DOCSLIB.ORG

Potential Effects of Hydrothermal Circulation and Magmatism on Heatflow at Hotspot Swells

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Potential Effects of Hydrothermal Circulation and Magmatism on Heatflow at Hotspot Swells The Geological Society of America Special Paper 430 2007 Potential effects of hydrothermal circulation and magmatism on heatflow at hotspot swells Carol A. Stein* Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7059, USA Richard P. Von Herzen* Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Clark 244B, MS#22, Woods Hole, Massachusetts 02543, USA, and Department of Earth Sciences, University of California at Santa Cruz, Earth and Marine Science Building, Santa Cruz, California 95064-1077, USA ABSTRACT The lack of high heatflow values at hotspots has been interpreted as showing that the mechanism forming the associated swells is not reheating of the lower half of oceanic lithosphere. Alternatively, it has recently been proposed that the hotspot sur- face heatflow signature is obscured by fluid circulation. We re-examine closely spaced heatflow measurements near the Hawaii, Réunion, Crozet, Cape Verde, and Bermuda hotspots. We conclude that hydrothermal circulation may redistribute heat near the swell axes, but it does not mask a large and spatially broad heatflow anomaly. There may, however, be heatflow perturbations associated with the cooling of igneous intru- sions emplaced during hotspot formation. Although such effects may raise heatflow at a few sites, the small heatflow anomalies indicate that the mechanisms producing hotspots do not significantly perturb the thermal state of the lithosphere. Keywords: heatflow, swell, hotspot, mantle plume INTRODUCTION anomalies at hotspots (e.g., Crough, 1978). A consequence of this mechanism is unusually high surface heatflow, which After the recognition that hotspots, regions of excess vol- should be measurable by established methodologies. The first canism and higher elevation compared to surrounding areas, re- detailed study of the Hawaiian hotspot found high mean heat- sult from the rise of material through the mantle to the Earth’s flow (Von Herzen et al., 1982), but subsequent studies showed surface beneath both oceans and continents, marine geothermal that the anomaly was overestimated because the reference measurements were among the first geophysical techniques model predicted significantly lower heatflow than observed in used to assess their nature. Initially it was proposed that signif- unperturbed older lithosphere (Von Herzen et al., 1989; Stein icant reheating of the bottom half of the lithosphere over a dis- and Stein, 1993). The conclusion was that lithospheric reheat- tance of ~300 km in diameter was required to match the depth ing is not a major factor in hotspot formation. Thus, possible *E-mails: Stein, [email protected]; Von Herzen, [email protected]. Stein, C.A., and Von Herzen, R.P., 2007, Potential effects of hydrothermal circulation and magmatism on heatflow at hotspot swells, in Foulger, G.R., and Jurdy, D.M., eds., Plates, plumes, and planetary processes: Geological Society of America Special Paper 430, p. 261–274, doi: 10.1130/2007.2430(13). For permission to copy, contact [email protected]. ©2007 The Geological Society of America. All rights reserved. 261 262 Stein and Von Herzen mechanisms producing the swells must be consistent with small on the answer to this question, different mechanisms have been or essentially zero heatflow anomalies, such as those expected proposed for hotspot formation. for dynamic models (e.g., Ribe and Christensen, 1994). Many mechanisms have been suggested to explain hotspot However, it has been recently proposed (Harris et al., formation. An important observation to model is the anom- 2000a,b) that hydrothermal circulation may obscure the signal alously shallow bathymetry and its subsequent subsidence (e.g., from the processes forming hotspots. Harris et al. (2000a, DeLaughter et al., 2005). For example, the reheating model re- p. 21,368) suggested that “fluid flow has the potential to obscure quires significant upwelling of mantle material that rapidly thins basal heatflow patterns associated with the Hawaiian hot spot,” the bottom half of the overlying plate (Crough, 1978, 1983). For which would “not bode well for capturing the form and magni- the dynamic plume model that incorporates a large viscosity tude of this signature.” Most hydrothermal circulation occurs in contrast between the plume and overlying lithosphere, most re- young oceanic crust (0 to ca. 65 Ma), resulting in lower mea- heating is at the base of the lithosphere (e.g., Liu and Chase, sured heatflow compared to conductive cooling models of the 1989; Ribe and Christensen, 1994). The compositional buoyancy lithosphere. Heatflow transferred by hydrothermal circulation model predicts shallower depths from relatively low-density in older oceanic lithosphere is thought to be much less (e.g., magmas emplaced either within the lithosphere or near its base Stein and Stein, 1994; Von Herzen, 2004). However, as sug- (e.g., Robinson, 1988; Sleep, 1994; Phipps Morgan et al., 1995). gested above, if