Franz Michael Meyer - Academia.edu (original) (raw)

Papers by Franz Michael Meyer

Die Betriebsbedingungen der Sonde lagen bei einer Beschleunigungsspannung von 15 kV und einem Pro... more Die Betriebsbedingungen der Sonde lagen bei einer Beschleunigungsspannung von 15 kV und einem Probenstrom von 23 nA. Der Strahldurchmesser variierte nach Art der zu messenden Mineralphase. Für Karbonate (Calcit, Dolomit, Fe-Dolomit und Ankerit) wurde mit einem Strahlendurchmesser von 10 µm gearbeitet, um zum einen ein zu starkes Ausbrennen der Probe zu vermeiden und zum anderen reichte der Durchmesser

Placer gold has been discovered in Bombana, SE-Sulawesi, Indonesia. The placer gold is not associ... more Placer gold has been discovered in Bombana, SE-Sulawesi, Indonesia. The placer gold is not associated with volcanic rock-related gold deposits. This paper discusses the primary gold mineralization as the source of the placer gold. The placer gold is possibly derived from gold-bearing quartz veins hosted by Pompangeo Metamorphic Complex (PMC). Pyrite, chalcopyrite, cinnabar, stibnite and tripuhyite are present. Sheared, segmented vein varies in thickness from 2 cm to 2 m. The veins contain erratic gold in various grades from below detection limit (0.005 g/t) to 134 g/t. At least three generations of veins are identified. The first is parallel to the foliations, the second crosscuts the first generation of veins/foliations, and the third is of laminated deformed quartz+calcite veins at the late stage. The first veins are mostly massive to crystalline, occasionally brecciated and sigmoidal, whereas the second veins are narrower than the first and relatively brecciated. Gold grades in t...

Buletin Sumber Daya Geologi, 2014

Many Tertiary hydrothermal altered dioritic composition intrusive rocks were found at the Randu K... more Many Tertiary hydrothermal altered dioritic composition intrusive rocks were found at the Randu Kuning area and its vicinity, Selogiri, including hornblende microdiorite, hornblende-pyroxene diorite and quartz diorite. The hydrothermal fluids which responsible for the alteration and mineralization at the area is associated with the occurence of the horblende microdiorite intrusion. The alteration zone at the Randu Kuning area and its vicinity can be divided intoseveral hydrothermal alteration zones, such as potassic (magnetite-biotite-K feldspar), prophyllitic (chlorite-magnetite-epidote-carbonate), phyllic (quartz-sericite-chlorite) and argillic (clay mineral-sericite). The alteration pattern in the Randu Kuning porphyry Cu-Au deposit is tipically a diorite model characterising by the domination of potassic alteration and prophyllitic zone. Phyllic and argillic alteration types are restrictive found within the fault zones. A lot of porphyry vein types were found and observed at the...

Journal of Asian Earth Sciences, 2007

Geologische Rundschau, 1999

Indonesian Journal on Geoscience, 2011

Minerals

This review compares genetic parameters of 12 orogenic gold deposits. The set of examples is cons... more This review compares genetic parameters of 12 orogenic gold deposits. The set of examples is considered to represent largely the variability of orogenic gold deposit (OGD) characteristics. The data are presented in tables and include following definitive parameters: regional geologic settings, nature of hosts rocks and mineralization, ore controlling structures, ages of host rocks and mineralization and timing of mineralization relative to metamorphism, hydrothermal alteration mineralogy and ore mineral assemblages, isotopic signatures, physical conditions of ore formation and proposed origin of ore fluids aa well as gold reserves, production, and grades. This allows comparison of deposits from different geologic terrains having different ages and formed under different P-T conditions. The data are further discussed before the background of the orogenic gold system and the crustal metamorphic models that provide different scenarios to explain the source of ore fluids. The orogenic g...

