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<jats:p>The tectonic affinity and origins of the Jurassic, siliciclastic San Cayetano and Constancia formations exposed in western and central Cuba in the Caribbean region remain debated. The scarcity of modern geochronologic studies on these Cuban units hampers both sedimentary provenance and palinspastic reconstructions, resulting in Caribbean models that tend to oversimplify the formation of Cuba and correlate the Jurassic strata to various regions such as North America, South America, the Yucatán margin, or the conceptual Caribeana domain. Using laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS), we conducted a detailed detrital zircon (DZ) U-Pb provenance study of these Cuban siliciclastic strata that provides critical insights into understanding the formation of Cuba during the Early Jurassic rifting stages of Pangea. Results from 19 San Cayetano Formation samples show a dominant Oaxaquia (ca. 1 Ga) and Chiapas batholith (ca. 250 Ma) signature, while six Constancia samples display variable ca. 1 Ga and ca. 250 Ma grains. The Lower Cretaceous Polier Formation and the Paleocene Moncada Formation also display the same ca. 1 Ga and ca. 250 Ma signatures. After comparing these Cuban data with data from other regional DZ studies, we propose that that the San Cayetano and Constancia formations are correlative to the Todos Santos Formation located in the southwestern Yucatán region of Mexico. These Cuban units were predominantly deposited adjacent to the Chiapas batholith during the Early Jurassic in northwest−southeast-trending basins created by Pangean rifting. They were eventually sheared during eastward migration of the Caribbean plate and transported northward until they collided with the North American continent in the Paleogene. This DZ study provides new constraints on the tectonic provenance of western and central Cuba and improves plate tectonic reconstructions of the Caribbean.</jats:p>

<jats:p>The Jurassic igneous rocks on Sumatra Island are important for investigating the Mesotethyan evolution and regional correlation in Southeast Asia. This paper presents new laser ablation−multicollector−inductively coupled plasma−mass spectrometry zircon U-Pb-Hf geochronological and isotopic, whole-rock elemental, and Sr-Nd isotopic data for the newly identified Glebruk dolerite and andesite in North Sumatra. New zircon dating results suggest that these mafic−intermediate volcanic rocks, with ages of 150−146 Ma, were formed during the Late Jurassic. The Glebruk dolerite and andesite belong to the calc-alkaline series, are enriched in the light rare earth elements, and exhibit depletion in Nb, Ta, and Ti. Thus, they resemble arc-like volcanic rocks. They have low (87Sr/86Sr)i ratios of 0.7038−0.7048 and strong positive εNd(t) and εHf(t) values of +6.4 to +7.5 and +4.8 to +18.6, respectively. Their geochemical signatures suggest that these Late Jurassic volcanic rocks were derived from a depleted mantle wedge that was metasomatized by the slab-derived melts. The Glebruk volcanic rocks were formed in a continental arc setting in response to the Late Jurassic northward subduction of the Woyla Ocean beneath West Sumatra. Our results and regional geological observations suggest that the Mesotethyan subduction-related igneous rocks could extend from South Qiangtang through West Yunnan to North Sumatra. The Woyla Ocean could represent the southern extension of the Mesotethyan Ocean.</jats:p>