the overall rough basement and islands and Different amounts of reheating and excess heatflow with time seamounts associated with hotspots cause fluid flow to occur since hotspot formation are expected from these different mech- both in the igneous basement and perhaps in the relatively per- anisms. Hence, heatflow data may help to discriminate among meable volcaniclastic sediments, then “capturing the maximum them. basal heat flux may be confounded by fluid flow” (Harris et al., For the Hawaiian chain, on the relatively fast-moving Pa- 2000a, p. 21,368). Evidence on the magnitude and extent of cific plate, matching the observed uplift and subsequent subsi- hydrothermal heat transfer may be provided by the detailed dence by the reheating mechanism requires that the bottom third heatflow at the five hotspots on crust older than ~65 Ma. to half of the oceanic lithosphere is rapidly reheated to as- In this article, we first examine heatflow anomalies near thenospheric temperatures over a zone 300 km wide centered on these hotspots. The anomalies are computed relative to the the axis (Von Herzen et al., 1982). At the time reheating begins, Global Depth and Heatflow reference model (Stein and Stein, the surface heatflow anomaly should be zero, but as the plate 1992) and with crustal ages from Mueller et al. (1997). Second, moves away from the upwelling, the heating of the lower litho- we examine which sites may be affected by hydrothermal cir- sphere propagates upward by conduction. The predicted anom- culation and thus mask higher heatflow. Last, we consider heat- aly gradually increases to a maximum of ~25 mW m–2 ~15–20 flow perturbations associated with the cooling of igneous struc- m.y. after reheating and then gradually decreases. The heatflow tures that result from the hotspot processes, including the igneous anomaly should be a maximum at the axis of the chain and de- material emplaced on the surface of pre-existing oceanic crust, crease to zero over ~600 km normal to the axis (Fig. 1A). and intruded sills at subcrustal depths. Although anomalously high heatflow was initially reported for the Hawaiian chain (Von Herzen et al., 1982), consistent with ESTIMATED HEATFLOW significant lithospheric reheating, subsequent data and analysis ANOMALIES FROM HOTSPOTS (Von Herzen et al., 1989; Stein and Stein, 1993) showed that the expected Gaussian distribution of anomalous heat flux orthogo- Although the depth in the Earth from which hotspots orig- nal to the axis did not exist, and many of the apparent anomalies inate is still debated (e.g., Sleep, 2003; Anderson, 2005; Foul- along axis result from comparing the data to reference thermal ger, this volume; Garnero et al., this volume), a geophysical models that underestimate heatflow elsewhere. Thus, the impli- challenge is to separate the effects of mechanisms forming cation is that heatflow data do not support swell formation by hotspots from shallower lithospheric processes, including the extensive lithospheric heating. “normal” lithospheric cooling as the plate ages. Lithospheric in- The small heatflow anomaly and absence of the pattern ex- teractions with the upward flow of magma, the absolute veloc- pected for lithospheric reheating at Hawaii and other marine ity of the plate, and near-surface physical processes (including hotspots (Réunion [Bonneville et al., 1997], Bermuda [Detrick excess volcanism and hydrothermal circulation) complicate the et al., 1986], Cape Verde [Courtney and White, 1986], and Crozet task of understanding the deeper mantle processes leading to the [Courtney and Recq, 1986]) imply that uplift may result from formation of hotspots. Also, because heat is largely transferred the dynamic effects of rising plumes. Their thermal effects are by conduction through the lithosphere, excess heat loss associ- concentrated at the base of the lithosphere and hence would raise ated with hotspot formation at a given location may occur long surface heatflow at most slightly, given that tens of millions after the hotspot upwelling has ceased. Although hotspots are of years are required for the conduction of heat to the surface. associated with anomalously shallow bathymetry, it is unclear For example, Ribe and Christensen (1994) predicted heatflow whether their surface heatflow is anomalously high. Depending anomalies for Hawaii of less than 1 mW m–2 (Fig. 1B). The heat- Potential effects of hydrothermal circulation and magmatism on heatflow 263 Figure 1. Predicted heatflow anomalies from reheating and dynamic plume mod- els. (A) The reheating model predicts heatflow anomalies up to ~25 mW m–2 (Von Herzen et al., 1982) in contrast to (B) a dynamic plume model of less than 1 mW m–2 (Ribe and Christensen, 1994). The location of heatflow measurements for Hawaii from Von Herzen et al. (1982, 1989) and Harris et al. (2000a) are shown in panel A. In panel B, the predicted sur- face heatflow from an upwelling plume (location indicated by the solid semicir- cle) beneath a moving plate is shown for up to 2400 km downstream of where the plume has passed (horizontal axis) and for up to 1600 km perpendicular (verti- cal axis) from the path of the plume.
