<i>Radiogenic Isotope Geology</i>

Dickin, A. P.; Muller, Richard P.

doi:10.1063/1.2807660

Cited by 166 publications

(235 citation statements)

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“…9 and Tabl 13) suggests that the Nd model ages [19] could be indicative of the main metasomatic event affecting the lithospheric sources beneath the PdS region. These ages (calculated in relation to the depleted mantle, TDM, Table 13; [51]) for the whole PdS population (12 samples) are 1.05±0.08 Ga, which is similar to those calculated for the APIP kamafugites, i.e., TDM=0.97±0.09 Ga (44 samples, cf. inset of Fig.…”

Section: Sr-nd Isotopessupporting

confidence: 78%

Petrology of potassic alkaline ultramafic and carbonatitic rocks from Planalto da Serra (Mato Grosso State), Brazil

Comin-Chiaramontí¹,

Gomes²,

Min³

et al. 2014

Open Geosciences

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Abstract:The Planalto da Serra igneous rocks form plugs, necks and dykes of carbonate-rich ultramafic lamprophyres (aillikites and glimmerites with kamafugitic affinity) and carbonatites (alvikites and beforsites). Phlogopite and/or tetraphlogopite, diopside and melanitic garnet are restricted to aillikitic rock-types, whereas pyroclore occurs only in carbonatites. Aillikites and carbonatites are altered to hydrotermalites, having chlorite and serpentine as dominant minerals. Planalto da Serra igneous rock association has kamafugitic affinity (i.e. effusive, ultrapotassic. High LREE/HREE fractionation, incompatible elements data and Sr-Nd isotopes, suggest that the K-ultramafic alkaline and carbonatite rocks originated from a variably metasomatized mantle source enriched in radiogenic Sr. Crustal contamination is negligible or absent. Age values of 600 Ma rule out the geochronological relationship between the investigated intrusions and the Mesozoic alkaline bodies from the Azimuth 125 • lineament. The TDM model ages allow to conclude that Planalto da Serra magma is derived from the partial melting of a mantle source metasomatised by K-rich carbonatated melt during the Early to Late Neoproterozoic. On the basis of alkaline magmatism repetitions at 600 Ma and 90-80 Ma we question the subsistence of a stationary mantle plume for so long time. Keywords

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Section: Sr-nd Isotopessupporting

confidence: 78%

Petrology of potassic alkaline ultramafic and carbonatitic rocks from Planalto da Serra (Mato Grosso State), Brazil

Comin-Chiaramontí¹,

Gomes²,

Min³

et al. 2014

Open Geosciences

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“…However, 187 Os/ 188 Os and 187 Re/ 188 Os ratios are fairly constant, and the relative differences are 0.69% and 0.92%, respectively. This observation can be explained by "nugget effect" as has been pointed out for heterogeneous Os distribution in rocks and minerals (e.g., Dickin, 1995). In the present case, Re and Os are concentrated together in a phase to maintain constant Re/Os ratios, although such Re and Os concentrated mineral remains unknown.…”

Section: Resultssupporting

confidence: 62%

Re-Os dating of the Kuroko ores from the Wanibuchi Mine, Shimane Prefecture, southwestern Japan.

Terakado

2001

Geochem. J.

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Re-Os dating method was applied to the Kuroko ores from of the Wanibuchi Mine, southwestern Japan. Two whole-rock Kuroko ores and two yellow color fragments separated from one Kuroko ore sample were analyzed. Their Re and Os concentrations range from 3.52 to 50.6 ppb and from 20.1 to 92.9 ppt, respectively, and their 187 Os/ 188 Os ratios vary from 0.911 to 1.609. These data yield an isochron age of 18.44 ± 0.60 Ma with initial 187 Os/ 188 Os of 0.621 ± 0.013. The age is older than the inferred Kuroko formation age of northeastern Kuroko deposits, and also about three Ma older than the time of the clockwise rotation of southwestern Japan (ca. 15 Ma). The Wanibuchi Kuroko deposits are considered to have formed at the waning stage of the first phase (28-18 Ma) of the rifting and seafloor spreading in the Japan Sea area. The initial 187 Os/ 188 Os ratio might reflect the contemporaneous local seawater ratio that was more affected by mantle-derived Os resulted from the volcanic activities of Japan Sea formation than the typical oceanic Os ratio.

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“…Until recently, the most promising method for establishing an accurate chronology of the polar stratigraphy appeared to be isotopic dating techniques based on the identification of horizons containing either ' O B~ (with recent peaks produced by local supernova events 35 and 60 ka BP; Beer et al 1992) or volcanic ash (to which standard argon-dating techniques could then be applied; Dicken 1995). Either approach requires analytical capabilities and resources that greatly exceed those that might conceivably be employed in situ by robotic spacecraft, necessitating the remote acquisition, preservation, and return of drill core samples (tens to hundreds of meters in length) back to Earth for analysis.…”

Section: Outstanding Issues and Needed Capabilitiesmentioning

confidence: 99%

The State and Future of Mars Polar Science and Exploration

Clifford

2000

Icarus

110

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20, 1999; revised October 25, 1999 As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of -lo6 km2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young-preserving a record of the seasonal and climatic cycling of atmospheric COz, H20, and dust over the past NIO~-IO~ years..For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet--documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason-providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.

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Radiogenic Isotope Geology

Cited by 166 publications

References 0 publications

Petrology of potassic alkaline ultramafic and carbonatitic rocks from Planalto da Serra (Mato Grosso State), Brazil

Petrology of potassic alkaline ultramafic and carbonatitic rocks from Planalto da Serra (Mato Grosso State), Brazil

Re-Os dating of the Kuroko ores from the Wanibuchi Mine, Shimane Prefecture, southwestern Japan.

The State and Future of Mars Polar Science and Exploration

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