Publication Date:
2020-02-12
Description:
This study presents structural, geochronological, and petrological data from the Motagua Suture Zone (MSZ). The MSZ represents the northwestern Caribbean plate boundary in Guatemala and Honduras and consists of several sinistral transpressive shear and fault zones, separating the northern Maya Block (North American Plate) from the southern Chortis Block (Caribbean Plate). The Chortis Block originates from southern Mexico (Laurentia), the Maya block was formerly attached at the northern rim of Gondwana. Convergent motion between North and South America within the Middle to Late Mesozoic, and the subduction of the Farallon plate, resulted in a sinistral transpressive motion between the Chortis Block and the Maya Block. The goal of the study was to deduce a complete record of the early history of the Caribbean, which includes the characterization of different deformation phases and styles, and their correlation with the metamorphic evolution. Critical mineral parageneses were figured out and PT-paths were constructed. Results of quartz-c-axes texture analyses and Ar/Ar and U/Pb age dating were also incorporated to obtain a complete PTtd-path. Ductile structural features were evaluated to achieve the ductile contraction direction. Paleostress fields were calculated to assess the change of the principle stress directions in time. Summary, we gained six different deformation phases from the obtained data: High-grade deformation event D1 influenced basement rocks north of the Motagua fault at ~1 Ga during the Grenville orogeny, deformation event D2 accompanied by the Triassic/Jurassic breakup of Pangea, is conserved as subhorizontal foliation. Phase D3 is a ductile to brittle-ductile sinistral wrenching and thrusting event along the MSZ at 60 Ma to 68 Ma north of the Motagua fault; similar deformation occurred in the south at about 30 Ma to 40 Ma. This deformation characterizes the coeval eastward escape of the Chortis Block and the obduction of ophiolitic fragments onto the Maya and the Chortis Blocks. The latest events are represented by brittle dextral strike-slip (D4), sinistral strike-slip (D5), and normal faults (D6). Event D5 correlates well with Recent earthquakes. Petrological data indicate the activity of the MSZ during D3 as a transition zone of greenschist to amphibolite facies metamorphism, and a subsequent phase of cooling. Retrogression to the greenschist facies is evident within the Motagua Suture Zone, although definitive PT-conditions of this late stage cannot be calculated more precisely due to the absence of critical mineral assemblages. This study as well as other additional investigations may further light up the complex geology of this fascinating geotectonic setting.
Keywords:
550 - Earth sciences
Type:
info:eu-repo/semantics/conferenceObject
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