Pierre-Simon Ross

Pierre-Simon Ross
Institut National de la Recherche Scientifique | INRS · Eau Terre Environnement Centre

PhD

About

90
Publications
41,953
Reads
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2,589
Citations
Citations since 2017
27 Research Items
1376 Citations
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Introduction
• I am interested by magma fragmentation and the characteristics of juvenile ash particles • I apply volcanology and geochemistry to the mapping of submarine Archean sequences and the exploration for mineral deposits, including VMS and gold.
Additional affiliations
February 2016 - July 2016
Queensland University of Technology
Position
  • Researcher
Description
  • Sabbatical stay at QUT: worked on felsic maar-diatreme volcanoes
September 2007 - present
Institut National de la Recherche Scientifique
Position
  • Professor
Description
  • Professor of volcanology and economic geology
May 2006 - August 2007
Natural Resources Canada
Position
  • PostDoc Position
Description
  • Volcanology of the Blake River Group, Abitibi Greenstone Belt
Education
June 2002 - June 2005
University of Otago
Field of study
  • Geology
January 2000 - January 2002
Université du Québec à Montréal
Field of study
  • Earth Sciences

Publications

Publications (90)
Article
The Archean Horne 5 deposit, located in the Rouyn-Noranda district in the southern Abitibi greenstone belt, Canada, contains a total resource of 172.4 t Au (5.6 Moz) from 112.7 Mt of ore grading at 1.53 g/t Au. The deposit is part of the Au-rich Horne volcanogenic massive sulfide (VMS) complex that also includes the past-producing Horne mine (i.e.,...
Article
Full-text available
Primary magma fragmentation in “fluid-dominated” (as opposed to “ash-dominated”) lava fountains involves the hydrodynamic breakup of a jet of magma. Lava fountains partly resemble industrial liquid jets issued from a nozzle into a quiescent atmosphere, on which there is a vast literature. Depending on the internal liquid properties, nozzle diameter...
Article
Full-text available
The morphological and textural features of juvenile pyroclasts record crucial details on magma conditions at the time of fragmentation. Their study is therefore essential to better understand the dynamics of explosive eruptions. Unfortunately, the absence of a standardized protocol of investigation hinders data reproducibility and comparison among...
Article
Full-text available
Juvenile pyroclasts, especially in the ash size range, provide important information on primary fragmentation processes, i.e., initial explosive magma fragmentation, and on the state of the magma both prior to and at the point of fragmentation and quenching. There exists an extensive body of literature focusing on the quantification of juvenile par...
Article
Full-text available
Morphometric analyses are based on multiparametric data sets that describe quantitatively the shapes of objects. The stochastic nature of fracture formation processes that break up magma during explosive eruptions yields mixtures of particles that have highly varied shapes. In volcanology, morphometric analysis is applied to these mixtures of parti...
Article
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Quantifying the proportions of certain components in rocks and deposits (modal analysis or componentry) is important in earth sciences. Relevant methods for cross-sections (two- dimensional exposures) of clastic rocks include point counts or line counts. The accuracy of these methods has been supposed to be good in the literature but not necessaril...
Code
The PArticle Shapes and Textures Analyzer (PASTA) project contains tools for the analysis of juvenile pyroclasts for fragmentation studies in Volcanology. The tools are primarily designed to prepare and process SEM-BSE images of particle cross-sections, but the use could be extended to other types of images. Free access on Zenodo.org (see link in...
Article
Full-text available
Round Butte (Hopi Buttes volcanic field, Arizona) exposes a diatreme 170-190 m across, 190 m below the pre-eruptive surface. The central part of the massif is 130-150 m in diameter, displaying 20-30 m-high subvertical cliffs. The well-known layer-cake stratigraphy of the sedimentary rocks of the Colorado Plateau permits identification of the larges...
Article
Full-text available
The Hopi Buttes volcanic field (HBVF) is located on the Colorado Plateau, northern Arizona. In this Miocene volcanic field, the erosion level increases southward, allowing the study of maar-diatreme volcanoes from top (post-eruptive crater infill and ejecta ring) to bottom (lower diatreme). The Twin Peaks volcanic complex consists mostly of two hil...
Article
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The Archean Lemoine volcanogenic massive sulfide (VMS) deposit in the Chibougamau mining district (Abitibi greenstone belt) is one of the richest to have been mined in the world (758,070 t of ore at 4.17% Cu, 9.51% Zn, 4.56 g/t Au, and 83.73 g/t Ag). It is hosted by the ~ 2728 Ma Lemoine Member of the Waconichi Formation. Field mapping, core loggin...