<jats:p>We developed Vp, Vs, Vp/Vs ratio, and Poisson’s ratio models of the uppermost crust (&amp;lt;4 km depth) from the eastern San Francisco (SF) Bay (California, USA) to near the Calaveras fault along a 15-km-long, linear profile. Upper crustal velocities are highly variable beneath, west, and well east of the Hayward fault. We observe eight notable features, from west to east: (1) Near San Francisco Bay, there is an ∼2-km-wide structure with high Vp/Vs ratios (up to 5) and Poisson’s ratios (up to 0.48) extending from the surface to the base of our model, which we suggest the structure is a near-vertical fault that lies along a straight-line projection between the Silver Creek fault to the south and the Point Richmond fault to the north. The structure may be part of an ∼90-km-long fault along the eastern SF Bay. (2) The western East Bay Plain, the lower lying area between the bay and the hills, includes up to 800 m of low-velocity sediments (Vp ∼1600−3000 m/s, Vs ∼500 m/s to ∼1000 m/s), underlain by higher velocity basement rocks (Vp ∼3000−5800 m/s; Vs ∼1000−1500 m/s). (3) Between ∼1 km and 3 km east of the Bay shoreline, sediments thin in a series of steps (likely faults) toward the Hayward fault. (4) Between ∼3 km west and ∼1 km east of the Hayward fault (at the East Chabot fault) at depths greater than 1 km, basement Vp (up to 6000 m/s) and Vs (up to 2800 m/s) are high, and Vp/Vs ratios (&amp;lt;2) and Poisson’s ratios (&amp;lt;0.3) are low, suggesting crystalline rocks. Furthermore, a near-vertical zone of low Vp/Vs ratios and Poisson’s ratios is between near-surface traces of the Hayward and East Chabot faults, likely corresponding to the San Leandro Gabbro of Ponce et al. (2003). (5) Eastward of the East Chabot fault in the upper 1.5 km, basement Vp (∼3000 m/s to ∼4200 m/s) and Vs (∼1200−2000 m/s) are lower than those west of the fault. (6) In the eastern Hayward/Oakland Hills, there are zones of laterally varying, high- and low-velocity (Vp ∼2500−3000 m/s) Jurassic−Cretaceous and Tertiary sediments in the shallow subsurface that likely extend much deeper than imaged. (7) Seismic energy that propagates westward from sources east of the Hayward fault (HF) appear weaker than energy that propagates eastward from sources west of the HF, suggesting that the HF acts as a partial barrier to shallow seismic energy propagation into the more populated eastern SF Bay area. (8) Unlike many fault zones, it appears that the active trace of the Hayward fault (in our study area) is not cored by a prominent, low-velocity zone relative to rocks to the east and west of the active trace. However, the active trace does mark a prominent change from relatively higher velocities to the west and lower velocities to the east.</jats:p>

<jats:p>The accretion of future allochthonous terranes (e.g., microcontinents or oceanic plateaus) onto the southern margin of Asia occurred repeatedly during the evolution and closure of the Tethyan oceanic realm, but the specific geodynamic processes of this protracted convergence, successive accretion, and subduction zone initiation remain largely unknown. Here, we use numerical models to better understand the dynamics that govern multiple terrane accretions and the polarity of new subduction zone initiation. Our results show that the sediments surrounding the future terranes and the structural complexity of the overriding plate are important factors that affect accretion of multiple plates and guide subduction polarity. Wide (≥400 km) and buoyant terranes with sediments behind them and fast continental plate motions are favorable for multiple unidirectional subduction zone jumps, which are also referred to as subduction zone transference, and successive terrane-accretion events. The jumping times (∼3−20+ m.y.) are mainly determined by the convergence rates and rheology of the overriding complex plate with preceding terrane collisions, which increase with slower convergence rates and/or a greater number of preceding terrane collisions. Our work provides new insights into the key geodynamic conditions governing multiple subduction zone jumps induced by successive accretion and discusses Tethyan evolution at a macro level. More than 50 m.y. after India-Asia collision, subduction has yet to initiate along the southern Indian plate, which may be the joint result of slower plate convergence and partitioned deformation across southern Asia.</jats:p>