Load more

Recommended publications
  • Hydrothermal Circulation Within the Endeavour Segment; Juan De Fuca Ridge
    Hydrothermal Circulation within the Endeavour Segment; Juan de Fuca Ridge H. Paul Johnson1, Maurice A. Tivey2, Tor A. Bjorklund1, and Marie S. Salmi1 1School of Oceanography, University of Washington, Seattle, WA 98195-7940 2Department of Geology and Geophysics Woods Hole Oceanographic Institution Woods Hole, MA 02543 Correspondence should be addressed to HPJ, [email protected] 206-543-8474 Hydrothermal Circulation within the Endeavour Segment; Juan de Fuca Ridge Abstract Areas of the seafloor at mid-ocean ridges where hydrothermal vents discharge are easily recognized by the dramatic biological, physical and chemical processes that characterize such sites. Locations where seawater flows into the seafloor to recharge hydrothermal cells within the crustal reservoir are by contrast almost invisible, but can be indirectly identified by a systematic grid of conductive heat flow measurements. An array of conductive heat flow stations in the Endeavour axial valley of the Juan de Fuca Ridge has identified recharge zones that appear to represent a nested system of fluid circulation paths. At the scale of an axial rift valley, conductive heat flow data indicate a general cross-valley fluid flow, where seawater enters the shallow sub-surface crustal reservoir at the eastern wall of the Endeavour axial valley and undergoes a kilometer of horizontal transit beneath the valley floor, finally exiting as warm hydrothermal fluid discharge on the western valley bounding wall. Recharge zones also have been identified as located within an annular ring of very cold seafloor around the large Main Endeavour Hydrothermal Field, with seawater inflow occurring within faults that surround the fluid discharge sites.
    [Show full text]
  • Three-Dimensional Models of Hydrothermal Circulation Through a Seamount Network on Fast-Spreading Crust ∗ Rachel M
    Earth and Planetary Science Letters 501 (2018) 138–151 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Three-dimensional models of hydrothermal circulation through a seamount network on fast-spreading crust ∗ Rachel M. Lauer a,b,c, , Andrew T. Fisher b,c, Dustin M. Winslow b,c,d a Department of Geoscience, University of Calgary, Calgary, Alberta, Canada b Earth and Planetary Sciences Department, University of California, Santa Cruz, 95064, USA c Center for Dark Energy Biosphere Investigations, University of California, Santa Cruz, 95064, USA d GrowthIntel, 25-27 Horsell Road, London N5 1XL, UK a r t i c l e i n f o a b s t r a c t Article history: We present results from three-dimensional, transient, fully coupled simulations of fluid and heat Received 25 February 2018 transport on a ridge flank in fast-spread ocean crust. The simulations quantify relationships between rates Received in revised form 17 July 2018 of fluid flow, the extent of advective heat extraction, the geometry of crustal aquifers and outcrops, and Accepted 14 August 2018 crustal hydrologic parameters, with the goal of simulating conditions similar to those seen on 18–24 M.y. Available online xxxx old seafloor of the Cocos plate, offshore Costa Rica. Extensive surveys of this region documented a Editor: M. Bickle 2 ∼14,500 km area of the seafloor with heat flux values that are 10–35% of those predicted from Keywords: conductive cooling models, and identified basement outcrops that serve as pathways for hydrothermal hydrothermal circulation circulation via recharge of bottom water and discharge of cool hydrothermal fluid.