Article
In French Guiana, the Montagne d’Or gold deposit (5 Moz at 1.5 g/t Au) is located in the northern branch of the Rhyacian Paramaca Greenstone Belt. The sulphide deposit is hosted by a south-facing bimodal volcanic and volcaniclastic sequence that is highly strained and affected by a penetrative E-W striking and steeply south-dipping foliation. The v...
Poster
Full-text available
The Hopi Buttes volcanic field (HBVF) in Arizona is principally composed of maar-diatreme volcanoes. This Miocene volcanic field provides excellent exposures from the maar ejecta ring to the deep diatreme. The small but surprisingly complex Round Butte diatreme is located in the southeastern part of the HBVF and crops out ~190 m below the pre-erupt...
Article
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Mining exploration increasingly relies on large, multivariate databases storing data ranging from drill core geochemical analysis to geophysical data or geological descriptions. Utilizing these large datasets to their full potential implies the use of multivariate statistical analysis such as machine learning. The Random Forest algorithm has proved...
Article
Full-text available
Archean greenstone terranes are key to understanding the geological processes active during early Earth history. These areas are also of economic interest due to their association with volcanogenic massive sulphide (VMS) deposits, and several other types of mineral deposits. The Archean Colomb-Chaboullié greenstone belt is located between the Nemis...
Article
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Round Butte is a small but complex Miocene diatreme that crops out ~ 190 m below the pre-eruptive surface, in the southeastern part of the Hopi Buttes volcanic field. Erosional remnants consist of a diatreme 170–190 m in diameter, of which the central 130–150 m is well-exposed in a massif featuring 20–30-m-high sub-vertical cliffs, and a 50-cm-thic...
Poster
Full-text available
Juvenile pyroclasts offer unique insights on the style of magma fragmentation. Observed variations in their morphology (e.g., fluidal versus blocky), crystallinity, vesicularity, and surface features (e.g., stepped features, etc.) have been used to distinguish phreatomagmatic from magmatic explosive activity. This distinction is of primary importan...
Article
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Cathedral Cliff is a well-exposed mid-Tertiary phreatomagmatic diatreme in the Navajo volcanic field, New Mexico. Post-eruptive erosion, estimated between 500 and 1000 m, exposes the deep part of the diatreme. Cathedral Cliff provides an opportunity to examine the transition between the bedded pyroclastic rocks of an upper diatreme and the nonbedde...
Article
Several volcanogenic massive sulfide (VMS) deposits have been mined in the Archean Matagami mining district (Abitibi subprovince, Quebec, Canada), but the volcanology of their host rocks has been little studied. Most VMS lenses are located along a stratigraphic marker known as the Key tuffite. Footwall rocks belong to the Watson Lake Group (tholeii...
Poster
Full-text available
The Hopi Buttes volcanic field (HBVF) is located on the Colorado Plateau in Arizona (USA). This Miocene volcanic field provides excellent exposures of maar-diatreme volcanoes (White and Ross, 2011). In the HBVF, the variable erosion level allows the study of maar-diatremes from top to bottom. Williams (1936) defined the typical Hopi-type neck as a...
Conference Paper
Full-text available
The Miocene Hopi Buttes volcanic field (HBVF) in the Navajo Nation (Arizona, USA) provides excellent exposures of maar-diatreme volcanoes (White and Ross, 2011) at different erosion depths, from the maar ejecta ring and crater infill (White, 1991) to the deep diatreme (Lefebvre et al., 2013). The base of the current exposure at Round Butte, in the...
Conference Paper
Full-text available
The Hopi Buttes volcanic field (HBVF) is located on the Colorado Plateau in Arizona (USA). This Miocene volcanic field provides excellent exposures of maar-diatreme volcanoes (White and Ross, 2011). In the HBVF, the variable erosion level allows the study of maar-diatremes from top to bottom. Williams (1936) defined the typical HBVF volcanic necks...
Article
Full-text available
Classification of rock types using geochemical variables is widely used in geosciences, but most standard classification methods are restricted to the simultaneous use of two or three variables at a time. Machine learning-based methods allow for a multivariate approach to classification problems, potentially increasing classification success rates....
Poster
Full-text available
The Hopi Buttes volcanic field (HBVF) in the Navajo Nation (Arizona, USA) provides excellent exposures of maar-diatreme volcanoes at different erosion depths, from the maar ejecta ring and crater infill (White 1991) to the deep diatreme (Lefebvre et al. 2013). This makes it an ideal locality to better understand eruptive processes for this type of...
