2001. Secular geochemistry of central puerto rican island arc lavas: Constraints on mesozoic tectonism in the eastern greater antilles. Journal of Petrology 42 (12) (DEC): 2197-214.

2001. Secular geochemistry of central puerto rican island arc lavas: Constraints on mesozoic tectonism in the eastern greater antilles. Journal of Petrology 42 (12) (DEC): 2197-214.

Bimodal volcanism in northeast Puerto Rico and the Virgin Islands (Greater Antilles Island Arc): Genetic links with Cretaceous subduction of the mid-Atlantic ridge Caribbean spur

Jolly, Wayne T., Edward G. Lidiak, and Alan P. Dickin. 2008. Bimodal volcanism in northeast puerto rico and the virgin islands (greater antilles island arc): Genetic links with cretaceous subduction of the mid-atlantic ridge caribbean spur. Lithos 103 (3-4) (JUL): 393-414.

Bimodal extrusive volcanic rocks in the northeast Greater Antilles Arc consist of two interlayered suites, including (1) a predominantly basaltic suite, dominated by island arc basalts with small proportions of andesite, and (2) a silicic suite, similar in composition to small volume intrusive veins of oceanic plagiogranite commonly recognized in oceanic crustal sequences. The basaltic suite is geochemically characterized by variable enrichment in the more incompatible elements and negative chondritenormalized HFSE anomalies. Trace element melting and mixing models indicate the magnitude of the subducted sediment component in Antilles arc basalts is highly variable and decreases dramatically from east to west along the arc. In the Virgin Islands, the sediment component ranges betweenb0.5 to ∼1% in Albian rocks, and between ∼1 and 2% in succeeding Cenomanian to Campanian strata. In comparison, sediment proportions in central Puerto Rico range between 0.5 to 1.5% in the Albian to 2 toN4% during the Cenomanian-Campanian interval. The silicic suite, consisting predominantly of rhyolites, is characterized by depleted Al2O3 (averageb16%), low Mg-number (molar Mg/Mg+Feb0.5), TiO2 (b1.0%), and Sr/Y (b10), oceanic or arc-like Sr, Nd, and Pb isotope signatures, and by the presence of plagioclase. All of these features are consistent with an anatexic origin in gabbroic sources, of both oceanic and arc-related origin, within the sub-arc basement. The abundance of silicic lavas varies widely along the length of the arc platform. In the Virgin Islands on the east, rhyolites comprise up to 80% of Lower Albian strata (112 to 105 Ma), and about 20% in post-Albian strata (105 to 100 Ma). Farther west, in Puerto Rico, more limited proportions (b20%) of silicic lavas were erupted. The systematic variation of both sediment flux and abundance of crustally derived silicic lavas are consistent with current tectonic models of Caribbean evolution involving approximately perpendicular subduction of the Caribbean spur of the mid-Atlantic Ridge, which was located approximately midway between North and South America until Campanian times. Within this hypothetical setting the centrally positioned Virgin Islands terrain remained approximately fixed above the subducting ridge as the Antilles arc platform swept northeastward into the slot between the Americas. Accordingly, heat flow in the Virgin Islands was elevated throughout the Cretaceous, giving rise to widespread crustal melting, whereas the subducted sediment flux was limited. Conversely, toward the west in central Puerto Rico, which wasconsistently more remote from the subducting ridge, heat flow was relatively low and produced limited crustal melting, while the sediment flux was comparatively elevated.

Vertical motions of the Puerto Rico Trench and Puerto Rico and their cause

ten Brink US (2005) Vertical motions in the Puerto Rico trench and
Puerto Rico and their cause. J Geophys Res 100:B06404. doi:

The Puerto Rico trench exhibits great water depth, an extremely low gravity anomaly, and a tilted carbonate platform between (reconstructed) elevations of +1300 m and 4000 m. I argue that these features are manifestations of large vertical movements of a segment of the Puerto Rico trench, its forearc, and the island of Puerto Rico that took place 3.3 m.y. ago over a time period as short as 14–40 kyr. I explain these vertical movements by a sudden increase in the slab’s descent angle that caused the trench to subside and the island to rise. The increased dip could have been caused by shearing or even by a complete tear of the descending North American slab, although the exact nature of this deformation is unknown. The rapid (14–40 kyr) and uniform tilt along a 250 km long section of the trench is compatible with scales of mantle flow and plate bending. The proposed shear zone or tear is inferred from seismic, morphological, and gravity observations to start at the trench at 64.5Wand trend southwestwardly toward eastern Puerto Rico. The tensile stresses necessary to deform or tear the slab could have been generated by increased curvature of the trench following a counterclockwise rotation of the upper plate and by the subduction of a large seamount.

Structure and tectonics of the upper Cenozoic Puerto Rico- Virgin Islands carbonate platform as determined from seismic reflection studies

van Gestel, J.-P., P. Mann, J. F. Dolan, and N. R. Grindlay (1998), Structure
and tectonics of the upper Cenozoic Puerto Rico-Virgin Islands carbonate
platform as determined from seismic reflection studies, J. Geophys. Res.,
103, 30,505– 30,530.

The Puerto Rico-Virgin Islands carbonate platform was deposited over an area of 18,000 km2 from early Oligocene to Holocene on top of an inactive and subsiding Cretaceous-earliest Oligocene island arc. Regional single-channel and multichannel seismic reflection lines presented in this study provide the first information on the regional stratigraphy and structure of this platform that has previously been known mainly from onshore stratigraphic sections of a relatively small (2250 km2) portion of the platform exposed by late Neogene tectonic uplift along the north coast of Puerto Rico. Seismic reflection lines are used to map the thickness of the carbonate platform strata and to correlate this thickness with onshore outcrop and well data from northern and southern Puerto Rico, St. Croix (U.S. Virgin Islands), and the Saba Bank. Limestone thickness variations from a little over 2 km to almost zero are used to subdivide the Puerto Rico-Virgin Islands platform into five distinct carbonate provinces: (1) north Puerto Rico area including the onshore exposures; (2) Virgin Islands area; (3) St. Croix and Saba Bank area; (4) south Puerto Rico area; and (5) Mona Passage area. Carbonate thickness and structural information from each area are used to test five previously proposed models for the deformation and vertical movements of the platform. The most prominent feature of the platform in the Puerto Rico-Virgin Islands area is a large, east-west trending arch. The northern limb of this arch exhibits a smoother, more uniform dip than the steeper, more abruptly faulted, southern limb. The core of the arch is responsible for the exposure of arc basement rocks on Puerto Rico. The origin of this arch, which occurs over a 300 km wide area, is best explained by north-south shortening and arching, caused by interaction at depth of subducted slabs of the North America and Caribbean plates. Other important evidence for this model can be found in the Benioff zones observed in the earthquake profiles. Loading of the Caribbean plate results in downward flexing of the North America plate and causes the 4 km subsidence of the carbonate platform north of Puerto Rico.
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