    [Show full text]
  • 27. Chinook Trough Rifting and Hydrothermal Deposition at Sites 885 and 8861
    Rea, D.K., Basov, I.A., Scholl, D.W., and Allan, J.F. (Eds.), 1995 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 145 27. CHINOOK TROUGH RIFTING AND HYDROTHERMAL DEPOSITION AT SITES 885 AND 8861 Gerald R. Dickens2 and Robert M. Owen2 ABSTRACT The Chinook Trough is a pronounced deep located in the central North Pacific Ocean that spans approximately 1500 km in a northeast-southwest direction. Geophysical and geomorphological considerations suggest that this feature is the southern litho- spheric scar marking initiation of Late Cretaceous north-south rifting within the ancient Farallon Plate. If this hypothesis is correct, then, by analogy to other active and passive mid-ocean rift zones, Late Cretaceous sediment deposited immediately south of the Chinook Trough should contain significant amounts of hydrothermal material deposited in association with the intraplate rifting event. Because the proposed tectonic origin for the Chinook Trough places seafloor south of the eastern end of the trough beneath the Cretaceous calcite compensation depth (CCD), expected hydrothermal components deposited during the Late Cretaceous at these locations also should lack carbonate dilution. Ocean Drilling Program Sites 885 and 886 were drilled approximately 60 km south of the northeast section of the Chinook Trough. High-resolution chemical and mineralogical analyses demonstrate that sediment deposited after 75-81 Ma at these sites contains an extensive record of hydrothermal deposition without associated carbonate. Various proxy indicators
    [Show full text]
  • Seafloor Hydrothermal Activity Around a Large Non-Transform
    Journal of Marine Science and Engineering Article Seafloor Hydrothermal Activity around a Large Non-Transform Discontinuity along Ultraslow-Spreading Southwest Indian Ridge (48.1–48.7◦ E) Dong Chen 1,2, Chunhui Tao 2,3,*, Yuan Wang 2, Sheng Chen 4, Jin Liang 2, Shili Liao 2 and Teng Ding 1 1 Institute of Marine Geology, College of Oceanography, Hohai University, Nanjing 210098, China; [email protected] (D.C.); [email protected] (T.D.) 2 Key Laboratory of Submarine Geosciences, SOA & Second Institute of Oceanography, MNR, Hangzhou 310012, China; [email protected] (Y.W.); [email protected] (J.L.); [email protected] (S.L.) 3 School of Oceanography, Shanghai Jiao Tong University, Shanghai 200240, China 4 Ocean Technology and Equipment Research Center, School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China; [email protected] * Correspondence: [email protected] Abstract: Non-transform discontinuity (NTD) is one category of tectonic units along slow- and ultraslow-spreading ridges. Some NTD-related hydrothermal fields that may reflect different driving mechanisms have been documented along slow-spreading ridges, but the discrete survey strategy makes it hard to evaluate the incidence of hydrothermal activity. On ultraslow-spreading ridges, fewer NTD-related hydrothermal activities were reported. Factors contributing to the occurrence of hydrothermal activities at NTDs and whether they could be potential targets for hydrothermal explo- Citation: Chen, D.; Tao, C.; Wang, Y.; Chen, S.; Liang, J.; Liao, S.; Ding, T. ration are poorly known. Combining turbidity and oxidation reduction potential (ORP) sensors with Seafloor Hydrothermal Activity a near-bottom camera, Chinese Dayang cruises from 2014 to 2018 have conducted systematic towed around a Large Non-Transform surveys for hydrothermal activity around a large NTD along the ultraslow-spreading Southwest ◦ Discontinuity along Indian Ridge (SWIR, 48.1–48.7 E).