Poster
Full-text available
Juvenile pyroclasts come in a range of sizes, shapes, surface features and internal textures (e.g., for basalt, sideromelane versus tachylite). These parameters are influenced by how magma deforms, fragments and cools, which is controlled by factors such as magma viscosity, surface tension, crystallinity, volatile content, and interaction with exte...
Conference Paper
Full-text available
The Cerro Chivo Volcanic Field (CCVF) in Chubut Province dates from the early Tertiary and exposes the subsurface manifestations of basaltic monogenetic volcanoes, mostly of the maar-diatreme type. Documented features include unfragmentated basalt sheets; root zones, where the dikes and/or the country rocks are fragmented, and which may have fed di...
Article
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Recent work is changing our understanding of phreatomagmatic maar-diatreme eruptions and resulting deposits. In previous models, explosions were often inferred to take place only at the base of a diatreme, with progressive downward migration due to a cone of depression in the host aquifer. However, diatremes themselves contain much water that is he...
Article
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Felsic maar-diatreme volcanoes host major ore deposits but have been largely ignored in the volcanology literature, especially for the diatreme portion of the system. Here, we use two Mexican tuff rings as analogs for the maar ejecta ring, new observations from one diatreme, and the economic geology literature on four other mineralized felsic maar-...
Article
Full-text available
Physical property measurements are increasingly important in mining exploration. For density determinations on rocks, one method applicable on exploration drill cores relies on gamma ray attenuation. This non-destructive method is ideal because each measurement takes only 10 s, making it suitable for high-resolution logging. However calibration has...
Article
Multiparameter data on drill cores have a range of useful applications for ore deposit modeling and mineral exploration. Density, magnetic susceptibility, eight major elements, seven trace elements (portable X-ray fluorescence [pXRF]), five mineral groups (near-infrared spectrometry), and average visible light reflectance were determined on rock co...
Article
Full-text available
In mineral exploration, traditional core logging is largely based on the visual inspection of drilled cores, a process which is often subjective and non-reproducible. However, a number of physical, chemical and mineralogical properties of rocks can now be measured at high spatial resolution on drill cores. The resulting large multiparameter databas...
Article
Full-text available
While the relationship between the host-substrate properties and the formation of maar-diatreme volcanoes have been investigated in the past, it remains poorly understood. In order to establish the effects of the qualitative host-substrate properties on crater depth, diameter, morphological features, and sub-surface structures, we present a compari...
Article
Full-text available
One geoscience application of portable XRF (pXRF) technology is acquiring ‘whole-rock’ analyses of unmineralized or weakly mineralized rock cores for major oxides and trace elements, to fill the gaps between traditional laboratory analyses and/or obtain geochemical data more quickly. But the question of whether the samples actually need to be crush...
Conference Paper
Full-text available
The Lalor deposit is a newly developed Volcanogenic Massive Sulphide (VMS) deposit in the Snow Lake camp, Manitoba. The deposit is hosted in a complexly deformed and metamorphosed rock package referred to as the Lalor volcanic succession and located in the VMS-prospective Chisel sequence of the Snow Lake arc assemblage. The Lalor deposit consists o...
Article
Full-text available
The volume, grain size, and depositional facies of material deposited outside an explosion crater, ejecta, are sensitive to the depth of the explosion, the explosion energy, and the presence or absence of a crater before the explosion. We detonate buried chemical explosives as an analog for discrete volcanic explosions in experiments to identify un...
Article
Full-text available
We present results of experiments that use small chemical explosive charges buried in layered aggregates to simulate the effects of subsurface hydrothermal and phreatomagmatic explosions at varying depths and lateral locations, extending earlier experimental results that changed explosion locations only along a vertical axis. The focus is on the re...
Technical Report
Full-text available
The Paleoproterozoic Lalor auriferous volcanogenic massive sulphide deposit, located in the Snow Lake mining camp, Manitoba, is hosted in a complex volcanic package referred to as the Lalor volcanic succession. The deposit consists of stratigraphically and structurally stacked Zn-rich, Au-rich and Au-Cu-rich ore lenses. The host volcanic succession...
Conference Paper
The Lalor volcanogenic massive sulphide deposit is the largest deposit in the Snow Lake mining camp with combined reserves and resources of 25.3 Mt at 0.79% Cu, 5.01% Zn, 2.9 g/t Au and 25.04 g/t Ag. The deposit consists in a series of stratigraphically and structurally stacked base metal-rich, Au-rich and Au-Cu-rich ore lenses. The host volcanic s...
