Characterization of primary and secondary magnetite in marine 2 sediment by combining chemical and magnetic unmixing techniques

LUDWIG , R.EGLI , Q , S. BISHOP , V. CHERNENKO , T.FREDERICHS , G. RUGEL , S. MERCHEL , M. J. ORGEIRA

GLOBAL AND PLANETARY CHANGE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 p. 1 - 19

0921-8181

We present a novel technique for quantitative unmixing of primary and secondary ferrimagnetic minerals in 25 sediments. Hysteresis and high-resolution first-order reversal curve (FORC) measurements are performed on 26 sediment samples before and after digestion in a citrate?bicarbonate?dithionite (CBD) solution optimized for 27 maximumselective extraction of secondary fine-grained iron oxides. The difference betweenmagneticmeasure- 28 ments of untreated and CBD-treated sample materials is used to calculate the original magnetic signature of 29 CBD-extractable minerals. A combination of selective chemical extraction and magnetic measurements suited 30 for the detection of single-domain particles provides a cross-check between chemical and magnetic unmixing 31 of primary and secondary iron oxides and resolves the non-uniqueness problem of numerical unmixing 32 methods. A quantitative magnetic characterization of secondary ferrimagnetic minerals in a magnetofossil-rich 33 pelagic carbonate is presented for the first time. It can be used for calibration of recently developed fastmagnetic 34 unmixing techniques. CBD-based Fe extraction from sediments with minimal clastic and/or aeolian inputs, 35 such as pelagic carbonates, is particularly suited for the search for cosmogenic 60Fe signatures from supernova 36 explosions, because 60Fe dilution by dissolved primary Fe-bearing minerals is minimized