<jats:p>The rhythmic evaporation cycle is an ideal recorder of astronomical cycle signals, but studies on cyclostratigraphy have yet to be directly conducted on halite-rich strata. The Qianjiang Depression of the Jianghan Basin is a representative Eocene East Asian halite-rich basin, and the salt rhythmites that developed therein are important recorders of climate evolution in East Asia. This study selected five wells for basin-scale cyclostratigraphy analysis, taking the Lower Qian 4 member of the Qianjiang Formation as the research object. This study found that the basinal salt lake facies were dominated by obliquity cycles, whereas the shallow-water deposits mainly recorded short eccentricity cycles. The study also found that s3−s6 obliquity cycles could be detected throughout the salt lake sedimentary record. Therefore, a stepwise astronomical tuning scheme was adopted. First, the target intervals in different sedimentary areas were preliminarily tuned to s3−s6 obliquity cycles, and stratigraphic correlation was performed. Then, the tuned data were further adjusted using obliquity cycles to reveal the impact of obliquity on the development of salt rhythmites and establish a floating astronomical time scale (ATS). Sedimentary noise models and pollen analysis further demonstrated that obliquity amplitude modulation cycles drove periodic changes in hydrology and climate. Based on the spatiotemporal distribution of salt rhythmite−rich strata in Paleogene East Asia, this study proposes that the development of rhythmic evaporites can reveal the existence of a monsoon-like climate. Astronomical influence was an important driving force for developing the middle Eocene East Asian monsoon.</jats:p>

<jats:p>The subduction and demise of an ocean plate are generally recognized as essential processes that result in the reworking and maturation of the continental crust. The northern Lhasa Terrane in central Tibet represents the forefront of the Lhasa-Qiangtang collision belt following the closure of the Bangong-Nujiang Ocean. Thus, it is a pivotal location to study the transition processes from oceanic lithosphere subduction to continental collision as well as pertinent crustal growth mechanisms. Here, we present zircon U-Pb dating, whole-rock major and trace element and Sr-Nd isotope, and zircon Hf isotope and trace element data of the Mendang igneous complex, Baingoin County, northern Lhasa Terrane. Geochronological results show that the granodiorites, trachydacites, and rhyolites in the Mendang igneous complex formed at ca. 122−116 Ma, 97 Ma, and 73 Ma, respectively. The Early Cretaceous granodiorite samples are peraluminous with high SiO2, Al2O3, and K2O contents, and moderate A/CNK (molar ratio of Al2O3/[CaO + Na2O + K2O]) values, which are similar to those of typical felsic peraluminous I-type granites. The granodiorites are characterized by enrichment in light rare earth elements and large ion lithophile elements (e.g., Rb) and depletion in high field strength elements (e.g., Nb, Ta). They also show the most enriched whole-rock Sr-Nd [(87Sr/86Sr)i = 0.7072−0.7078; εNd(t) = −7.60 to −5.08] and zircon Hf [εHf(t) = −4.46 to +1.02] isotope compositions, indicating that the Early Cretaceous granodiorites were likely derived from an ancient basement under a subduction setting. The trachydacites have uniform SiO2, high Al2O3, Sr contents, and Sr/Y values, and low Y and Yb contents, belonging to adakitic rocks. They show more depleted whole-rock Sr-Nd [(87Sr/86Sr)i = 0.7065−0.7066; εNd(t) = −0.56 to −0.22] and zircon Hf [εHf(t) = 4.36−7.84] isotopes than the granodiorites, suggesting that the trachydacites may have generated from partial melting of the juvenile thickened lower continental crust. The rhyolites have the highest SiO2 and K2O contents in the Mendang igneous complex, and significant depletion of Ba, Sr, Eu, P, and Ti. They have slighter more enriched whole-rock Nd [εNd(t) = −3.71 to −1.16] and zircon Hf [εHf(t) = 1.03−4.31] isotope compositions than the trachydacites. These features suggest that the rhyolites were highly fractionated products of the crustal melts. Whole-rock Sr-Nd and zircon Hf isotopes of the Mendang igneous complex show a kink trend from enrichment to depletion and then transfer to enrichment again, signifying an increased contribution of juvenile materials in the northern Lhasa Terrane toward progressively replacing the ancient lower crust and accumulating to newly formed crust. The estimated crustal thickness beneath the northern Lhasa Terrane shows a sharp increase from the Early to Late Cretaceous and peak at ca. 97 Ma, whereas it largely decreases in the Late Cretaceous. Integrated with previous studies, we propose that the formation of the Mendang igneous complex (122−73 Ma) elaborately documents the regional tectonic transition from oceanic lithosphere subduction to demise as well as continental crustal differentiation and maturation. The rollback and breakoff of the southward subducted Bangong-Nujiang oceanic slab in the Early Cretaceous initiated diverse magmatism in the northern Lhasa Terrane. During the early Late Cretaceous, the widespread adakitic and Mg-rich magmatism was attributed to the delamination of the thickened lithosphere following the final amalgamation of the Lhasa and Qiangtang Terranes. In the late Late Cretaceous, post-collisional extension induced the formation of the rhyolites in the northern Lhasa Terrane. The growth and destruction of the continental crust had certain tempos from the oceanic lithosphere subduction to continental post-collision stage.</jats:p>

