Andreas Dietrich

Dietrich Consulting E.I.R.L. · Geological Mapping Services

The development of new techniques in mineral exploration seems to reduce the need of geological field work and mapping: Data collection can now be done remotely by satellites, drones, and tablet-equipped field assistants, while the geologist assembles data sets with 3D software. The interpretation of complex data sets can be assisted by machine lea...

High-grade epithermal Au–Ag veins of the Vodorazdelnaya district in far eastern Russia are hosted by Early Cretaceous volcanic rocks of the Tytylveem belt. The largest deposit is Zone 37, a 1-km long, northeast-striking vein that is up to 35-m wide, containing at least 32 t Au. The main shoot consists of crustiform—colloform banded quartz-chalcedon...

The San José mining district in the northwestern Deseado Massif of southern Argentina produces silver and gold from intermediate sulfidation style epithermal veins. The district geology is characterized by a subhorizontal sequence of Jurassic volcanic rocks, dominated by volcanogenic agglomerates and lava flows of andesitic to basaltic andesitic co...

The Deseado Massif in southernmost Argentina is an exposed block of Mesozoic volcanic rocks that host low- to intermediate-sulfidation style Au-Ag epithermal systems (Schalamuk et al. 1997). Mining is in several districts such as Cerro Vanguardia, Manantial Espejo, Martha, Cerro Negro, San José, Don Nicolas, Cerro Moro, and Cose. Other systems are...

The Dvoinoye district is located in the Chukotka Autonomous Okrug in far eastern Russia, north of the Arctic Circle. The epithermal "Zone 37" vein is the largest deposit in the district. High grade Au-Ag vein mineralization was initially mined in the period 1996 to 2007 via small pits.Underground development of the Zone 37 vein started in 2011, wit...

The San José district is located in the northwest part of the Deseado massif and hosts a number of epithermal Ag–Au quartz veins of intermediate sulfidation style, including the Huevos Verdes vein system. Veins are hosted by andesitic rocks of the Bajo Pobre Formation and locally by rhyodacitic pyroclastic rocks of the Chon Aike Formation. New 40Ar...

Quartz-hosted melt inclusions from latite dykes of the Eocene El Salvador copper porphyry system in northern Chile display wide ranges in both boron concentration (15–155 p.p.m. B) and isotope composition (δ11B −7 to +12‰; n = 10), likely reflecting slab-derived fluid input from seawater-altered oceanic crust. In contrast, the major Miocene tin-sil...

In situ U-Pb SHRIMP analysis of hydrothermal monazite virtually free of Th and poor in U (<0.2 ppm Th, 40-103 ppm U) from the world-class Llallagua tin porphyry deposit in Bolivia defines a mineralization age of 23.4 ± 2.2 Ma (MSWD 0.48) confirming earlier K-Ar sericite alteration age data. These ages are, however, in contrast with a weighted mean...

The emerging Selene mining district in southern Perú is in a Miocene volcanic center and inferred caldera complex. A set of two elliptical ring structures approximately 5–7 km and 13 km in diameter, developed in pyroclastic rocks and interpreted as a caldera setting, encircle a central stratovolcano and most mineralized systems of the district incl...

Adakite-like features are recognized in the Late Miocene (~10Ma) porphyritic intrusions of the Los Pelambres giant porphyry copper deposit, central Chile (32S). Located within the southern portion of the flat-slab segment (28–33S) of the Chilean Andes, the Al- and Na-rich porphyries of Los Pelambres display distinctly higher Sr/Y (~100–300) and LaN...

Melt inclusions in quartz phenocrysts from the El Salvador copper porphyry system (northern Chile) have a highly fractionated rhyolitic composition, distinctly different from the andesitic host rock. The melt inclusions composition is comparable with quartz-sanidine rhyolitic porphyries (45 to 41.5 Ma) suggesting the intrusion of mafic melt (andesi...

Tourmaline alteration and high boron contents are typical features of the magmatic-hydrothermal systems of the Bolivian tin province. The average boron content in melt inclusions of quartz phenocrysts from tin porphyry systems is 225 ppm (1σ-variation range: 110–420 ppm; n=12) and suggests a magmatic boron input to the hydrothermal tin systems, and...

The Miocene tin porphyry systems of Llallagua, Chorolque, and Cerro Rico have a moderately fractionated rhyodacite to dacite bulk rock composition. Ta, Zr, and TiO 2 concentrations are close to average upper crustal values. Hydrothermal overprint is reflected by strong enrichment of B, Bi, and Sn (>100 times upper crust) and by moderate enrichment...

Metal enrichment to ore grade is the ultimate outgrowth of large-scale and long-term fractionation processes of the thermally driven and unique water-cooled geological evolution of the Earth. Silicic magmatism along convergent margins is the most important lithospheric fractionation process for the formation of the continental crust and porphyry/in...

Micron-sized melt inclusions (MI), trapped in host quartz crystals from rocks of magmatic systems, probe the evolution of ore deposits. PIXE in combination with NRA of light element concentrations provide a nearly complete database for geochemical characterisation. Tin deposits are usually associated with highly fractionated granitic magmatism. The...

Metallogeny, geochemistry and melt inclusion studies of tin porphyry and copper porphyry systems of the Central Andes (Bolivia, Chile). Porphyry-type deposits belong to the economically most important features of the central Andean Cu-(Mo-Au) belt and the Sn-(W-Ag-Bi) province. The geochemistry of bulk rock samples (XRF, INAA, ICP-MS, AAS) and mel...

Melt inclusions in quartz phenocrysts from Bolivian tin-porphyry systems have a highly fractionated rhyolitic composition, distinctly different from the rhyodacitic bulk rock. The melt-inclusion geochemistry (electron and proton microprobe analysis) points to mixing of a highly evolved rhyolitic melt with andesitic to basaltic melt portions in an u...

Zugl.: Clausthal, Techn. Univ., Diss., 1999.