10.6084/m9.figshare.5480563.v1
C. S. Nelson
C. S.
Nelson
S. L. Nyman
S. L.
Nyman
K. A. Campbell
K. A.
Campbell
J. R. Rowland
J. R.
Rowland
Influence of faulting on the distribution and development of cold seep-related dolomitic conduit concretions at East Cape, New Zealand
Taylor & Francis Group
2017
Dolomitic conduit concretions
doughnut concretions
East Cape
New Zealand
faulting
gas hydrate dissociation
Late Miocene
methane-derived authigenic carbonate
2017-10-09 00:45:53
Dataset
https://tandf.figshare.com/articles/dataset/Influence_of_faulting_on_the_distribution_and_development_of_cold_seep-related_dolomitic_conduit_concretions_at_East_Cape_New_Zealand/5480563
<p>An intertidal shore platform in bathyal mudstones of the Late Miocene Pohutu Formation near East Cape, North Island, New Zealand, hosts many impressive dolomitic conduit concretions having predominantly doughnut morphologies up to 6 m across. Carbon isotope values (δ<sup>13</sup>C + 6 to + 9‰ PDB) are interpreted to show that the carbon for dolomite precipitation was derived from extensive anaerobic oxidation of thermogenic methane, while oxygen isotope values (δ<sup>18</sup>O + 2 to + 6‰ PDB) implicate the dissociation of gas hydrates at the time of carbonate precipitation. The concretions are inferred to mark the shallow sub-seafloor locations of upward migrating hydrocarbon-enriched fluids in a fossil cold seep system on a convergent margin. The distribution of concretions and faults are intimately associated. We propose that doughnut concretion growth was related to a periodically active fault-valve mechanism involving fluid pressure increase, fault rupture and fluid discharge, followed by fluid pressure decrease, mineral precipitation and fault sealing.</p>