<jats:p>Widely separated basalt lava-flow outcrops in north-central Oregon, USA, expose products of a single eruptive episode. A Pliocene lava flow, here informally termed the Tetherow basalt, issued from vents near Redmond, in the Deschutes basin of Oregon, as a plains-forming basalt now exposed in continuous outcrops northward for 60 km. A similar basalt crops out 47 km farther north, near Maupin, within what was then a slightly incised ancestral Deschutes River canyon. The northernmost outcrops of this lava flow lie on Fulton Ridge, in the Dalles basin, near the confluence of the Deschutes and Columbia Rivers. Complementary lines of evidence confirm these rocks are all from the same volcanic eruption. Outcrops in the Deschutes and Dalles basins are chemically similar high-titanium basalts, petrographically similar to each other and distinct from other lava flows in the area. Paleomagnetic directions from 11 scattered sites are similar and indistinguishable by various tests for a common mean. Three new 40Ar/39Ar ages indicate the Tetherow basalt eruption occurred between 5.5 Ma and 5.0 Ma, likely at ca. 5.2 Ma. The widely separated outcrops of this lava flow span 160−180 km along the ancestral Deschutes River and downstream Columbia River. The lava flow’s length and erupted volume of 15−20 km3 are extraordinarily large in a non-flood-basalt setting. This lava flow provides a datum with which to describe regional physiographic history, assess incision rates, and infer tectonic history. Spanning different depositional basins, the Tetherow basalt is a useful chronologic and stratigraphic marker bed.</jats:p>

<jats:p>Reconstructing the uplift process of the eastern Qiangtang terrane is crucial for understanding the growth model of the central Tibetan Plateau. However, due to the limited amount of data available, it is not well constrained. The Tanggula granitoid pluton is an outstanding geological feature in the eastern Qiangtang terrane, and thus could provide crucial constraints on its uplift history. We applied multiple thermochronologic systems over a broad temperature range, including apatite U-Pb, biotite and K-feldspar 40Ar/39Ar, apatite and zircon fission-track, and zircon (U-Th)/He, to study samples from the Tanggula granitoid pluton. The results exhibit the expected relative age order of these thermochronologic systems, with 242−238 Ma apatite U-Pb ages, 218−204 Ma biotite 40Ar/39Ar ages, 197−191 Ma K-feldspar 40Ar/39Ar ages, 94−81 Ma zircon fission-track ages, 70−58 Ma zircon (U-Th)/He ages, and 61−39 Ma apatite fission-track ages. Using these thermochronologic ages and thermal history modeling results, we reconstructed a comprehensive thermal history for the pluton, from which three rapid cooling phases were revealed. The earliest rapid cooling phase (220−180 Ma; ∼5.25 °C/m.y.) closely followed the emplacement of the Tanggula granitoid pluton, and thus is primarily an expression of natural cooling triggered by conduction with the surrounding rocks. In contrast, the rapid cooling during 100−60 Ma and since 20 Ma can be interpreted to represent intense exhumation, with corresponding exhumation of 5.0−6.0 km and 2.3−2.8 km, as well as an average exhumation rate of 0.125−0.150 mm/yr and 0.115−0.140 mm/yr, respectively. According to the thermal history, the earliest uplift in the Tanggula region could have been initiated as early as the Late Cretaceous. Using the published data, we determined that the onset of rapid uplift and exhumation in the entire eastern Qiangtang terrane had a northeastward, stepwise propagation process. The region within or around Anduo first experienced rapid uplift and exhumation that initiated during the late Early Cretaceous (ca. 130 Ma), the Tanggula region to the northeast experienced rapid uplift and exhumation that initiated during the Late Cretaceous (ca. 100 Ma), and the region farther to the northeast in Tuotuohe and Yushu−Nangqian experienced rapid uplift and exhumation that initiated in the late Paleocene (ca. 60 Ma). The northeastward stepwise uplift and exhumation in the eastern Qiangtang terrane was likely caused by the combined Lhasa−Qiangtang and India−Asia continental collisions.</jats:p>