Economic Geology, 2004

The Ajjanahalli gold mine is spatially associated with a Late Archean craton-scale shear zone in ... more The Ajjanahalli gold mine is spatially associated with a Late Archean craton-scale shear zone in the eastern Chitradurga greenstone belt of the Dharwar craton, India. Gold mineralization is hosted by an ~100-m-wide antiform in a banded iron formation. Original magnetite and siderite are replaced by a peak metamorphic alteration assemblage of chlorite, stilpnomelane, minnesotaite, sericite, ankerite, arsenopyrite, pyrite, pyrrhotite, and gold at ca. 300°to 350°C. Elements enriched in the banded iron formation include Ca, Mg, C, S, Au, As, Bi, Cu, Sb, Zn, Pb, Se, Ag, and Te, whereas in the wall rocks As, Cu, Zn, Bi, Ag, and Au are only slightly enriched. Strontium correlates with CaO, MgO, CO 2 , and As, which indicates cogenetic formation of arsenopyrite and Mg-Ca carbonates. The greater extent of alteration in the Fe-rich banded iron formation layers than in the wall rock reflects the greater reactivity of the banded iron formation layers. The ore fluids, as interpreted from their isotopic composition (δ 18 O = 6.5-8.5‰; initial 87 Sr/ 86 Sr = 0.7068-0.7078), formed by metamorphic devolatilization of deeper levels of the Chitradurga greenstone belt. Arsenopyrite, chalcopyrite, and pyrrhotite have δ 34 S values within a narrow range between 2.1 and 2.7 per mil, consistent with a sulfur source in Chitradurga greenstone belt lithologies. Based on spatial and temporal relationships between mineralization, local structure development, and sinistral strike-slip deformation in the shear zone at the eastern contact of the Chitradurga greenstone belt, we suggest that the Ajjanahalli gold mineralization formed by fluid infiltration into a low strain area within the first-order structure. The ore fluids were transported along this shear zone into relatively shallow crustal levels during lateral terrane accretion and a change from thrust to transcurrent tectonics. Based on this model of fluid flow, exploration should focus on similar low strain areas or potentially connected higher order splays of the first-order shear zone.

Alkaline rocks are worldwide observed as hosts for rare metal (Zr-REE-Nb) minerals. The classific... more Alkaline rocks are worldwide observed as hosts for rare metal (Zr-REE-Nb) minerals. The classification of the ore bearing rock type is challenging due to the fact that textures and mineral assemblage are obscured by post-magmatic alteration. In addition, the alteration causes fine and intricate intergrowth of the ore minerals with associated gangue. Hence, intensive comminution is necessary to liberate the ore minerals, which is one parameter hampering the economical use of this deposit type. This study provides a quantitative mineralogical investigation of the ore bearing rock suite at Khalzan Buregtei as an example of rare metal deposits. R1-R2 multication parameters are shown to be highly appropriate as quantitative mineralogical indicators based on readily available major element datasets to visualize and quantify alteration types of the ore bearing rock suite. The ore minerals were found to be associated with a cluster-forming assemblage of post-magmatic phases. Automated mineralogy was applied to quantify the textural properties of the ore mineral clusters. This finding permits efficient pre-concentration of rare metal ore at coarser particle size fraction, requiring less energy consuming comminution.

The Seridune district consists of an Eocene volcanic andesite succession with a gently northeast ... more The Seridune district consists of an Eocene volcanic andesite succession with a gently northeast dipping, which was intruded by at least two phases of copper-bearing granodiorite porphyries. They are subsequently referred to as “granodiorite stock”, and affiliated “granodiorite dikes” (Late Miocene). Furthermore, a late barren dike of intergranular quartz monzonite also intruded into the volcanic andesite. A succession of volcanic dacite lava (Pliocene) overlies the intrusions mainly at the west part of the Seridune district. The volcanic andesite rocks are characterized by plagioclase grains (An85-35) and are classified as low-K calc-alkaline rocks. The least altered porphyritic granodiorite contains zoned plagioclase (An50-20) and hornblende with quartz, biotite, magnetite and minor ilmenite. These mineral phases are set in an interstitial medium-grained quartz and plagioclase groundmass. The porphyritic granodiorite is discriminated as a medium-high-K calc-alkaline suite. The int...

