Mathematics – Logic
Scientific paper
Jan 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999nvm..confq..59s&link_type=abstract
Workshop on New Views of the Moon 2: Understanding the Moon Through the Integration of Diverse Datasets, p. 59
Mathematics
Logic
Core-Mantle Boundary, Igneous Rocks, Lunar Maria, Basalt, Lunar Geology, Earth Crust, Europium Isotopes, Fractionation, Geological Faults, Lithosphere, Lunar Crust, Mid-Ocean Ridges, Petrogenesis
Scientific paper
(1) Maria with mafic basaltic floors are the second major type of morphostructures of the Moon, which were formed in the late stages of its evolution from 3.8 to 3.2 Ga. They form large rounded depressions (10-km depths) in the lunar relief. On their structure (presence of mid-maria moundlike rises and local rises), and on basaltic rocks composition they resemble oceanic segments of the Earth with its mid-oceanic ridges and within-plate oceanic islands. These types of the Earth's structures also began to form later than continental segments of the lithosphere, from ca. Ga. (2) Like on the Earth, two types of basalts are typical for the lunar maria: low-Ti and high-Ti, which could be correlated with the midoceanic ridge basalts (MORB) and oceanic island Fe-Ti basalts (0113) consequently. This type of tectonic-magmatic activity survived until now on the Earth; its petrogenesis associated with ascending of the mantle plumes that originated on the core-mantle boundary (CMB), in the layer D". For the terrestrial plumes it is characteristically a presence of specific fluid components, enriched in Fe, Ti, alkalies, -, - -, Zr, - - -, etc. Concentration of the fluid components is low in MORB and the highest in the within-plate Fe-Ti basalts. (3) Ocean-island basalt magmatism has a limited range in the Earth's oceans and is often localized on the mid-oceanic ridge slopes or far from them. With distance from the ridges axes composition of melts became more alkaline and titaniferous. The same picture is common for the continental traps provinces, whose origin is linked with superplume ascension; close to the MORB tholeiitic basalts are predominate, and alkaline Fe-Ti basalts present in a limited range. Traps appearance often preceded oceans opening and in this sense they could be defined as the first stage of the ocean development. (4) By analogy of the Earth, it is suggested that petrogenesis of the mare basalts could be also linked with plume activity, which were ascended from the lunar CMB of that time. Instead of the Earth, the lunar outer (liquid) core did not survive until present, but had to be active during the maria formation. The main difference of a fluid components of these plumes from the Earth's analog was the practical absence of H20 in them; this indicates a mineral composition of the mare basalts, where important role-play mineral phases formed under reduce conditions. (5) Another important difference is linked with the lunar high-Ti basalts, which are characterized by a strong negative Eu anomaly;however, such an anomaly has not been found in the very low-Ti (VLT) varieties. Traditionally, the presence of such an anomaly is associated with fractionation of plagioclase in magmatic processes. However, we suggest that in this particular case this phenomenon is more likely linked with reduced character of the Moon interior, because in magmatic systems a value of EU2,/EU3+ ratio depends on f(O2), and in reducing systems all Eu is represented by EU2+, which accumulated in the basic plagioclase. In contrast to the terrestrial basalts, where both Eu isotopes occur and removing one of them smoothed off through accumulation of the second, here only EU2+ occurred and so its fractionation led to strong depletion of the residual melt in Eu. Consequently, appearance of the Eu anomaly could be linked with fractionation of plagioclase in transitional magmatic chambers (intrusions) in the form of different gabbroids. Because Eu content in basalts quickly rises under growth of Ti, this process is most effective in the case of the high-Ti melts. (6) Beneath the lunar maria excess of masses (mascones) occurs and the lunar crust becomes thinner above them. In general, such a situation resembles a character of distribution of Earth's crust above continental rifts. Probably, the mascones are solidified mantle-plume head, which are known on the Earth as large lens like bodies of anomalous mantle beneath mid-oceanic ridges and continental rift zones. (7) So, there are essential similarities in structure and origin of the lunar maria and terrestrial oceans. However, instead of the Earth, the ancient lunar crust did not disrupt with formation of the lithosphere of oceanic type and further development according to a plate-tectonics model. The process ended on the first stage, analogous to the terrestrial continental traps formation.
Bogatikov O. A.
Sharkov E. V.
No associations
LandOfFree
Mare Magmatism of the Moon and Oceanic Magmatism of the Earth: Similarities and Distinctions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Mare Magmatism of the Moon and Oceanic Magmatism of the Earth: Similarities and Distinctions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mare Magmatism of the Moon and Oceanic Magmatism of the Earth: Similarities and Distinctions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1276595