Evidence of Carboniferous arc magmatism preserved in the Chicxulub impact structure

Abstract

Determining the nature and age of the 200-km-wide Chicxulub impact target rock is an essential step in advancing our understanding of the Maya Block basement. Few age constraints exist for the northern Maya Block crust, specifically the basement underlying the 66 Ma, 200 km-wide Chicxulub impact structure. The International Ocean Discovery Program-International Continental Scientific Drilling Program Expedition 364 core recovered a continuous section of basement rocks from the Chicxulub target rocks, which provides a unique opportunity to illuminate the pre-impact tectonic evolution of a terrane key to the development of the Gulf of Mexico. Sparse published ages for the Maya Block point to Mesoproterozoic, Ediacaran, Ordovician to Devonian crust are consistent with plate reconstruction models. In contrast, granitic basement recovered from the Chicxulub peak ring during Expedition 364 yielded new zircon U-Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) concordant dates clustering around 334 ± 2.3 Ma. Zircon rare earth element (REE) chemistry is consistent with the granitoids having formed in a continental arc setting. Inherited zircon grains fall into three groups: 400−435 Ma, 500−635 Ma, and 940−1400 Ma, which are consistent with the incorporation of Peri-Gondwanan, Pan-African, and Grenvillian crust, respectively. Carboniferous U-Pb ages, trace element compositions, and inherited zircon grains indicate a pre-collisional continental volcanic arc located along the Maya Block’s northern margin before NW Gondwana collided with Laurentia. The existence of a continental arc along NW Gondwana suggests southward-directed subduction of Rheic oceanic crust beneath the Maya Block and is similar to evidence for a continental arc along the northern margin of Gondwana that is documented in the Suwannee terrane, Florida, USA, and Coahuila Block of NE México.

Chicxulub impact structure, IODP‐ICDP Expedition 364 drill core: Geochemistry of the granite basement

“…In general, our results are consistent with previous studies on a more limited set of samples (see Zhao et al 2020;de Graaff et al 2021), and further support that the investigated granite unit could be related with arc magmatism during the closure of the Rheic ocean and Pangea assembly in the Carboniferous (Zhao et al 2020;Ross et al 2021). Conversely, a similar granite type was not sampled in any previous drill cores, including Y6 (Kettrup et al 2000;Kettrup and Deutsch 2003).…”

“…The apparent age of 273 AE Ma determined by the whole-rock errorchron (Fig. 11C), younger than the Carboniferous ages reported in Zhao et al (2020) and Ross et al (2021), indicates that the Rb-Sr system was likely disrupted (i.e., open system behavior), withiñ 50 Myr after granite crystallization and, thus, could account for another, older, metasomatic event that affected the Chicxulub granite unit. Following this event, the already altered granite was affected by postimpact hydrothermal overprint.…”

“…Granite (Zhao et al, 2020;de Graaff et al, of 0.705164 AE 0.0003. However, given the high uncertainty on age determination and its deviation from the well-constrained U-Pb Carboniferous ages obtained in zircons by Zhao et al (2020) and Ross et al (2021), this apparent age obtained from the errorchron corresponds to a disturbance of the Rb-Sr system (see the Discussion section).…”

“…Using the ages presented in both Zhao et al (2020) and Ross et al (2021), we can assume that these granites were probably emplaced during the Carboniferous. During this period, the Yucat an block was located at the edge of the Gondwana craton and recorded arc magmatism originating from the subduction of oceanic crust of the Rheic ocean beneath the northern edge of Gondwana before its collision with Laurentia (Pangean assembly) according to the geotectonic reconstructions of Dickinson and Lawton (2001).…”

“…Dating on the Hole M0077A granites was performed on zircon and yield late Paleozoic (Carboniferous) U-Pb ages of 326 AE 5 Ma (Rasmussen et al 2019;Zhao et al 2020) and 334 AE 2.3 Ma (Ross et al 2021). More recent ages (215 AE 28 to 260 AE 9 Ma) were obtained for allanite and probably recorded allanite growth during alteration events, while zircon ages represent the igneous crystallization (Wittmann et al 2018).…”