Pb-Pb ages and Pb initial isotopic composition of lunar meteorites: new constrains on the timing of lunar magmatism and its mantle sources

2020 ◽  
Author(s):  
Renaud Merle ◽  
Alexander Nemchin ◽  
Martin Whitehouse ◽  
Joshua Snape ◽  
Gavin Kenny ◽  
...  
Keyword(s):  
Magmatic Activity ◽  
The Moon ◽  
Northwest Africa ◽  
Mantle Sources ◽  
Show Evidence ◽  
History Of ◽  
A Minor ◽  
Mare Basalts ◽  
Lunar Meteorites

<p>Constraining the duration of magmatic activity on the Moon is essential to understand how the lunar mantle evolved chemically through time. Determining age and initial isotopic compositions of mafic lunar meteorites is a critical step in defining the periods of magmatic activity that occurred during the history of the Moon and to constrain the chemical characteristics of mantle components involved in the sources of the magmas.</p><p>We have used the in-situ Pb–Pb SIMS technique to investigate lunar gabbros and basalts, including meteorites from the Northwest Africa (NWA) 773 clan (NWA 2727, NWA 3333, NWA 2977, NWA 773 and NWA 3170), LAP 02224, NWA 4734 and Dhofar 287A. These samples have been selected as they all belong to the dominant chemical group of low-titanium mare basalts and there is no clear agreement on their age. We have obtained ages of 2978 ± 13 Ma for LAP02224, 2981 ± 12 Ma for NWA 4734 and 3208 ± 22 Ma for Dhofar 287. For the NWA 773 clan, four samples (NWA 2727, NWA 773, NWA 2977, NWA 3170) yielded isochron-calculated ages that are identical within uncertainties with an average age of 3086.1 ± 4.8 Ma. The gabbroic sample NWA 3333 yielded an age of 3038 ± 20 Ma suggesting that two distinct magmatic events are recorded in the meteorites of the NWA 773 clan.</p><p>The entire age dataset from lunar mafic meteorites was screened to identify data that are problematic from an analytical viewpoint and/or show evidence of resetting and terrestrial contamination. This refined dataset combines the ages of mafic lunar meteorites and Apollo samples and suggests pulses in magmatic activity, with two main phases between 3350 and 3100 Ma and between 3900 and 3550 Ma followed by a minor phase at ~3000 Ma.</p><p>The evolution of the Pb initial ratios of the low-Ti mare basalts between 3400 Ma and 3100 Ma suggests that these rocks were progressively contaminated by a KREEP-like component. Nevertheless, the ~3000 Ma mafic rocks (NWA4734 and LAP02224) show significant differences in terms of initial <sup>204</sup>Pb/<sup>206</sup>Pb ratios that illustrates that the lunar mantle is probably more heterogeneous than has previously been assumed.</p>

The early chronology of the Moon: evidence for the early collisional history of the solar system

1977 ◽  
Vol 285 (1327) ◽  
pp. 97-103 ◽  
Keyword(s):  
Early Period ◽  
Gravitational Energy ◽  
Magmatic Activity ◽  
The Moon ◽  
Lunar Crust ◽  
Lunar Science ◽  
History Of ◽  
The One ◽  
Mare Basalts ◽  
Age Determinations

A major aim of lunar science has been to understand the early evolution to the lunar crust in the period prior to the extrusion of the mare basalts. There are two aspects to this early period of evolution about which age determinations provide information. On the one hand is the magmatic activity which led to the chemical differentiation of the outer regions of the Moon, while on the other is the bombardment of the Moon by large objects in the period immediately following its formation. The two aspects are probably not unrelated in that the bombardment may represent the final stages of the accretion of the Moon, and the heat source responsible for the initial differentiation was possibly the gravitational energy released during the major accretion phase. 40Ar-39Ar ages have been largely reset by the final stages of the bombardment and therefore most of the information obtained from argon measurements pertains to the chronology of the bombardment. Information on the magmatic activity is obtained from Rb-Sr, U, Th-Pb and Sm-Nd studies.

