Analysis of Mn-nodules from Leg 51

Rhodochrosite crystals and manganese oxide micronodules which have formed in situ are found in abundance at depth (76.5 to 106.5 m) in Hole 417A. A gradual transformation of the rhodochrosite to manganese oxide micronodules is observed in many grains throughout the interval. The transformation proce...

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Bibliographic Details
Main Authors: Borella, Peter E, Adelseck, C
Format: Dataset
Language:English
Published: PANGAEA 1980
Subjects:
51-417A
Deep Sea Drilling Project
DRILL
Drilling/drill rig
DSDP
Glomar Challenger
Leg51
NOAA and MMS Marine Minerals Geochemical Database
NOAA-MMS
North Atlantic/CONT RISE
North Atlantic
Online Access:https://doi.pangaea.de/10.1594/PANGAEA.872489
https://doi.org/10.1594/PANGAEA.872489
Description
Summary:Rhodochrosite crystals and manganese oxide micronodules which have formed in situ are found in abundance at depth (76.5 to 106.5 m) in Hole 417A. A gradual transformation of the rhodochrosite to manganese oxide micronodules is observed in many grains throughout the interval. The transformation process initially attacks the edge of the rhodochrosite crystal and proceeds inward, first forming a pseudomorph of the crystal. Some grains exhibit varying degrees of departure from the crystal shape of a true pseudomorph, suggesting either an overgrowth of manganese oxide or late-stage destruction of the pseudomorph. No significant differences were observed in the relative per cent of minor and trace metals when comparing the pure rhodochrosite with the manganese oxide pseudomorphs. This suggests that the manganese and other trace elements were not transported into the system but were incorporated directly from the rhodochrosite as the manganese oxide formed. Grains which did not exhibit pseudomorphic form showed enrichment in some trace elements. We postulate that the diagenetic environment changed from reducing to oxidizing. How and when this change occurred in the sedimentary column remains an enigma.

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