    [Show full text]
  • Complex Subsurface Hydrothermal Fluid Mixing at a Submarine Arc Volcano Supports Distinct and Highly Diverse Microbial Communities
    Complex subsurface hydrothermal fluid mixing at a submarine arc volcano supports distinct and highly diverse microbial communities Anna-Louise Reysenbacha,1,2, Emily St. Johna,2, Jennifer Meneghina, Gilberto E. Floresb, Mircea Podarc, Nina Dombrowskid, Anja Spangd,e, Stephane L’Haridonf, Susan E. Humphrisg, Cornel E. J. de Rondeh, Fabio Caratori Tontinih, Maurice Tiveyg, Valerie K. Stuckeri, Lucy C. Stewarth,j, Alexander Diehlk,l, and Wolfgang Bachk,l aCenter for Life in Extreme Environments, Biology Department, Portland State University, Portland, OR 97201; bDepartment of Biology, California State University, Northridge, CA 91330; cBiosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831; dRoyal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, NL-1790 AB Den Burg, The Netherlands; eDepartment of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden; fCNRS, Institut Français de Recherche pour l’Exploitation de la Mer, Laboratoire de Microbiologie des Environnements Extrêmes, Université de Bretagne Occidentale, F-29280 Plouzané, France; gDepartment of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; hDepartment of Earth Systems and Resources, GNS Science, Avalon, Lower Hutt 5010, New Zealand; iLaboratories and Collections, GNS Science, Avalon, Lower Hutt 5010, New Zealand; jToha Science, Wellington 6011, New Zealand; kFaculty of Geosciences, University of Bremen, 28359 Bremen, Germany; and lMARUM - Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany Edited by Edward F. DeLong, University of Hawaii at Manoa, Honolulu, HI, and approved November 3, 2020 (received for review September 10, 2020) Hydrothermally active submarine volcanoes are mineral-rich bio- seawater circulation through oceanic crust.
    [Show full text]
  • On the Great Plume Debate of Geophysical Fluid Dynamics at Research School of Earth Sciences, the Australian National University
    NEWS & VIEWS Chinese Science Bulletin 2005 Vol. 50 No. 15 1537—1540 2 About the authors Geoff F. Davies is currently a Senior Research Fellow On the great plume debate of Geophysical Fluid Dynamics at Research School of Earth Sciences, The Australian National University. He Yaoling Niu received a B.Sc. with honours (1966) and an M.Sc. (1968) Department of Earth Sciences, Durham University, Durham DH1 3LE, UK from Monash University in Australia, and a Ph.D. from (email: [email protected]) California Institute of Technology (Caltech) in the USA DOI: 10.1360/982005-1156 (1973). His PhD thesis dealt with mineral physics titled ‘Elasticity of solids at high temperatures and pressures: 1 Introductory note Theory, measurement and geophysical application’. He held positions at Harvard University, University of Roch- Geological processes are ultimately consequences of ester and Washington University in the USA before he Earth’s thermal evolution. Plate tectonic theory, which took his present post in 1983. He is an expert on mineral explains geological phenomena along plate boundaries, physics, very knowledgeable on geology and geochemis- elegantly illustrates this concept. For example, the origin try with deep interest in dynamics and evolution of the of oceanic plates at ocean ridges, the movement and earth's mantle: plate tectonics, mantle convection and growth of these plates, and their ultimate consumption chemical evolution. He is also interested in and researches back into the Earth’s deep interior through subduction on crust-mantle interaction, early Earth process and other zones provide an efficient mechanism to cool the earth’s planets.
    [Show full text]
  • Chinese Science Bulletin Debate
    Chinese Science Bulletin www.scichina.com 50 vol. No 15 1537-1672 August 2005 In this issue: Great Plume Debate! A case for mantle plumes (Geoffrey F. Davies, p. 1541-1554) Mantle plumes: Why the current skepticism? (Gillian R. Foulger, p. 1555-1560) preceded by News & Views (Yaoling Niu, p. 1537-1540) NEWS & VIEWS Chinese Science Bulletin 2005 Vol. 50 No. 15 1537—1540 2 About the authors Geoff F. Davies is currently a Senior Research Fellow On the great plume debate of Geophysical Fluid Dynamics at Research School of Earth Sciences, The Australian National University. He Yaoling Niu received a B.Sc. with honours (1966) and an M.Sc. (1968) Department of Earth Sciences, Durham University, Durham DH1 3LE, UK from Monash University in Australia, and a Ph.D. from (email: [email protected]) California Institute of Technology (Caltech) in the USA DOI: 10.1360/982005-1156 (1973). His PhD thesis dealt with mineral physics titled ‘Elasticity of solids at high temperatures and pressures: 1 Introductory note Theory, measurement and geophysical application’. He held positions at Harvard University, University of Roch- Geological processes are ultimately consequences of ester and Washington University in the USA before he Earth’s thermal evolution. Plate tectonic theory, which took his present post in 1983. He is an expert on mineral explains geological phenomena along plate boundaries, physics, very knowledgeable on geology and geochemis- elegantly illustrates this concept. For example, the origin try with deep interest in dynamics and evolution of the of oceanic plates at ocean ridges, the movement and earth's mantle: plate tectonics, mantle convection and growth of these plates, and their ultimate consumption chemical evolution.