In situ Pb‐Pb dating of silica‐rich Northwest Africa ( NWA ) 6594 basaltic eucrite and its constraint on thermal history of the Vestan crust

2019 ◽  
Vol 54 (12) ◽  
pp. 3064-3081 ◽  
Author(s):  
Shiyong Liao ◽  
Weibiao Hsu ◽  
Ying Wang ◽  
Ye Li ◽  
Chipui Tang ◽  
...  
Keyword(s):  
Thermal History ◽  
Northwest Africa ◽  
History Of

scholarly journals Lunar exploration: opening a window into the history and evolution of the inner Solar System

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130315 ◽  
Author(s):  
Ian A. Crawford ◽  
Katherine H. Joy
Keyword(s):  
Solar System ◽  
Lunar Exploration ◽  
The Moon ◽  
Moon System ◽  
Origin And Evolution ◽  
The Earth ◽  
Geological Evolution ◽  
History Of ◽  
Rocky Planets

The lunar geological record contains a rich archive of the history of the inner Solar System, including information relevant to understanding the origin and evolution of the Earth–Moon system, the geological evolution of rocky planets, and our local cosmic environment. This paper provides a brief review of lunar exploration to-date and describes how future exploration initiatives will further advance our understanding of the origin and evolution of the Moon, the Earth–Moon system and of the Solar System more generally. It is concluded that further advances will require the placing of new scientific instruments on, and the return of additional samples from, the lunar surface. Some of these scientific objectives can be achieved robotically, for example by in situ geochemical and geophysical measurements and through carefully targeted sample return missions. However, in the longer term, we argue that lunar science would greatly benefit from renewed human operations on the surface of the Moon, such as would be facilitated by implementing the recently proposed Global Exploration Roadmap.

scholarly journals Heterogeneity in lunar anorthosite meteorites: implications for the lunar magma ocean model

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130241 ◽  
Author(s):  
Sara S. Russell ◽  
Katherine H. Joy ◽  
Teresa E. Jeffries ◽  
Guy J. Consolmagno ◽  
Anton Kearsley
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Ocean Model ◽  
Magma Source ◽  
The Moon ◽  
Magma Ocean ◽  
Element Abundances ◽  
Wide Range ◽  
Lunar Meteorites

The lunar magma ocean model is a well-established theory of the early evolution of the Moon. By this model, the Moon was initially largely molten and the anorthositic crust that now covers much of the lunar surface directly crystallized from this enormous magma source. We are undertaking a study of the geochemical characteristics of anorthosites from lunar meteorites to test this model. Rare earth and other element abundances have been measured in situ in relict anorthosite clasts from two feldspathic lunar meteorites: Dhofar 908 and Dhofar 081. The rare earth elements were present in abundances of approximately 0.1 to approximately 10× chondritic (CI) abundance. Every plagioclase exhibited a positive Eu-anomaly, with Eu abundances of up to approximately 20×CI. Calculations of the melt in equilibrium with anorthite show that it apparently crystallized from a magma that was unfractionated with respect to rare earth elements and ranged in abundance from 8 to 80×CI. Comparisons of our data with other lunar meteorites and Apollo samples suggest that there is notable heterogeneity in the trace element abundances of lunar anorthosites, suggesting these samples did not all crystallize from a common magma source. Compositional and isotopic data from other authors also suggest that lunar anorthosites are chemically heterogeneous and have a wide range of ages. These observations may support other models of crust formation on the Moon or suggest that there are complexities in the lunar magma ocean scenario to allow for multiple generations of anorthosite formation.

scholarly journals The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205

2014 ◽  
Vol 49 (2) ◽  
pp. 261-291 ◽  
Author(s):  
Stephen M. Elardo ◽  
Charles K. Shearer ◽  
Amy L. Fagan ◽  
Lars E. Borg ◽  
Amy M. Gaffney ◽  
...  
Keyword(s):  
Northwest Africa ◽  
Mare Basalts ◽  
Lunar Meteorites

scholarly journals North polar trough formation due to in-situ erosion as a source of young ice in mid-latitudinal mantles on Mars

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Alexis P. Rodriguez ◽  
Kenneth L. Tanaka ◽  
Ali M. Bramson ◽  
Gregory J. Leonard ◽  
Victor R. Baker ◽  
...  
Keyword(s):  
Katabatic Wind ◽  
Spiral Pattern ◽  
Near Surface ◽  
Valuable Source ◽  
History Of ◽  
North Polar ◽  
Human Exploration ◽  
Erosional Event

