page_title: Provenance (geology)
section_title: Bulk sediment Nd and Sr
hierarchical_section_title: Provenance (geology) / Examples of provenance methods / Bulk sediment Nd and Sr
caption_attribution_description: English: An example of Nd and Sr isotopic data plots, which are used in provenance studies
context_page_description: Provenance in geology, is the reconstruction of the origin of sediments. The Earth is a dynamic planet, and all rocks are subject to transition between the three main rock types: sedimentary, metamorphic, and igneous rocks. Rocks exposed to the surface are sooner or later broken down into sediments. Sediments are expected to be able to provide evidence of the erosional history of their parent source rocks. The purpose of provenance study is to restore the tectonic, paleo-geographic and paleo-climatic history.
  In the modern geological lexicon, "sediment provenance" specifically refers to the application of compositional analyses to determine the origin of sediments. This is often used in conjunction with the study of exhumation histories, interpretation of drainage networks and their evolution, and forward-modelling of paleo-earth systems. In combination, these help to characterise the "source to sink" journey of clastic sediments from hinterland to sedimentary basin.
context_section_description: Depend on properties of Sm–Nd radioactive isotope system can provide age estimation of sedimentary source rocks. It has been used in provenance studies. ¹⁴³Nd is produced by α decay of ¹⁴⁷Sm and has a half life of 1.06×10¹¹ years. Variation of ¹⁴³Nd/¹⁴⁴Nd is caused by decay of ¹⁴⁷Sm. Now Sm/Nd rato of the mantle is higher than that of the crust and ¹⁴³Nd/¹⁴⁴Nd ratio is also higher than in the mantle than in the crust. ¹⁴³Nd/¹⁴⁴Nd ratio is expressed in εNd notation (DePaolo and Wasserbur 1976). . CHUR refer to Chondritic Uniform Reservoir. So ϵNd is a function of T (time). Nd isotope evolution in mantle and crust in shown in the figure to the right. The upper plot (a), bold line shows the evolution of the bulk earth or CHUR(chondritic uniform reservoir). The lower plot (b) shows evolution of bulk earth (CHUR) crust and mantle, 143Nd/144Nd is transformed to εNd. Normally, the most rocks have εNd values in the range of -20 to +10. Calculated εNd value of rocks can be correlated to source rocks to perform provenance studies.What's more, Sr and Nd isotopes have been used to study both provenance and weathering intensity. Nd is mainly unaffected by weathering process but 87Sr/86Sr value is more affected by chemical weathering.
caption: An example of Nd and Sr isotopic data plots which are used in provenance studies
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