Geophysical evidence for an impact crater in vichada, northwestern south america and its economic potential

A prominent positive free-air gravity anomaly mapped over a roughly 50-km diameter basin is consistent with a mascon centered on (4°30'N, -69°15'W) in the Vichada Department, Colombia, South America. The inferred impact crater is nearly one third the size of the Chicxulub Crater. It must have formed recently, in the last 30 m.a because it controls the path of the Vichada River. The impact crater structure has been partially eroded and is almost completely covered by vegetation. No antipodal relationship has been established. The proposed impact appears to have contributed to the development of mineral deposits of economic interest. The impact shock waves extensively thinned and disrupted the Precambrian cratonic crust. Athick sedimentary cover, dense vegetation and erosional processes greatly limits direct geological testing of the inferred impact basin. Ground follow up gravity and magnetic surveys are recommended for confirming the regional free air gravity anomalies

Zircon U-Pb and (U-Th)/He thermochronology of the Santa Impact Crater (New Mexico, USA): evidence for a Paleozoic asteroid breakup?

The age of the Santa Fe Impact Structure (SFIS) is poorly constrained. Here, I examine the employability of the U-Th/He system in zircon and apatite extracted from shatter cones of the SFIS – some of which were previously analyzed for their U-Pb ages – to better constrain the age of this impact structure, which lacks a preserved melt sheet, and has a complex, post-impact tectonic and thermal history. To achieve this, zircon and apatite grains were separated from shatter cone samples. Grains were selected to span a range of apparent radiation damage to access a range of He retentivities. Where possible, grains preserving planar fractures (PFs) were also included. U-Th/He dates from apatite predominantly record cooling from Laramide burial (c. 60 Ma), correlating with published apatite fission track dates. In contrast, U-Th/He dates from zircon have a wider range (334.87 ± 13.56 Ma to 7.88 ± 0.22 Ma) and show a pronounced negative correlation with effective uranium content. The preservation of dates (n=3) that are older than the age of Laramide resetting in apatite demonstrates that low eU zircons are promising candidates for both recording and preserving the age of the impact. Therefore, further dating of low-eU zircons may provide evidence to support stratigraphic constraints that the Santa Fe impact age is roughly compatible with age estimates of ten other craters across North America, Europe and Africa, of variable (and lower) geochronological reliability. It is noteworthy that the age coincides with the estimated times of three asteroid breakup events documented to have occurred in the asteroid belt. I propose that both the age overlaps and geographic distributions of these impacts represent terrestrial evidence an asteroid breakup event. Finally, I also report the first planar fractures (PFs) in zircons sampled directly from the central uplift zone of the crater where shatter cone morphologies are preserved. The discovery of PFs in zircons increase the minimum pressure generated by the impact to at least 20 GPa, indicating a much larger crater (>>13 km diameter) than previously estimated

Geological Object Recognition in Extraterrestrial Environments

On July 4 1997, the landing of NASA’s Pathnder probe and its rover Sojourner marked the beginning of a new era in space exploration; robots with the ability to move have made up the vanguard of human extraterrestrial exploration ever since. With Sojourners landing, for the rst time, a ground traversing robot was at a distance too far from earth to make direct human control practical. This has given rise to the development of autonomous systems to improve the e?ciency of these robots,in both their ability to move,and their ability to make decisions regarding their environment. Computer Vision comprises a large part of these autonomous systems, and in the course of performing these tasks a large number of images are taken for the purpose of navigation. The limited nature of the current Deep Space Network means that a majority of these images are never seen by human eyes. This work explores the possibility of using these images to target certain features by using a combination of three AdaBoost algorithms and established image feature approaches to help prioritize interesting subjects from an ever growing data set of imaging data

A Targeted Investigation of the Upper Contact Unit of the Sudbury Igneous Complex in the North Range, Sudbury Impact Structure, Canada

The Sudbury Igneous Complex (SIC) represents the remnant of a crystalline impact melt sheet of the Sudbury impact structure; and is historically and presently a strategic exploration target sustaining the region\u27s prolific mining camp. In order to better understand the SIC, it is critical to investigate the chilled upper contact of the SIC, which has historically received little recognition. Through field observations, whole rock geochemistry, petrography, and electron microprobe analysis, this study concludes that the SIC upper contact is in fact extensive across the North Range of the SIC. Additionally, the geochemistry of the SIC units, offset dykes, and upper contact unit (UCU) of the SIC presented here lead to the conclusion that the UCU roof rocks represent a more accurate proxy than the offset dykes for the initial composition of the SIC. Finally, this study indicates that the UCU lithology is no longer considered an intrusive melt of the basal Onaping Formation breccias

Stable Cu, Fe, and Ni Isotopic Systematics of the Sudbury Offset Dikes and Associated Rocks

The stable isotope ratio compositions of Fe, Ni, and Cu (δ56Fe, δ60Ni, and δ65Cu) are reported for the first time in rocks from the Sudbury Igneous Complex (SIC). Massive sulfide ores, Quartz Diorite (QD), Inclusion bearing Quartz Diorite (IQD), and rocks from members of the Main Mass of the SIC were analyzed. The objective was to better understand the origin(s) and source(s) of the Offset Dikes and the associated sulfide mineralization. Based on stable isotope ratios and petrographic observations, two distinct types of sulfide mineralization hosted within the Offset Dikes are identified. Massive sulfide mineralization hosted within the Offset Dikes was identified to be different than the disseminated blebby sulfide mineralization found within the QD and IQD, based on coordinated isotopic and petrographic analyses. Comparisons of the stable isotope ratios of Fe, Ni, and Cu between rock samples from different Offset Dikes established a homogeneity in Fe, Ni, and Cu compositions. Including between the QD and IQD, and their disseminated sulfides. A correlation between δ60Ni, and δ65Cu values, with lighter compositions for the massive sulfides compared to the residual main mass, indicates an early magmatic origin for the massive sulfides compared to the disseminated sulfides contained in the Offset Dikes

Context is everything: an investigation of Spanish River Carbonatite and its effects on soil-plant-microorganism systems

With growing concerns about agricultural sustainability and food security, the use of rock fertilizers and agrominerals is receiving renewed interest. A wide variety of geological resources have been proposed as crop nutrient sources, with silicate rocks the predominant focus. Carbonatite rocks are known to weather more readily than silicate rocks; yet, they have received relatively little attention as it is thought their high Ca and Mg contents hinder effective nutrient release. However, there is strong evidence that the nutrients within carbonatite rocks are easily accessible to plants, and that these rocks have noticable effects on crop plant growth. Here I propose a framework to understand the mode of action of carbonatites on soil fertility and plant nutrition by integrating research at multiple scales, i.e., from individual plants to the ecosystem, including soil microorganisms. The model stems from greenhouse experiments on two crops, pea and wheat, and an extensive survey of the carbonatite deposit. It is emphasized that a systems-approach must be taken when examining carbonatites as their effects are strongly context-dependent, and there is evidence that a three-way interaction between plant-carbonatite-microorganisms is responsible for some of the observed effects on plants. The framework presented is intended not only to synthesize the current knowledge on carbonatites as rock fertilizers but also to guide future research on this and other similar geological resources