The volcanic rocks of the Orca Group consist of thick to thin tabular bodies of altered tholeiitic basalt that have pillowed, massive, or crudely columnar flows and also include pillow breccia, aquagene tuff, and diabase or gabbro sills; pillows have palagonitic and amygdaloidal chilled margins (Winkler and Plafker, 1993).
A sequence of igneous rocks representing a fragment of oceanic lithosphere; composed mostly of peridotite overlain successfully by gabbro; sheeted basalt dikes, and pillow lava. Continental Slope The relativity steeply inclined part of the continental margin between the continental shelf and the continental rise or between the continental shelf ... Low δ34S values of sulfide in basalt lavas are consistent with microbial reduction of seawater sulfate within the volcanic rocks. Tectonic activity at the slow-spreading ridge allowed evolved formation waters to enter hot sheeted-dike complex basement, resulting in heating and precipitation of anhydrite.
May 06, 2018 · The stunning outcrop features tube-shaped blobs of basalt, each taller than a person, intertwined with one another like a mass of wriggling black worms. The pillows form when seawater quenches the exterior of the submarine lava flows while the hot interiors continue to expand as they fill with lava supplied by the sheeted dikes below. • Gold ± Bi, As, W, Mo, Sb, Te occurs in: single, planar, sheeted and stockwork quartz veins; disseminations in granites and skarns; and as infill in breccias. • Base metal contents are highly variable from almost absent to assemblages of Cu-Zn-Pb-As. Bi minerals may be well developed. • Alteration is variable in both style and intensity. 2
Sheeted dikes in basalt Gabbro Decompression melting at mid ocean ridge Hot mantle rises, decompresses, and melts. A thin dike intrudes Forming sheeted dikes, Occasionally erupts, spilling lava in “pillows.” Sediments are deposited on the spreading seafloor. Ophiolitic units present are serpentinized mantle peridotite, massive gabbro, sheeted dikes, pillow basalt and sheet flows, and epi-ophiolitic limestone and chert. Overlying this imbricated ophiolitic mélange is the younger Karadağ Formation, composed of radiolarian bearing pelagic limestone and chert. Peridotite Start studying ERS 103 Practice Exam. Learn vocabulary, terms, and more with flashcards, games, and other study tools.