    [Show full text]
  • DON ANDERSON Themes Developed Across Several Decades
    Don L. Anderson 1933–2014 A Biographical Memoir by Thorne Lay ©2016 National Academy of Sciences. Any opinions expressed in this memoir are those of the author and do not necessarily reflect the views of the National Academy of Sciences. DON LYNN ANDERSON March 5, 1933–December 2, 2014 Elected to the NAS, 1982 Don L. Anderson, the Eleanor and John R. McMillan Professor of Geophysics at the California Institute of Tech- nology, was a geophysicist who made numerous seminal contributions to our understanding of Earth’s origin, composition, structure and evolution. He pioneered applications of seismic anisotropy for global surface waves, contributed to discovering the seismic velocity discontinuities in the mantle’s transition zone and initi- ated their mineralogical interpretation, established deep insights into seismic attenuation, co-authored the most widely used reference Earth structure model, helped to establish the field of global tomography, and re-opened inquiry into the nature of hotspot volcanism and mantle stratification. He contributed to initiatives that upgraded By Thorne Lay global and regional seismic instrumentation. He served as Director of the Caltech Seismological Laboratory for 22 years, overseeing a prolific scientific environment, distilling many advances into his masterpiece book Theory of the Earth. His enthusiasm for debate and his phenomenal editorial efforts raised the scientific standard of students and colleagues alike. Don was a geophysicist of tremendous breadth, publishing about 325 peer-reviewed research papers between 1958 and 2014 in seismology, mineral physics, planetary science, tectonophysics, petrology and geochemistry. He had a remarkable familiarity with the literature across all these disciplines, keeping reprints sorted into a multitude of three-ring binders that he could access in an instant, uniquely positioning him to undertake the writing of his ambitious book, The Theory of the Earth, published in 1989.
    [Show full text]
  • Are There Significant Hydrothermal Resources in the U.S
    PROCEEDINGS. 'Twentieth Workshop on Geothermal Reselvolr Englneerlng Stanford Univenlty. Stanford, Califomla, January 2426 1995 scP-?RR-Iso ARE THERE SIGNIFICANT HYDROTHERMAL RESOURCES IN THE U.S. PART OF THE CASCADE RANGE? L.J. Patrick Muffler' and Marianne Guffanti2 US Geological Survey, MS 910, Menlo Park, CA 94025 2US Geological Survey, MS 922, Reston, VA 22092 ABSTRACT INTRODUCTION The Cascade Range is a geothermal dichotomy. On This paper presents preliminary conclusions from a the one hand, it is an active volcanic arc above a multi-year effort of the U.S. Geological Survey to subducting plate and is demonstrably an area of high evaluate the geothermal potential of the Cascade heat flow. On the other hand, the distribution of Range. A detailed assessment will be published as a hydrothermal manifestations compared to other Bulletin of the U.S. Geological Survey (Muffler and volcanic arcs is sparse, and the hydrothermal outflow Guffanti, in preparation). Here we draw heavily on a calculated from stream chemistry is low. manuscript (Guffanti and Muffler, 1995) submitted to the May 1995 World Geothermal Congress in Several large estimates of undiscovered geothermal Florence, Italy, as well as several recent publications resources in the U.S. part of the Cascade Range of our USGS colleagues, particularly Ingebritsen prepared in the 1970s and early 1980s were based etal. (1989, 1992, 1994), Mariner etal. (1990), and fundamentally on two models of the upper crust. One Blakely (1994). model assumed that large, partly molten, intrusive bodies exist in the upper 10 km beneath major volcanic centers and serve as the thermal engines driving overlying hydrothermal systems.