AbstractThe clockwise spiral of troughs marking the Martian north polar plateau forms one of the planet’s youngest megastructures. One popular hypothesis posits that the spiral pattern resulted as troughs underwent poleward migration. Here, we show that the troughs are extensively segmented into enclosed depressions (or cells). Many cell interiors display concentric layers that connect pole- and equator-facing slopes, demonstrating in-situ trough erosion. The segmentation patterns indicate a history of gradual trough growth transversely to katabatic wind directions, whereby increases in trough intersections generated their spiral arrangement. The erosional event recorded in the truncated strata and trough segmentation may have supplied up to ~25% of the volume of the mid-latitude icy mantles. Topographically subtle undulations transition into troughs and have distributions that mimic and extend the troughs’ spiraling pattern, indicating that they probably represent buried trough sections. The retention of the spiral pattern in surface and subsurface troughs is consistent with the megastructure’s stabilization before its partial burial. A previously suggested warm paleoclimatic spike indicates that the erosion could have occurred as recently as ~50 Ka. Hence, if the removed ice was redeposited to form the mid-latitude mantles, they could provide a valuable source of near-surface, clean ice for future human exploration.

RECENT INVESTIGATIONS AT TULA CHICO, TULA, HIDALGO

2021 ◽  
Vol 32 (1) ◽  
pp. 41-55
Author(s):  
Robert H. Cobean ◽  
Dan M. Healan ◽  
María Elena Suárez
Keyword(s):  
Classic Period ◽  
Cultural Continuity ◽  
Direct Control ◽  
Early Postclassic ◽  
Initial Settlement ◽  
Show Evidence ◽  
History Of

AbstractRecent excavations at Tula Chico, the monumental center for Tula's earliest settlement, revealed a long and complex history of occupation, beginning with its initial settlement in the Middle Classic period by Coyotlatelco peoples, when much of the region was under Teotihuacan's direct control. During the Epiclassic period, a program of monumental construction began that developed the monumental complex seen today over a period of about 200 years. Although Tula Chico was superseded by Tula Grande, the monumental center for the Early Postclassic city, it continued to be occupied and maintained until its destruction by fire. Tula Chico and Tula Grande show evidence of clear cultural continuity in ceramics, architecture, and sculpture, including “Toltec style” sculpture characteristic of Tula Grande that is present in temporally early contexts at Tula Chico.

scholarly journals Development of a Field Deployable Firebrand Flux and Condition Measurement System

2020 ◽  
Author(s):  
Simone Zen ◽  
Jan C. Thomas ◽  
Eric V. Mueller ◽  
Bhisham Dhurandher ◽  
Michael Gallagher ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Time History ◽  
Infrared Camera ◽  
Thermal Conditions ◽  
Particle Characterization ◽  
Fire Dynamics ◽  
Rate Of Spread ◽  
New Instrument ◽  
History Of

AbstractA new instrument to quantify firebrand dynamics during fires with particular focus on those associated with the Wildland-Urban Interface (WUI) has been developed. During WUI fires, firebrands can ignite spot fires, which can rapidly increase the rate of spread (ROS) of the fire, provide a mechanism by which the fire can pass over firebreaks and are the leading cause of structure ignitions. Despite this key role in driving wildfire dynamics and hazards, difficulties in collecting firebrands in the field and preserving their physical condition (e.g. dimensions and temperature) have limited the development of knowledge of firebrand dynamics. In this work we present a new, field-deployable diagnostic tool, an emberometer, designed to provide measurement of firebrand fluxes and information on both the geometry and the thermal conditions of firebrands immediately before deposition by combining a visual and infrared camera. A series of laboratory experiments were conducted to calibrate and validate the developed imaging techniques. The emberometer was then deployed in the field to explore firebrand fluxes and particle conditions for a range of fire intensities in natural pine forest environments. In addition to firebrand particle characterization, field observations with the emberometer enabled detailed time history of deposition (i.e. firebrand flux) relative to concurrent in situ fire behaviour observations. We highlight that deposition was characterised by intense, short duration “showers” that can be reasonably associated to spikes in the average fire line intensity. The results presented illustrate the potential use of an emberometer in studying firebrand and spot fire dynamics.

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