2.8 km long and 1.0 km wide. The veins are hosted by basement sedimentary rocks of the Cretaceous Shimanto Supergroup and by overlying Hishikari Lower Andesites of Pleistocene age. Sinter occurs about 100 m above the Yamada ore zone. Temperature-controlled hydrothermal alteration zones occupy an area of >5 km long and 2 km wide. The Honko and Sanjin veins occur within a chlorite-illite alteration zone (paleotemperature >230°C), whereas the Yamada veins occur within an interstratified clay mineral zone (150°–230°C). The marginal alteration comprises quartz-smectite (100°–150°C) and cristobalite-smectite (<100°C) zones. Ore-grade veins are located between –60- and 120-m elev, with the paleowater table over the Honko-Sanjim veins at ~300-m elev. Overall, the Ag/Au wt ratio is about 0.6. Vein-forming minerals consist of quartz, adularia, and clay minerals plus truscottite, with electrum and minor pyrite, chalcopyrite, naumannite, galena, and sphalerite. The major veins formed from repeated episodes of boiling and strong fluid flow inferred from bands of quartz, adularia, and smectite with bladed quartz, columnar adularia, and truscottite.

scholarly journals The Relationship between Fluid Flow, Structures, and Depositional Architecture in Sedimentary Rocks: An Example-Based Overview

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-19 ◽  
Author(s):  
Vilde Dimmen ◽  
Atle Rotevatn ◽  
Casey W. Nixon
Keyword(s):  
Fluid Flow ◽  
Sedimentary Rocks ◽  
Structure Type ◽  
Mineral Dissolution ◽  
Rock Properties ◽  
Hydrocarbon Migration ◽  
Geological Processes ◽  
Wide Range ◽  
Depositional Architecture ◽  
The Relationship

Fluid flow in the subsurface is fundamental in a variety of geological processes including volcanism, metamorphism, and mineral dissolution and precipitation. It is also of economic and societal significance given its relevance, for example, within groundwater and contaminant transport, hydrocarbon migration, and precipitation of ore-forming minerals. In this example-based overview, we use the distribution of iron oxide precipitates as a proxy for palaeofluid flow to investigate the relationship between fluid flow, geological structures, and depositional architecture in sedimentary rocks. We analyse and discuss a number of outcrop examples from sandstones and carbonate rocks in New Zealand, Malta, and Utah (USA), showing controls on fluid flow ranging from simple geological heterogeneities to more complex networks of structures. Based on our observations and review of a wide range of the published literature, we conclude that flow within structures and networks is primarily controlled by structure type (e.g., joint and deformation band), geometry (e.g., length and orientation), connectivity (i.e., number of connections in a network), kinematics (e.g., dilation and compaction), and interactions (e.g., relays and intersections) within the network. Additionally, host rock properties and depositional architecture represent important controls on flow and may interfere to create hybrid networks, which are networks of combined structural and stratal conduits for flow.

Paleomagnetism of the mid-Cretaceous gem-bearing pegmatite dikes of San Diego County, California, USA

2009 ◽  
Vol 46 (9) ◽  
pp. 675-687 ◽  
Author(s):  
D. T.A. Symons ◽  
T. E. Smith ◽  
K. Kawasaki ◽  
M. J. Walawender
Keyword(s):  
Fluid Flow ◽  
Gulf Of California ◽  
Remanent Magnetization ◽  
Sedimentary Rocks ◽  
Economic Importance ◽  
San Diego County ◽  
Magnetization Direction ◽  
Western Zone ◽  
Stable Characteristic ◽  
Tectonic Boundary

