Geochemistry and Geochronology of Circumferential Dykes of the Franklin LIP: A Rotated Perspective on Plate Reconstruction

In addition to an extrusive volcanic component and associated sills,the Neoproterozoic Franklin Large Igneous Province(LIP)comprises a giant radiating dyke swarm spanning an arc of ca.110?,as well as a less-

Biomaterials for tarsal plate reconstruction and our innovative work

Large tarsal plate defect reconstruction is one of the most challenging tasks for plastic surgeons.Based on our practical work and literature review,the techniques and postoperative results of the preserved sclera,ear cartilage,and acellular dermal matrix(ADM)as tarsal plate substitutes were investigated.Two cases were reviewed.Case 1 was a 22-year-old female who had total loss of the right lower eyelid.Ear cartilage(23 mm25 mm)was implanted under the expanded skin during the forehead skin-expanding procedure to form a skin-cartilageexpander capsule compound structure for lower eyelid reconstruction.Case 2 was a 7-year-old boy with a unilateral divided nevus.The lid and conjunctiva of the lower eyelid were invaded.A piece of ADM(12 mm4 mm)was used to repair the tarsal plate defect(12 mm3 mm).The conjunctiva of ADM was covered by itself.An orbicularis oculi myocutaneous flap was used for anterior lamella reconstruction.In case 1,the compound tissue survived and supported the lower eyelid,the lid margin was clear,and the structure was complete over a 1-year follow-up.The aesthetic appearance of the eyelid improved after depilation.It is the first clinical research on the expander capsule as eyelid conjunctiva.In case 2,the conjunctiva completely covered the superior ADM,and the transplant merged with the surrounding tissues without complications after 5 months.The preserved sclera has the longest application history as a tarsal plate substitute.However,it should be preserved in an eye bank and transplanted with conjunctiva repair.Ear cartilage is an autologous tissue that requires conjunctival reconstruction.Our clinical practice was the first to prove the possibility of the expander capsule as eyelid conjunctiva.It is feasible to prefabricate the skin-tarsal conjunctiva complex during the skin expansion procedure.Allogeneic ADM is a common clinical material with advantages of good biological histocompatibility,supportive strength,conjunctivalization,and not requiring donor site surgery.Plastic surgeons are familiar with autologous ear cartilage and ADM,which are easy to obtain and treat.Both ear cartilage and ADM are expected to be the first-line choices in future studies.

Reconstructing seafloor age distributions in lost ocean basins

Reconstructions of past seafloor age make it possible to quantify how plate tectonic forces,surface heat flow,ocean basin volume and global sea level have varied through geological time.However,past ocean basins that have now been subducted cannot be uniquely reconstructed,and a significant challenge is how to explore a wide range of possible reconstructions.Here,we investigate possible distributions of seafloor ages from the late Paleozoic to present using published full-plate reconstructions and a new,efficient seafloor age reconstruction workflow,all developed using the open-source software GPlates.We test alternative reconstruction models and examine the influence of assumed spreading rates within the Panthalassa Ocean on the reconstructed history of mean seafloor age,oceanic heat flow,and the contribution of ocean basin volume to global sea level.The reconstructions suggest variations in mean seafloor age of~15 Myr during the late Paleozoic,similar to the amplitude of variations previously proposed for the Cretaceous to present.Our reconstructed oceanic age-area distributions are broadly compatible with a scenario in which the long-period fluctuations in global sea level since the late Paleozoic are largely driven by changes in mean seafloor age.Previous suggestions of a constant rate of seafloor production through time can be modelled using our workflow,but require that oceanic plates in the Paleozoic move slower than continents based on current reconstructions of continental motion,which is difficult to reconcile with geodynamic studies.

Earth’s tectonic and plate boundary evolution over 1.8 billion years

Understanding the intricate relationships between the solid Earth and its surface systems in deep time necessitates comprehensive full-plate tectonic reconstructions that include evolving plate boundaries and oceanic plates.In particular,a tectonic reconstruction that spans multiple supercontinent cycles is important to understand the long-term evolution of Earth’s interior,surface environments and mineral resources.Here,we present a new full-plate tectonic reconstruction from 1.8 Ga to present that combines and refines three published models:one full-plate tectonic model spanning 1 Ga to present and two continental-drift models focused on the late Paleoproterozoic to Mesoproterozoic eras.Our model is constrained by geological and geophysical data,and presented as a relative plate motion model in a paleomagnetic reference frame.The model encompasses three supercontinents,Nuna(Columbia),Rodinia,and Gondwana/Pangea,and more than two complete supercontinent cycles,covering
40%of the Earth’s history.Our refinements to the base models are focused on times before 1.0 Ga,with minor changes for the Neoproterozoic.For times between 1.8 Ga and 1.0 Ga,the root mean square speeds for all plates generally range between 4 cm/yr and 7 cm/yr(despite short-term fast motion around 1.1 Ga),which are kinematically consistent with post-Pangean plate tectonic constraints.The time span of the existence of Nuna is updated to between 1.6 Ga(1.65 Ga in the base model)and 1.46 Ga based on geological and paleomagnetic data.We follow the base models to leave Amazonia/West Africa separate from Nuna(as well as Western Australia,which only collides with the remnants of Nuna after initial break-up),and South China/India separate from Rodinia.Contrary to the concept of a“boring billion”,our model reveals a dynamic geological history between 1.8 Ga and 0.8 Ga,characterized by supercontinent assembly and breakup,and continuous accretion events.The model is publicly accessible,providing a framework for future refinements and facilitating deep time studies of Earth’s system.We suggest that the model can serve as a valuable working hypothesis,laying the groundwork for future hypothesis testing.