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GMPV2.1/GD2.7/SM4.2/TS1.4

Geochemical, petrological and physical discontinuities in the lithospheric mantle: supporting evidence and hypotheses for their origin (co-organized)
Convener: I. Ashchepkov  | Co-Convener: J. van Hunen 
Oral Programme
 / Mon, 23 Apr, 08:30–10:00  / Room 27
Poster Programme
 / Attendance Mon, 23 Apr, 10:30–12:00  / Hall XL
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Mantle discontinuities are the result of melt/fluid migration, mantle diapirism or subduction slab incorporation into subcratonic mantle. Recent results combine with great success geochemical, petrological, petrophysical and geophysical data to produce models of the evolution of the lithospheric mantle.
Key questions for studies of xenoliths in alkali basalts are: 1.Spatial and vertical metasomatic columns in permeable zones in subduction zones and plumes. 2. Determination of melt compositions using melt/fluid inclusions. 3. Pyroxenites and their parental melts. 4. Correlation of chemical and geophysical discontinuities.
Key questions for studies of xenoliths from the cratonic lithosphere are: 1. Characterisation and explanation of internal layering using petrological, geochemical and geophysical techniques . 2. growth mechanisms of the continental lithosphere and their evolution in time 3. types of mantle metasomatism and their relationship to tectonic setting 4. Mechanisms of melt migration through the lithosphere

Description of section
1. Layering of the craton keel.
Thermobarometric evidences of the discontinuities in the subcratonic lithospheric mantle (SCLM) (Griffin et al., 1996-2011; O’Reilly et al 1986; Bell et al ., 2003; Rudnick et al ., 1999; Kopylova et al ., 1999 ; Lehtonen et al ., 2004; etc ). The comparison of the different methods and thermobarometric models in application to the mantle layering (Nimis, Grutter, 2010 etc. Grutter et al., 2009 ). Reasons of the division if the mantle sequences in upper and lower part at 40-35 kbars (Ashchepkov et al., 2010). The agreement and disagreement of the thermobarometric with the lithosphere thickness obtained with geophysical methods (Pristley, McKenzie, 2006 etc). Evolution of the geothermal mantle regime in time (Ashchepkov et al 1986; Artemieva, 2009 )
2. Influence of the plumes or large mantle magmatic bodies of the geothermal regime (Smith, Lewis, 1999; Artemieva et al., 2009; Smith et al., 2009. Ayalew, Gibson,2009 etc).
3.Geochemical features of the separate startigraphic units or layers in SCLM and the possible interpritaion of their origin (Ionov et al., 2010 ). The geodynamic models of their original occurrence of the separate layers (Pearson, 1998; Jacob et al., 1993-2009). Comparison of the mantle sequences in different tectonic terrains within craton (Ashchepkov et al., 2011).
4.The evidences of the craton keel modification by the different type of metasomatism and interaction with the plum melts (Zhang, Duan, 2009; Ionov et al ., 2006; Tappe et a; ., 2007).
5.Dynamic of the craton keel destruction by the subduction tension accompanied by the weakening due to hydration by subduction related fluids (Xu,2001; Zhang et al ., 2005; Deng et al ., 2007 etc).
6.The models of the craton SCLM growth (Snyder, 2002; Snyder et al., 2009; Griffin et al., 2003-2010). Changes of the mechanisms of craton growth and destruction in time (Lee et al., 2010).
7.The PT facies of the mantle metasomatism for the different geodynamic environment (Magna et al ., 2008; Qin et al.,2010; Gregoire et al ., 2001; 2002,2003; Beccaluva et al., 2004; Matsumoto, et a ., 2000; Arai et al ., 2000-2010 etc ).
8.Types of the mantle peridotites and their origin in n different geodynamic settings (Bazylev, et al ., Ionov et al ., 1993-2010; Zheng et al ., 2008-2011; Wittig et al., 2008; Ntaflos et al., 2010; Hidas et al., 2007; ; Batanova et al., 2008 ).
9.Compositional major and trace element difference between garnet and spinel peridotites in various geodynamic environment in ancient and modern time and influence of the PT conditions to the compositions (McDonough, Sun, 1995; Robinson, Wood, 1998; Glaser et al ., 1999; Canil, 2004;Ionov et al., 2005; Zhang et al ., 2003;2008, Schmädicke et al., 2011 ). Problem of primitive mantle peridotites – ancient unmodified primordial mantle and refertilized by the anatexic of plum melts.
10.Eclogites. Types of eclogites and their origin – TGG cumulates or restites (Horodyskyj ey al ., 2007), subducted basalts or sediments. Special type of deep seated cumulates or metasomatites. Distribution of eclogites in mantle sequences in cratonic keel (Sobolev et al., 1987; (Jagouts et al , 1993; Snyder et al., 1993, Wyman, Kerrich, 2009; Spetcius et al.,2009;). Thermobarometry of the eclogites and their role in the mantle layering (Simakov, 2008; Brey et al., 1986 Peackly et al ., 2011). The role of eclogites in production of mantle melts and their hybridism with the plume melts (Sobolev et al ., 2006) Responsibility of the eclogites for the diamond grade (Sobolev et al., 1974- 2009).
11.Types mantle pyroxenites anatexic, magmatic. (Pokhilenko et al., 1999; Downes et al., 2007; Zhang, et al ., 2007; Aulbach et al ., 2009; Tinguely, et al ., 2008 Ashchepkov et al., 2011 ) Plume related and subduction related pyroxeniets their role in mantle layering and production of mantle melts.
12.Traps for the mantle melt in the SCLM. Lower 65-55 kbar for ultramafic, Middle 40 kbar for carbonatites, upper 30- 20 kbars for hydrous silicate melts (Tappe at l., 2007; Foley et al., 2011).
13 .Detection of mantle layering (Snyder et al., 2009) and subduction slabs (Koulakov et al., 2001-2010; Bonnardot et al., 2009; King et al ., 2007 Currie, et al., 2004 etc) in the mantle by geophysical methods. Correspondence between geochemical reservoir, geophysical discontinues and petrological or models of mantle (Anderson, 1995; Puchtel et al ., 1999 Korenaga, 2009; Hofmann. 2007 ).
14. Agreement between the S, SP, P – PP models for the detection of the mantle layering (Xu et al., 2008; Mooney, 2007; Chekunov et al ., 1997; Beloussov et al ., 1980). Geophysical models for mantle – compositional variations, presence of melt fluid (Braun, 2000; Walter, 2007; Schiano, 2003)or anisotropy of mantle rocks (olivine orientation as the result of flowing (Gatzemeier, Tommasi, 2006; Ismaı̈l, Mainprice, 1998).
15.Basalt geochemical features as the indicator of the difference in the mantle source lithology (Russo et al ., 2009; Sheth, 1999; Niu, et al ., 2002; Xu eta al., 2002; Jerram, Widdowson,2005 etc ).
16. Isotopic mantle domains and isotopic mantle stratification.
17. Mantle magmas as the source of the information for the mantle stratification and temporal and special evolution of mantle lithosphere
Public information: Public Information: This session is co-sponsored by the European Association of Geochemistry