Pegmatite dikes in the Peninsular Ranges batholith of southwestern California have produced spectacular crystals of semiprecious and precious minerals for over a century. Aside from their economic importance, these dikes straddle a major tectonic boundary and were used to test hypotheses related to the timing and development of this composite batholith. Paleomagnetic analysis of 252 specimens from 20 sites (12 and 8 sites in the western and eastern zones of the batholith, respectively, from 11 mines in five dike districts) isolated a stable characteristic remanent magnetization direction at 19 sites. The site mean directions for the western and eastern zones are statistically indistinguishable at 95% confidence, supporting petrologic and geochemical arguments that the dikes of the two zones are coeval and cogenetic. After correction for the Neogene opening of the Gulf of California, the paleopole for all 19 site mean directions is indistinguishable from the 94 Ma reference paleopole for North America and supports hypotheses that (1) the dikes are genetically related to intrusion of the La Posta-type plutons; (2) the batholith was already assembled beside the northwestern coastline of Mexico at 94 Ma; (3) ENE-side-up tilting of fault blocks in the batholith’s western zone ended by ∼94 Ma; and (4) the far-sided and clockwise-rotated discordant paleopoles found commonly in Late Cretaceous and younger sedimentary rocks of the batholith’s region are mostly the result of inclination-flattening of the remanence and (or) remagnetization by fluid flow, creating a secondary remanence, excluding Neogene tectonic rotations.

Analysis of Au content in sedimentary rocks around the Hishikari gold deposit, Japan

2005 ◽  
pp. 585-588
Author(s):  
Kenzo Sanamatsu ◽  
Akira Imai ◽  
Koichiro Watanabe ◽  
Tetsuya Nakanishi
Keyword(s):  
Gold Deposit ◽  
Sedimentary Rocks

Electromagnetic characterization of epithermal gold deposits: A case study from the Tuoniuhe gold deposit, Northeast China

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. B49-B62 ◽  
Author(s):  
Shan Xu ◽  
Fengming Xu ◽  
Xiangyun Hu ◽  
Qun Zhu ◽  
Yuandong Zhao ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Northeast China ◽  
Depth Interval ◽  
Alteration Zone ◽  
Magnetic Survey ◽  
Depth Range ◽  
Epithermal Gold ◽  
Low Resistivity ◽  
Resistivity Model ◽  
Gold Bearing

A high-resolution electromagnetic study has helped to define the mineralization and alteration system of the Cretaceous volcano-sedimentary hosted epithermal gold (Au) deposit in Tuoniuhe, northeast China. Audio-magnetotelluric (AMT) array data were acquired to map the regional resistivity structure of the Mesozoic volcanic field, whereas an AMT profile and a ground magnetic survey line with denser site spacing were deployed across the deposit to image the alteration and mineralization system. The electrical resistivity model from 2D inversion of the AMT profile data reveals a low-resistivity (approximately [Formula: see text]) cover from the surface to a depth of 0.1 km, which is likely caused by clay and sulfide minerals in the subaerial alteration zone. The magnetic survey and a geologic borehole log assisted in outlining a zone of tonalite and andesite with silicification in the depth interval of 0.1–0.3 km, featuring high resistivity ([Formula: see text]) and high magnetization ([Formula: see text]). This zone is a potential gold target bounded by two channels of moderate resistivity (approximately [Formula: see text]) to its northwest and southeast. The two channels possibly coincide with breccia pipes with fractured stockworks and high permeability to allow gold-bearing fluids to move toward the surface. The 2D and 3D resistivity models reveal regions of low resistivity ([Formula: see text]) at the depth range of 0.5–1.0 km beneath the Cretaceous calderas and the deposit, which might be related to magmatic cryptoexplosion breccia. In the 2D resistivity model, this magmatic cryptoexplosion breccia zone connects to the subaerial alteration zone through the two breccia pipes, indicative of a circulation system of gold-bearing fluids. Given the coincidence of Cretaceous volcanism and the age of mineralization, the Cretaceous magma is inferred to have supplied heat that drove the convective hydrothermal activity and also was a source of magmatic fluids that led to the development of the Tuoniuhe epithermal gold deposit.

