HR: 11:00h
AN: SF32A-03 INVITED     [Abstracts]
TI: Use of the PetDB Database for Calculating the Composition of the MORB-Source
AU: * Salters, V J
EM: salters@magnet.fsu.edu
AF: National High Magnetic Field Laboratory, 1800 E Paul Dirac Drive, Tallahassee, FL 32312 United States
AU: Stracke, A
EM: stracke@mpch-mainz.mpg.de
AF: Max-Planck-Institut fur Chemie, Postfach 3060, Mainz, 55020 Germany
AB: We used the PetDB database to obtain a large number of geochemical analyses of mid-ocean ridge basalts (MORB). These analyses were used to derive average MORB compositions, each fulfilling a number of different criteria, with the ultimate goal to constrain the composition of the mantle from which these rocks are derived by partial melting. Here, we will discuss search strategies to efficiently retrieve subsets of data from the PetDB. One of the largest advantages of the database is the possibility to select samples based on metadata. For example, for one of the average MORB compositions calculated, the compiled data were filtered to include only samples dredged from depths in excess of one thousand meters. Similarly, the ability to choose samples based on tectonic setting, freshness or any other non-chemical parameter is a convenient way to pre-select data by using non-chemical parameters. Extracting such non-chemical data from the literature would otherwise have been a tremendous task. Another advantage of databases is their ability to organize large amounts of data based on the individual needs of the user. However, during our "mining" of PetDB we had severe problems compiling large amounts of data. The present version of PetDB does not provide compilations (over the internet) that contain more than approximately 1000 samples. Given that by far more than 1000 analyses exist, even for individual ridge sections, this is a severe limitation of the PetDB. This is compounded by the fact that combination of smaller datasets requires significant manipulation because the number of geochemical parameters returned for each search is different depending on the availability of the selected parameters. It has been our experience that the present database is effective for retrieving small amounts of data. Retrieving the large amounts of geochemical analyses on global MORB (finally $>$5000 samples with more than 50 geochemical parameters were used), however, required development of strategies to retrieve the desired data. The pre-compiled data-sets offered recently by the PetDB, however, help using large datasets with a large number of geochemcial parameters. On the other hand, the interface of the PetDB does, at the moment, not provide more advanced methods of data selection, e.g. obtaining data within a certain range of a chemical parameter (for example La/Sm or Mg#). This is made possible in other interfaces (GEOROC) and allows selection of datasets for highly specialized purposes. In summary, the inability of the PetDB to handle large amounts of samples ($>$1000) required some effort to extract and combine small dataset into the ultimately required large compilation of geochemical analyses on a large number of data. Without the PetDB database, however, the compilation and calculation of averages would have been impossible to accomplish within a reasonable time frame.
DE: 9810 New fields (not classifiable under other headings)
DE: 1025 Composition of the mantle
DE: 1099 General or miscellaneous
SC: Special Focus: Advances in Data Acquisition, Management, Analysis and Display [SF]
MN: 2004 AGU Fall Meeting