A new analysis of jade found along the Motagua fault that bisects Guatemala is underscoring the fact that this region has a more complex geologic history than previously thought.
Because jade and other associated metamorphic rocks are found on both sides of the fault, and because the jade to the north is younger by about 60 million years, a team of geologists posits in a new research paper that the North American and Caribbean plates have done more than simply slide past each other: they have collided. Twice.
"Now we understand what has happened in Guatemala, geologically," says one of the authors, Hannes Brueckner, Professor of Geology at Queens College, City University of New York. "Our new research is filling in information about plate tectonics for an area of the world that needed sorting."
Jade is a cultural term for two rare metamorphic rocks known as jadeitite (as discussed in the current research) and nephrite that are both extremely tough and have been used as tools and talismans throughout the world. The jadeitite (or jadeite jade) is a sort of scar tissue from some collisions between Earth's plates. As ocean crust is pushed under another block, or subducted, pressure increases with only modest rise in temperature, squeezing and drying the rocks without melting them. Jade precipitates from fluids flowing up the subduction channel and into the chilled, overlying mantle that becomes serpentinite. The serpentinite assemblage, which includes jade and has a relatively low density, can be uplifted during subsequent continental collisions and extruded along the band of the collision boundary, such as those found in the Alps, California, Iran, Russia, and other parts of the world.
The Motagua fault is one of three subparallel left-lateral strike-slip faults (with horizontal motion) in Guatemala and forms the boundary between the North American and Caribbean tectonic plates. In an earlier paper, the team of authors found evidence of two different collisions by dating mica found in collisional rocks (including jade) from the North American side of the fault to about 70 million years ago and from the southern side (or the Caribbean plate) to between 120 and 130 million years ago. But mica dates can be "reset" by subsequent heating. Now, the authors have turned to eclogite, a metamorphic rock that forms from ocean floor basalt in the subduction channel. Eclogite dates are rarely reset, and the authors found that eclogite from both sides of the Motagua dates to roughly 130 million years old.
The disparate dating of rocks along the Motagua can be explained by the following scenario: a collision 130 million years ago created a serpentinite belt that was subsequently sliced into segments. Then, after plate movement changed direction about 100 million years ago, a second collision between one of these slices and the North American plate reset the mica clocks in jadeitite found on the northern side of the fault to 70 million years. Finally, plate motion in the last 70 million years juxtaposed the southern serpentinites with the northern serpentinites, which explains why there are collisional remnants on both sides of the Motagua.
"All serpentinites along the fault line formed at the same time, but the northern assemblage was re-metamorphosed at about 70 million year ago. There are two collision events recorded in the rocks observed today, one event on the southern side and two on the northern," explains author George Harlow, Curator in the Division of Earth and Planetary Sciences at the American Museum of Natural History. "Motion between plates is usually not a single motion—it is a series of motions.
This research was published in Earth and Planetary Science Letters. In addition to Brueckner and Harlow, authors on this research paper include Hans Lallemant of Rice University in Houston, Texas; Virginia Sisson of the University of Houston in Texas; Sidney Hemming of Columbia University's Lamont-Doherty Earth Observatory, New York; Uwe Martens of Stanford University, California; Tatsuki Tsujimori of Okayama University in Japan, and Sorena Sorenson of the National Museum of Natural History in Washington, D.C. The National Science Foundation funded the research.
Kristin Elise Phillips | EurekAlert!
New plate adds plot twist to ancient tectonic tale
15.08.2017 | Rice University
Global warming will leave different fingerprints on global subtropical anticyclones
14.08.2017 | Institute of Atmospheric Physics, Chinese Academy of Sciences
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).
The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
16.08.2017 | Physics and Astronomy
16.08.2017 | Materials Sciences
16.08.2017 | Interdisciplinary Research