    [Show full text]
  • The Hawaiian SWELL Pilot Experiment—Evidence for Lithosphere Rejuvenation from Ocean Bottom Surface Wave Data
    The Geological Society of America Special Paper 430 2007 The Hawaiian SWELL pilot experiment—Evidence for lithosphere rejuvenation from ocean bottom surface wave data Gabi Laske Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0225, USA Jason Phipps Morgan Department of Earth & Atmospheric Sciences, Snee Hall, Cornell University, Ithaca, New York, 14853-1504 John A. Orcutt Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0225, USA ABSTRACT During the roughly year-long Seismic Wave Exploration in the Lower Lithosphere (SWELL) pilot experiment in 1997/1998, eight ocean bottom instruments deployed to the southwest of the Hawaiian Islands recorded teleseismic Rayleigh waves with peri- ods between 15 and 70 s. Such data are capable of resolving structural variations in the oceanic lithosphere and upper asthenosphere and therefore help understand the mechanism that supports the Hawaiian Swell relief. The pilot experiment was a tech- nical as well as a scientific feasibility study and consisted of a hexagonal array of Scripps Low-Cost Hardware for Earth Applications and Physical Oceanography (L-CHEAPO) instruments using differential pressure sensors. The analysis of eighty- four earthquakes provided numerous high-precision phase velocity curves over an un- precedentedly wide period range. We find a rather uniform (unaltered) lid at the top of the lithosphere that is underlain by a strongly heterogeneous lower lithosphere and upper asthenosphere. Strong slow anomalies appear within ~300 km of the island chain and indicate that the lithosphere has most likely been altered by the same process that causes the Hawaiian volcanism.
    [Show full text]
  • 4. Regional Environment
    4. Regional Environment By Klaus J. Schulz 4 of 21 Volcanogenic Massive Sulfide Occurrence Model Scientific Investigations Report 2010–5070–C U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Schulz, K.J., 2012, Regional environment in volcanogenic massive sulfide occurrence model: U.S. Geological Survey Scientific Investigations Report 2010–5070 –C, chap. 4, 24 p. 35 Contents Geotectonic Environment ...........................................................................................................................37 Mid-Ocean Ridges and Mature Back-Arc Basins (Mafic-Ultramafic Lithologic Association) .........................................................................................................37
    [Show full text]
  • Heat Flow and Bending-Related Faulting at Subduction Trenches: Case Studies Offshore of Nicaragua and Central Chile
    Earth and Planetary Science Letters 236 (2005) 238–248 www.elsevier.com/locate/epsl Heat flow and bending-related faulting at subduction trenches: Case studies offshore of Nicaragua and Central Chile Ingo Grevemeyera,*, Norbert Kaulb, Juan L. Diaz-Naveasc, Heinrich W. Villingerb, Cesar R. Raneroa, Christian Reichertd aIFM-GEOMAR, Leibniz Institute for Marine Sciences, and SFB 574, Wischhofstrabe 1-3, 24148 Kiel, Germany bDepartment of Earth Sciences, University of Bremen, Klagenfurter Strabe, 28359 Bremen, Germany cSchool of Marine Sciences, Catholic University of Valparaı´so, Av. Altmirano 1480, Valparaı´so, Chile dFederal Institute for Geosciences and Resources, Stilleweg 2, 30655 Hanover, Germany Received 19 July 2004; received in revised form 10 March 2005; accepted 11 April 2005 Available online 1 July 2005 Editor: V. Courtillot Abstract Detailed heat flow surveys on the oceanic trench slope offshore Nicaragua and Central Chile indicate heat flow values lower than the expected conductive lithospheric heat loss and lower than the global mean for crust of that age. Both areas are characterised by pervasive normal faults exposing basement in a setting affected by bending-related faulting due to plate subduction. The low heat flow is interpreted to indicate increased hydrothermal circulation by the reactivation and new creation of faults prior to subduction. A previous global approach [1] [Stein C.A., Heat flow and flexure at subduction zones, Geophys. Res. Lett. 30 (2003) doi:10.1029/2003GL018478] failed to detect similar features in the global but sparse data set. Detailed inspection of the global data set suggests that the thickness of the sedimentary blanket on the incoming plate is an important factor controlling the local hydrogeological regime.
    [Show full text]