Geological Survey of Denmark and Greenland Bulletin, 1969

During field work in 2008, the Geological Survey of Denmark and Greenland investigated the gold p... more During field work in 2008, the Geological Survey of Denmark and Greenland investigated the gold potential of hydrothermal vein systems in the Nuuk region of the Archaean North Atlantic craton. A new gold occurrence was discovered on the island of Qilanngaarsuit, 35 km south of Nuuk. Two cross sections through hydrothermal alteration zones, that locally contain up to 672 ppb Au, were mapped and sampled in detail. In this study, we present petrological and geochemical data in order to constrain the conditions for ore formation and transport of elements during fluid–rock interaction.

Journal of Applied Geology, 2015

The Randu Kuning prospect is situated at Selogiri area, Wonogiri, Central Java, Indonesia. This l... more The Randu Kuning prospect is situated at Selogiri area, Wonogiri, Central Java, Indonesia. This location is about 40 km to the south-east from Solo city or approximately 70 km east of Yogyakarta city. Many Tertiary dioritic rocks related alterationmineralisation were found at the Randu Kuning area and its vicinity, including hornblende microdiorite, hornblende-pyroxene diorite and quartz diorite. Mineralisation type of the Randu Kuning prospect was interpreted as porphyry Cu-Au and a number epithermal Au-base metals deposits in its surrounding. The closed existing of porphyry Cu-Au and epithermal Au-base metals type deposits at the Randu Kuning area produced a very complex of veins and hydrothermal breccias crosscutting relationship. A lot of porphyry veins types were found and observed at the Randu Kuning area, and classiﬁed into at least seven types. Most of the porphyry veins were cross cut by epithermal type veins. Many epithermal veins also are found and crosscut into deeply po...

Journal of Applied Geology, 2015

Low suphidation (LS) epithermal gold deposits were recently found in the Paningkaban area, Centra... more Low suphidation (LS) epithermal gold deposits were recently found in the Paningkaban area, Central Java province, Indonesia, with more than ﬁve hundred artisanal gold miners currently operating in the area. This study is aimed to understand the geological factors controlling the gold mineralization and to characterize the alteration and ore mineralogy of the deposit. Several epithermal veins/veinlets trending N–S, NW–SE, and NE–SW are hosted by Tertiary turbiditic volcanoclastic sedimentary rocks of the Halang formation. This formation is composed of looping gradation of sandstone and siltstone units. Pre- and syn-mineralization structures such as extension joints, normal sinitral fault and sinitral fault control the gold mineralization. Fault movements formed dilational jogs manifested by NW-SE-trending en-echelon tension gash veins. Four main alteration zones are identiﬁed: (a) phyllic, (b) argillic, (c) sub propylitic and (d) weak subpropylitic. Ore minerals consist of native gol...

Pesquisas em Geociências, 2005

The petrography and chemistry of epidote and amphibole from the Rio Espinharas hybrid complex (RE... more The petrography and chemistry of epidote and amphibole from the Rio Espinharas hybrid complex (REHC), northeastern Brazil are reported. The Rio Espinharas complex is composed of an intimate association of diorite to shoshonitic metaluminous quartzmonzonite to slightly peraluminous syenogranite. The epidote shows four textural relationships: three are primary and one is resulting from sub-solidus reaction. Euhedral epidote is dispersed and associated mainly with biotite and amphibole. In some cases euhedral crystals of the epidote contain allanite cores, which are subhedral to anhedral and constitute in average less than 20% of the whole grain. The contact between primary epidote and plagioclase is corroded, suggesting reaction with the host-magma. Secondary anhedral epidote is rare and results from plagioclase alteration. The preservation of magmatic epidote in granitic rocks emplaced in the upper crust is attributed to rapid magma ascent, which implies fast upward transport probabl...

