Physics
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003trgeo...2..471v&link_type=abstract
Treatise on Geochemistry, Volume 2. Editor: Richard W. Carlson. Executive Editors: Heinrich D. Holland and Karl K. Turekian. pp
Physics
2
Scientific paper
The observed geochemical diversity of mid-oceanic ridge basalts (MORBs) and ocean island basalts (OIBs) is generally attributed to the existence of large-scale and long-term chemical heterogeneity in the Earth's silicate mantle (see Chapter 2.03). Yet, it is far from clear how this heterogeneity is generated and how it is maintained in the convecting mantle. Quantitative mixing studies indicate that the present-day Earth is convecting vigorously enough to erase significant initial heterogeneity well within the age of the Earth. This suggests that some form of layering, or barrier against convective mixing is required to explain the geochemical observations. The most basic form of layering is that of the "classical" two-layer mantle, where a depleted and well-mixed upper mantle is separated by the seismically distinct 670 km boundary from a poorly mixed and enriched lower mantle. The MORBs originate from melting of the upper mantle, whereas OIBs derive from melting of material that is brought up from the lower mantle by plumes. This model has worked well to explain a large number of observations regarding noble gas and trace element concentrations and the distribution of mantle heat sources. However, in recent years this model has come under siege. Geophysical and geodynamical observations indicate that significant mass exchange occurs through the Earth's transition zone. In addition, various geochemical observations suggest an important role for oceanic crust recycling in the plume source and demonstrate the lack of preservation of primitive mantle. The recent widespread acceptance of these fundamental problems of the classical layered mantle model has led the proposition of various alternatives such as the presence of layering below 670 km depth, or the preservation of heterogeneity in highly viscous regions in the Earth's mantle. These models appear to be able to explain one or more features better than the classical model, but often cause new conflicts with existing geochemical or geophysical observations. In addition, it is not always clear that these new conceptual models are physically realistic. With the advent of large-scale computing, geodynamical modeling has become a particularly useful tool in this arena. Using the fundamental laws of the conservation of mass, energy, and momentum, models of mantle convection can be created that allow for quantitative tests of these conceptual models. Modeling also allows for a better understanding of the physics that governs mantle flow, mantle mixing, and the distribution of chemical heterogeneity in planetary interiors.This chapter will focus on the use of mantle convection modeling in the development of our understanding of the chemical evolution of the Earth by providing a short review of the main observations, a discussion of the physical approaches to characterize mantle mixing, and an overview of the historical and current modeling approaches to the formation, preservation, and destruction of chemical heterogeneity. Detailed reviews of the geochemical data and interpretations can be found in Zindler and Hart (1986), Silver et al. (1988), Carlson (1994), Hofmann (1997), Van Keken et al. (2002), Porcelli and Ballentine (2002), and Hauri(2002), and see Chapter 2.03.
Ballentine Chris J.
Hauri Erik H.
van Keken Peter E.
No associations
LandOfFree
Convective Mixing in the Earth's Mantle does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Convective Mixing in the Earth's Mantle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Convective Mixing in the Earth's Mantle will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1732201