Article
Full-text available
Volcanogenic massive sulfide (VMS) deposits and seafloor massive sulfide (SMS) deposits have a spatial and genetic connection with contemporaneous volcanism. The control exerted by the volcanic succession (e.g., rock type, architecture and facies) on the nature and style of the ore and alteration (e.g., subsea-floor replacement vs. exhalative, or d...
Article
Full-text available
The ultramafic Eocene Missouri River Breaks volcanic field (MRBVF, Montana, USA) includes over 50 diatremes emplaced in a mostly soft substrate. The current erosion level is 1.3–1.5 km below the pre-eruptive surface, exposing the deep part of the diatreme structures and some dikes. Five representative diatremes are described here; they are 200-375...
Article
Full-text available
Portable X-ray fluorescence (pXRF) analysers are increasingly popular tools for geoscientific applications, including mineral exploration. One promising application, illustrated in the companion paper, is to obtain high-spatial resolution down-hole geochemical profiles using pXRF on unprepared exploration drill-cores. However, the precision and acc...
Article
Full-text available
A new geoscientific application of portable XRF (pXRF) analysers is the acquisition of high-spatial resolution down-hole geochemical profiles obtained in-situ on exploration drill-cores. One advantage of such profiles over traditional laboratory geochemistry, apart from the non-destructive aspect of pXRF, is that they are obtained quickly, in the f...
Conference Paper
The Lalor auriferous VMS deposit is located in the ca. 1.85 Ga Snow Lake arc assemblage that is part of the Paleopropterozoic Flin Flon greenstone belt. The Snow Lake camp is host to numerous past producing Cu-Zn, Zn-Cu and Au-Zn-Cu VMS deposits and one orogenic Au deposit. Lalor is the largest deposit of the Snow Lake camp and also the richest in...
Article
Basaltic maar-diatreme volcanoes, which have craters cut into pre-eruption landscapes (maars) underlain by downward-tapering bodies of fragmental material commonly cut by hypabyssal intrusions (diatremes), are produced by multiple subsurface phreatomagmatic explosions. Although many maar-diatremes have been studied, the link between explosion dynam...
Article
The Matagami mining camp in the northern Abitibi greenstone belt of Canada contains 19 known Archean volcanogenic massive sulfide (VMS) deposits, eleven of which have collectively produced 46.5 Mt of zinc-rich ore to date. The VMS deposits occur in three NW-SE to WNW-ESE oriented trends called the North Flank, the South Flank, and the West Camp whi...
Article
Full-text available
An innovative approach to enhance volcanogenic massive sulfide (VMS) exploration in regions outside of mining camps is to first use physical volcanology with litho- and chemo-stratigraphy to establish the location of effusive centers in the volcanic units and use pyrite geochemistry in sulfide-bearing stratified intervals with whole-rock geochemist...
Article
The 2704 to 2695 Ma Blake River Group in the southern Abitibi greenstone belt comprises a well preserved submarine volcanic sequence that hosts a large number of VMS and important Au-rich VMS deposits, including the world-class Horne and LaRonde-Penna deposits. Establishing precise chronostratigraphic control on the VMS deposits within the Blake Ri...
Technical Report
Full-text available
The Lalor volcanogenic massive-sulphide deposit is the largest deposit in the Snow Lake mining camp and is also the richest in terms of total contained Au. The deposit is affected by polyphase deformation that has strongly influenced the geometry of the ore zones and the distribution of metals. Underground mapping has been completed at several sele...
Technical Report
Full-text available
Lalor is a recently discovered Au-rich Zn-Cu volcanogenic massive sulphide (VMS) deposit. It is located in the Paleoproterozoic Snow Lake arc assemblage, host to numerous past producing Cu-Zn and Zn-Cu VMS deposits. With an estimated tonnage of 25 Mt of ore (reserves + resources) including 73 t Au, Lalor is the largest VMS deposit in the Snow Lake...
Article
Full-text available
Volcanogenic massive sulphide (VMS) deposits and seafloor massive sulphide (SMS) deposits have a spatial and genetic connection with contemporaneous volcanism. The control exerted by the volcanic succession (e. g. rock type, architecture and facies) on the nature and style of the ore and alteration (e. g. subsea-floor replacement vs. exhalative, or...
Conference Paper
Full-text available
Ballistics - bomb-sized pyroclasts that travel from volcanic source to final emplacement position along ballistic trajectories - represent a prime source of volcanic hazard, but their emplacement range, size, and density is useful to inverse model key eruption parameters related to their initial ejection velocity. Models and theory, however, have s...
