Eva Schandl, PhD

economic geologist

From the very beginning of her career, Eva was “hooked on” hydrothermal ore deposits, ore-related alteration, and the nature of mineralizing fluids. Several of her publications, research and contract work reflect this interest (see: List of Publications).

Hydrothermal ore deposits are the most enigmatic deposits of the world. They encompass gold, base metals, base metal sulfides, molybdenum, uranium, Ni-laterite, Ni-alloys, several of the RE, PGM deposits and many others. They precipitate from fluids of variable temperature and chemistry, they occur in ancient and modern environments, and are hosted by a variety of rock types. One of their characteristic feature is, the ubiquitous presence of replacement minerals in the host rocks, which often form an ore-specific alteration halo. In metamorphic environments it is challenging to distinguish between alteration assemblages that represent physicochemical conditions during ore deposition, and alteration assemblages that merely represent post-depositional conditions. Understanding processes that operate during ore formation requires an integrated study of mineralogy, mineral chemistry, textural relationships, and whole-rock geochemistry. In complex hydrothermal systems, fluid inclusion microthermometry plays an important part in the study.

During the past 25 years she and her co-investigators often traveled in uncharted territories, and were the “first” to apply analytical methods to a number of unsolved geological problems.

 Innovative Studies

Her research group (Schandl, Gorton & Davis) was the first to age-date alteration haloes around Archean VMS deposits and to suggest that the present replacement minerals are not syn-volcanic, but metamorphic in origin. To demonstrate this hypothesis, U-Pb dating was done on single grains of low-Th hydrothermal monazite and xenotime which were identified as accessory minerals contemporaneous with chlorite and sericite in the alteration haloes of several Archean VMS deposits in the Superior Province of Canada. The ages obtained on the RE phosphates were ca. 50-70 m.y. younger than the age of the host rhyolite and the inferred age of the ore. In summary, their findings challenge previously held theories, that 1) the chemical and isotopic composition of ore-associated hydrothermal fluids can be calculated,  using the present alteration assemblages and  2) well documented REE mobility around VMS deposits was contemporaneous with synvolcanic hydrothermal alteration. Evidently, the much younger age of the rare earth minerals indicate post-ore REE moibility, suggesting that the  present alteration assemblages do not reflect physicochemical conditions that existed during ore deposition.

Their group was also the first to determine the precise U-Pb age of regionally widespread albite alteration spatially associated with gold mineralization in the Superior Province of Canada (Schandl, Davis & Gorton). They dated low-Th hydrothermal monazites in albitized sediments that host a number of gold deposits in the Quetico subprovince of the Superior Province. U-Pb dating was done on single grains of hydrothermal monazites that were shown to be contemporaneous with the albite. These monazites are locally abundant and are restricted to the albitized rocks. Their age corresponds to the time of well-documented alkaline magmatism in the area, suggesting that the Na-rich fluids were most likely related to deep-seated alkaline magmatism.

Schandl, Wicks & O’Hanley, established a precise geothermometer for serpentinization by obtaining fluid inclusion data on calc-silicates in rodingites that crystallized during the replacement of ultramafic hosts by serpentine. Because of the symbiotic relationship between rodingite minerals and serpentine, the group demonstrated that microthermometry and gas chromatography on fluid inclusions in rodingite minerals provide reliable information on the temperature and chemistry of the serpeninizing fluids. As part of the study, they published the first comprehensive paper on the mineralogy and chemistry of Archean rodingites in variably serpentinized ultramafic rocks of the Abitibi greenstone belt.

As the sole petrologist on ODP Cruise Leg 113 to Antarctica Eva had the unique opportunity to study the only basalts ever recovered from Maud Rise, located in the Weddell Sea of Antarctica. Her group identified the rocks as mantle-derived, highly vesicular alkali basalts that were generated by hot-spot activities (Schandl, Gorton & Wicks). The 2m long basaltic core, which consists of two flow tops, contains several large mantle xenoliths (orthopyroxene, olivine, chromite and apatite). The chemistry and mineralogy of the basalt provides important information on the tectonic evolution of the South Atlantic Ocean, supporting the theory that during the Cretaceous, Maud Rise was part of the Agulhas Plateau and separated from it during a ridge jump (cf. H.R. Kim et al., 2005).

 In-depth Studies

Selected in-depth studies by Schandl & Co-Investigators are listed below:

Kidd Creek Volcanogenic massive sulfide deposit (VMS), Timmins, Ontario: Detailed study of 1) mineralogy and geochemistry of the rhyolite and underlying ultramafic rocks, 2). REE mobility in the alteration halo, 4) the geochronology of the alteration by U-Pb and Ar40/Ar30 methods on monazite and fuchsite, respectively, and 3) fluid inclusion microthermometry and stable isotope geochemistry of carbonates in the ultramafic rocks and rhyolite.

Sullivan SEDEX deposit, British Columbia: Study of the mineralogy, alteration and geochemistry of the Aldridge sediments. Established REE mobility in altered and mineralized rocks, age-dated the Moyie sills in the mine (U-Pb) and the chlorite alteration by titanite.

Munro asbestos mine, Munro Township, Ontario: Study of the mineralogy and geochemistry of the ultramafic rocks, and fluid inclusion – stable isotope study of carbonates in the partly serpentinized ultramafic rocks.

