Sentence:  The gabbros from both the <WSD>Mid-Atlantic</WSD> Ridge and Mid-Indian Oceanic Ridge, showing a wide range in the FeO/MgO ratio (0.30–2.90), suggest a marked trend of fractionation (Fig. 1-3). 
Meaning of the word marked with <WSD> tags:  (Used as an attributive modifier in compounds such as "mid-Atlantic current" and "Mid-Atlantic Ridge"): located in, or otherwise relating to, the mid-Atlantic.