Conference Paper
Detailed analysis of volcanic craters and ballistic deposits can provide insight into eruption dynamics and evolution. As fully exposed craters and associated unmodified deposits are rarely preserved, the dynamics involved can only be inferred. Large-scale blast experiments conducted at the University at Buffalo Geohazards Field Station produced de...
Conference Paper
In an ongoing effort to understand the relevant processes behind the formation of volcanic crater-, maar-, and diatreme structures, experiments producing craters with radii exceeding one meter were conducted at University at Buffalos Geohazards Field Station. A chemical explosive was used as energy source for the tests, and detonated in prepared te...
Conference Paper
The Lalor auriferous Zn-Cu-Ag VMS is the largest deposit of the Snow Lake camp with reserves of 15.1 Mt at 7.2% Zn, 0.6% Cu, 1.9 g/t Au and 23.3 g/t Ag and resources of 12 Mt at 2.6% Zn, 0.9% Cu, 4.0 g/t Au and 27.8 g/t Ag. The deposit consists of highly-strained, stacked massive to semi-massive Zn-Cu±Au, Au-Cu and Au zones that are hosted in inten...
Article
Full-text available
Diamond drilling typically constitutes a major part of costs in advanced mineral exploration programs. This generates thousands of meters of rock cores during major exploration campaigns, but the cores are not currently utilized to their full potential. They could supply three-dimensional information on physical properties, geochemistry and mineral...
Article
Full-text available
Maar–diatreme eruptions are hazardous to people and infrastructure, and are also linked to the formation of the kimberlitic variety of diatremes, which is important economically. Processes occurring in the subsurface diatreme and their relation to surface eruptions are not yet well understood. We conducted field-scale experiments using analog mater...
Conference Paper
Lalor is a recently discovered Au-Zn-rich volcanogenic massive sulphide (VMS) deposit. It is located in the Paleoproterozoic Snow Lake arc assemblage, host to numerous past producing Cu-Zn and Zn-Cu VMS deposits. Lalor is the largest deposit of the Snow Lake camp and also the richest in gold with reserves of 14.4 Mt at 1.86 g/t Au, 24 g/t Ag, 0.6...
Article
Full-text available
Most volcanic eruptions occur in craters formed by previous activity. The presence of a crater implies specific confinement geometries, variably filled by loose fragmental deposits, which are expected to exert a strong, yet poorly studied, control on the violent gas expansion that drives the eruption. Here we analyze patterns of ejection from burie...
Article
Full-text available
Vesicles within juvenile fragments in mafic pyroclastic deposits contain important information about the state of the magma at the time of fragmentation. There have been few vesicle studies of juvenile pyroclasts from mafic phreatomagmatic deposits, however, and none we can find from maar–diatreme volcanoes. In this paper we document the vesiculari...
Article
Craters at many volcanoes, including most maars, are formed by multiple subsurface explosions. Experiments compared the crater formed by a single large, buried explosion, with craters formed by multiple explosions with the same cumulative energy. Explosive charges were detonated in pads composed of layered aggregates, in three configurations: (1) a...
Article
Full-text available
In the Archean Blake River Group, mafic to intermediate fragmental units have controversially been proposed to have formed during the collapse of a giant submarine caldera. This paper describes and interprets these rocks, summarizing their physical characteristics, inferred origins, age relationships, and geochemical signatures. The widespread Stad...
Article
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Maar-diatreme volcanoes are produced by explosive eruptions that cut deeply into the country rock. A maar is the crater cut into the ground and surrounded by an ejecta ring, while the diatreme structure continues downward and encloses diatreme and root zone deposits. Here we attempt an evenhanded review of maar-diatreme volcanology that extends fro...
Article
Full-text available
The morphologic parameters, pyroclastic deposits and evolution of maar–diatreme volcanoes are affected by the type of environment in which they are emplaced. End-member cases are a hard substrate (rocks) and a soft substrate (unconsolidated volcaniclastic or sedimentary deposits). In this paper, we present an example of a volcanic complex emplaced...
Article
Full-text available
The Archean Blake River Group (BRG) of Ontario and Quebec is dominated by submarine mafic to intermediate lavas, with more restricted felsic volcanic rocks. Given the good quality of outcrop, and high level of preservation of some BRG rocks, the mafic to intermediate lavas were used in the 1970s and 1980s to better understand the evolution of massi...
Article
Full-text available
Large igneous provinces (LIPs) form in both oceanic and continental settings by the emplacement and eruption of voluminous magmas ranging from basalt to rhyolite in composition. Continental flood basalt provinces are the best studied LIPs and consist of crustal intrusive systems, extensive flood lavas and ignimbrites, and mafic volcaniclastic depos...