Slade-Forbes asbestos mine, Deloro Township, Ontario: Study of the mineralogy and geochemistry of serpentinized and talc-carbonate altered ultramafic rocks, and fluid inclusion and stable isotope study on the carbonates.

David Bell gold mine, Hemlo, Ontario: A study of the mineralogy and geochemistry of mineralized rocks that host the gold in the mine, with particular emphasis on REE minerels  aaociated with gold. Sb-rich ultramafic lamprophyre dike was discovered within the Sb-enriched mineralized host rocks.

Talc deposits of the Eastern Desert, Egypt: Detailed study of the mineralogy and geochemistry of metamorphosed talc-rich and calc-silicate-rich rocks at several talc deposits in the eastern Desert. The study suggests that the present alteration assemblages at the talc mines probably represent an ancient metamorphosed carbonate horizon.

High temperature brine in mineralized rocks in the Sudbury area: Fluid inclusion and mineralogical studies demonstrated the existence of  high temperature brine in gold and base-metal-rich quartz veins within altered Huronian sediments ca. 30 km northeast and 40 km southwest of the Sudbury Igneous Complex.

Detailed studies of the mineralogy, geochemistry and alteration of the Geco and Winston Lake VMS deposits in the Supeior Province, Ontario, Canada: Documented extreme REE mobility at Winston Lake in the altered rhyolite and basalts, the latter of which contains and abundance of Th-poor hydrothermal monazite and xenotime. Detailed mineralogical and geochemical studies demonstrated that the REE were released from the rhyolite (or volcanic glass) during metamorphic recrystallization, and precipitated the rare earth minerals, monazite end xenotime in the overlying mafic basalts / tuffs. The U-Pb age of the phosphates is consistent with their crystallization during regional metamorphism.

 Research Cruises

Eva’s interest in seafloor geology and associated hydrothermal alteration led to her participation in three international research cruises.

She was part of the scientific party (as petrologist) on board of the research vessel, Joides Resolution, ODP Leg 113, to Weddell Sea, Antarctica. The primary objective of the cruise was, to identify climatic changes in the Antarctic region through the study of biostratigraphy, biogeography and isotopes. Recovering alkali basalts on the Maud Rise was an added bonus to the sediment-dominated cruise. The 9-week long journey began in Punta Arenas, Chile and finished in the Falkland Islands. The Resolution sailed around the Weddell Sea and drilled the sediments at nine sites. Throughout the cruise the ship was accompanied by an ice-support vessel, the Danish Maersk Master, and at one point it met up with the German icebreaker Polarstern. The Resolution crew was invited on board for a tour of their ship – and for good cheer. During the 9-week long cruise floating icebergs passed by, friendly penguins stared at the ship from icebergs, and hungry, curious whales circled around the Resolution. While passing the Antarctic Circle, everyone was treated to a spectacular celebratory banquet by the Portuguese cooking crew.

As the only Canadian, Eva was a metamorphic petrologist on board of the Joides Resolution ODP Leg 140. The ship sailed from Victoria, British Columbia to the Costa Rica Rift Zone in the Indian Ocean. The aim of the cruise was, to clean and deepen an earlier hole (504B) and sample the transition zone in the sheeted diabase dikes. The crew deepened the hole to 2 km, which at that time, was the deepest hole drilled into the ocean floor. The  2 month-long trip ended in Balboa, Panama. Entering the Panama Canal was quite an event, not without some problems and unexpected delays.

She was a member of the scientific party on the British Antarctic Survey vessel – RRS James Clark Ross (JR-31 Leg 1) that sailed from Cape Town, South Africa to the Atlantis Bank – exploring a large gabbro massif in the Southwest Indian Ocean. The cruise was led by two high-profile co-chief scientists, Dr. Paul Robinson of Dalhousie University, Halifax and Dr. Henry Dick of Woods Hole, Oceanographic Institution, Massachusetts. The crew shallow drilled and dredged the seafloor, and with the help of submersible ROPOS (Remotely Operated Platform for Ocean Science) a whole new world of underwater geology and underwater life opened up. The four week journey ended at Reunion Island. An added bonus to the trip was, a midnight visit (on foot) to the active volcano fields. A spectacular display of red-hot molten lava lit up the skies in the distance as the party tried to navigate in the dark on a ragged terrain of hardened, black basalts. Some  lost the power on their night-vision goggle – which added to the excitement, making navigation more challenging!

A Memorable Field Trip: Eastern Desert, Egypt

As an invited guest of the University of Assiut in Egypt, Eva gave a well received presentation at the First International Conference of African Geology, on the origin of talc deposits in the Eastern Desert. Based on detailed mineralogical, geochemical investigation and field relationships, she suggested that some of the talc deposits of the Eastern Desert most likely represent an ancient metamorphosed carbonate horizon. A private five-day field trip (consisting of two land rovers and four helpers) was organized by Dr. Nadia Sharara (Professor of economic geology at the University of Assiut). Driving along the Red Sea, and visiting a number of talc deposits in the Eastern Desert, the group collected samples from several deposits. The trip resulted in their collaboration on two papers. During the 2 weeks stay in Egypt, she was treated to the wonderful hospitality of the university of Assiut, the Department of Geology, and of Professor Sharara. The trips to the Valley of the Kings, Valley of the Queens, the Karnak Temple, the Museum of Cairo, the pyramids, and the boat ride on the River Nile were unforgettable