Y. Hsueh-Wen S.H. Gunn A. E. Gibbs W. Chung-ho J.R. Hein 1994 <p><span>Ironstones recovered from five Late Cretaceous seamounts in the central Pacific region probably formed during late-stage edifice-building volcanism. Ironstones are dense and compact with the appearance of brown chert. The ironstones are characterized by a goethite mineralogy with FeOOH contents up to 88%, extreme fractionation of Fe and Mn, low trace-element and rare earth element abundances, low&nbsp;</span><span class="math"><span id="MathJax-Element-1-Frame" class="MathJax_SVG" data-mathml="<math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;><mtext>Co</mtext><mtext>Zn</mtext></math>"><span class="MJX_Assistive_MathML">CoZn</span></span></span><span>&nbsp;ratios, and isotopic equilibration temperatures of about 20–45 °C. These characteristics indicate that the ironstones formed from hydrothermal fluids. Ironstones probably formed below the seawater-seafloor interface, as indicated by their occurrence as a proximal hydrothermal deposit, presence of primary goethite cement, pervasive replacement of rocks by goethite, and absence of interbedded pyro-clastic beds.</span></p> application/pdf 10.1016/0016-7037(94)90455-3 en Elsevier Composition and origin of hydrothermal ironstones from central Pacific seamounts article