The Siegerland District is located in the fold-and-thrust-belt of the Rhenish Massif and hosts va... more The Siegerland District is located in the fold-and-thrust-belt of the Rhenish Massif and hosts various syn-late orogenic vein-hosted hydrothermal mineralization types. Peak-metamorphism and deformation occurred at 312-316 ± 10 Ma (Ahrendt et al., 1978) at pT-conditions of 280-320 • C and 0.7-1.4 kbar (Hein, 1993). The district is known for synorogenic siderite-quartz mineralization formed during peak-metamorphic conditions. At least 4 syn-late orogenic mineralization types are distinguished: Co-Ni-Cu-Au, Pb-Zn-Cu, Sb-Au and hematitedigenite-bornite mineralization (Hellmann et al., 2012b). Co-Ni-Cu-Au mineralization of the Siegerland District belongs to the recently defined class of metasediment hosted synorogenic Co-Cu-Au deposits (i.e. Slack et al, 2010). Ore minerals are Fe-Co-Ni sulpharsenides, bearing invisible gold, chalcopyrite, and minor As-bearing pyrite. The gangue is quartz. The alteration mineralogy comprises chlorite, illite-muscovite and quartz. The epigenetic quartz veins are closely related to the formation of reverse faults (Hellmann et al., 2011a). Microthermometric studies of fluid inclusions concerning the relationship between mineralization and microstructures have not been done so far for this deposit-class and this will be addressed here. Fluid inclusions are investigated in hydrothermally formed vein-quartz, selected from Co-Ni-Cu-Au mineralization bearing veins showing only minor overprints by later mineralization types. Two quartz generations are distinguished: subhedral quartz-I showing growth zonation and fine grained, recrystallized-and newly formed quartz-II grains forming irregular masses and fracture fillings in quartz-I. Co-Ni-Fe sulpharsenides and chalcopyrite are closely intergrown with quartz-II, implying their contemperaneous formation. However, fluid inclusions in quartz-II are often small, therefore fluid inclusions in quartz-I have been mostly investigated. In total, 180 inclusions from 4 different deposits have been studied. The fluid inclusions are located on healed intragranular trails in quartz-I grains and subordinate in quartz-II. The inclusions are 5-20 [U+F06D]m in size and are aqueous biphase (L+V) showing a constant L/V ratio of 4. Homogenization is always to the liquid with Th (L) = 170-250 • C (202 • C mean). The salinity is moderate, with a range in Tm between-8 to-3 • C, corresponding to 5-10 mass-% NaCl eq. (8.2 mass-% mean). There is no difference between fluid inclusions investigated in quartz-I and quartz-II. Despite the common occurrence of siderite in synorogenic siderite-quartz-veins, carbonate is absent in the alteration assemblage, implying a low CO 2-activity in the fluids. Isochore calculations, combined with the paleo-geothermal gradient deduced for peak metamorphic conditions (Oncken, 1991) shows that the trapping temperature of the fluid is likely in the range between 220-300 • C. The study shows that Co-Ni-Cu-Au mineralization has formed at the district scale from a relative homogeneous, aqueous fluid of moderate salinity, which may have been derived from the devolatilization of the sedimentary pile in deeper crustal regions.

The Siegerland district is located in the fold-and thrust-belt of the Rhenish Massif and hosts di... more The Siegerland district is located in the fold-and thrust-belt of the Rhenish Massif and hosts diverse syn-to late orogenic mineralization styles. Peak-metamorphism and deformation occurred at 312-316±10 Ma (Ahrendt et al., 1978) at temperature-pressure conditions of 280-320 • C and 0.7-1.4 kbar (Hein, 1993). In addition to syn-orogenic siderite-quartz mineralization at least four different syn-to late orogenic mineralization stages are identified comprising Co-Ni-Cu-Au, Pb-Zn-Cu, Sb-Au, and hematite-digenite-bornite ores (Hellmann et al., 2012).

Buletin Sumber Daya Geologi, 2014

Journal of Asian Earth Sciences, 2007

Geologische Rundschau, 1999

Indonesian Journal on Geoscience, 2011

Minerals

Economic Geology, 2004

Geological Survey of Denmark and Greenland Bulletin, 1969

Journal of Applied Geology, 2015

Pesquisas em Geociências, 2005