Ore mineralogy of the Rodu-Frasin Au-Ag deposit, Metaliferi Mountains, Romania

2020 ◽  
Author(s):  
Iatan Elena-Luisa
Keyword(s):  
Base Metal ◽  
Sedimentary Rocks ◽  
Metal Sulfides ◽  
Volcanic Structure ◽  
The North ◽  
Research And Innovation ◽  
Base Metal Sulfides ◽  
The Individual ◽  
Individual Grains ◽  
Low Sulfidation

<p>The Rodu-Frasin Neogene volcanic structure and associated Au-Ag mineralization are located in the north-eastern part of the Metaliferi Mountains, being part of the Baia de Aries - Rosia - Bucium metallogenetic district of the "Golden Quadrilateral".</p><p>The Rodu-Frasin region's geology consists mainly of Frasin dacite dyke and dome, polymictic volcanic and phreatomagmatic breccias and related volcano-sedimentary deposits, Badenian volcanic and sedimentary rocks, and Cretaceous sedimentary rocks.</p><p>Hydrothermal alteration in the region is pervasive and widespread throughout the volcanic structure and surrounding Cretaceous formation. Five main types of hydrothermal alterations have been described: potassic, propylitic, phyllic, silicic and carbonate. Argillic alteration is present only locally.</p><p>In the area of Rodu-Frasin deposit, the ore occurs in a structurally complex environment, influenced by faults and fractures oriented in two or more directions. Au-Ag-base metals mineralization is genetically associated with hydrothermal breccias and phreatomagmatic fractures.</p><p>Ore minerals consist of sulfides, gold, carbonates, adularia and quartz. They have been prevalently emplaced as veins, breccia bodies and disseminations in open fractures and breccias in the Rodu diatreme, and as stockworks, veins and disseminations in relationship to the Frasin dome structure.</p><p>The mineralized veins contain carbonates, quartz, pyrite, sphalerite, galena, chalcopyrite, tetrahedrite and gold. Magnetite and hematite, probably formed under mesothermal conditions, have been identified only as metasomatic substitutions of possible deep-breaking Cretaceous limestone clasts.</p><p>The deposition of the ore seemed to have a pulsating nature with the evolution taking place, possibly, in three stages to which the following mineral assemblages were described: 1. magnetite, hematite - pyrite, marcasite - quartz and pyrite - quartz ± base metal sulfides, in the first stage (mesothermal?); 2. arsenopyrite, Au - base metal sulfides - quartz - adularia, “chinga”, pyrite, Au - quartz - adularia and base metal sulfides - calcite, aragonite, dolomite, ankerite, ± rhodochrosite ± kutnahorite - quartz - adularia, in the second stage (epithermal low sulfidation) and 3. quartz - pyrite - marcasite - carbonates dominant rhodochrosite - Au and alabandite - rhodochrosite - quartz in the third stage (epithermal low sulfidation).</p><p>Gold is present in various proportions, either as small grains or as sub-microscopic occurrences and has been petrographically identified as electrum. The individual grains in native state have been observed as thin sheets on pyrite, sphalerite, rhodochrosite, calcite and quartz or as short wires and sheets in geodes. Local gold concentrations are common at the intersection of the locally-called “chairs” with “crosses” veins.</p><p><strong>Acknowledgments</strong></p><p>This work was supported by two Romanian Ministry of Research and Innovation grants, CCCDI – UEFISCDI, project number PN-III-P4-ID-PCCF-2016-4-0014 and PN-III-P1-1.2-PCCDI-2017-0346/29, within PNCDI III.</p>

scholarly journals Combined positron emission tomography and computed tomography to visualize and quantify fluid flow in sedimentary rocks

2015 ◽  
Vol 51 (9) ◽  
pp. 7811-7819 ◽  
Author(s):  
M. A. Fernø ◽  
J. Gauteplass ◽  
L. P. Hauge ◽  
G. E. Abell ◽  
T. C. H. Adamsen ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Positron Emission Tomography ◽  
Fluid Flow ◽  
Sedimentary Rocks ◽  
Emission Tomography ◽  
Positron Emission
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