<jats:p>The lower Frasnian (Upper Devonian) Maywood Formation records incision of valleys into lower Paleozoic bedrock in fluvial to estuarine settings in northern Wyoming and deposition in estuarine to marine environments in southern Montana (USA). A distinctive fossil assemblage of microconchids, plant compression fossils, fish fossils, and microspores represent fauna and flora that lived in, and adjacent to, salinity-stressed ecological niches in the upper reaches of the Maywood valleys. A similar fossil assemblage is recorded in older Devonian valley-fill deposits of the Lower Devonian Beartooth Butte Formation, indicating that valley incision and subsequent transgression, occurred repeatedly over a span of nearly 30 million years with organisms tracking the marine incursions into the valleys. The fossil charcoal in the Maywood Formation captures a record of fire in adjacent terrestrial ecosystems. The amount of dioxygen (O2) was thus above the fire window level (16% by volume) and might have been near modern levels in the earliest Late Devonian atmosphere.</jats:p> <jats:p>The nearshore deposits of the Maywood Formation are overlain by extensive shallow carbonate shelf strata of the Jefferson Formation, likely resulting from a global transgression in the earliest Frasnian. A paired positive and negative δ13Ccarbonate [carb] isotopic excursion in the Jefferson with a range of &amp;gt;6‰ is a signal of the globally recognized “punctata” Event. The unconformably overlying Madison Limestone is lower Carboniferous, except for a thin basal Upper Devonian unit with marine palynomorphs. The Madison regionally records eastward transgression and establishment of widespread marine deposition. It also contains two positive δ13Ccarb excursions (up to ∼7.5‰) that make up the mid-Tournaisian (= Kinderhookian−Osagean boundary) carbon isotope excursion (TICE/KOBE). These isotope data provide a framework for regional and global correlation of northern Rocky Mountain strata and an archive of environmental and evolutionary change during the middle−late Paleozoic transition.</jats:p>

<jats:p>High-silica granites are significant carriers of highly incompatible elements and are closely associated with mineralization of the rare metal beryllium. Thus, understanding their origin and evolution is of paramount importance for comprehending the evolution of the continental crust and enrichment processes of beryllium. This study presents zircon U-Pb ages, whole-rock major and trace element compositions, and Nd-Hf-O isotopic data for Early Cretaceous high-silica granite porphyries, monazite U-Pb ages and Nd isotopic data for beryllium-rich quartz veins, and whole-rock and apatite Nd isotopic data for Permian tuffs in the Dongshanwan W-Mo-Be deposit in the southern Great Xing’an Range, northeastern China. Our aim is to elucidate the link between mineralization and magmatism and to further our insight into the processes of crystal-melt separation and the mechanisms driving beryllium enrichment in granitic magmatic systems. Zircon U-Pb dating of the high-silica granite porphyry yields a weighted mean 206Pb/238U age of 141 ± 1 Ma, which is consistent with the age of hydrothermal monazite (ca. 140 Ma) from the beryllium-rich quartz veins. Hydrothermal monazite from the intra-granite porphyry quartz vein has positive εNd(t) values (+0.76 to +1.63) that overlap broadly with whole-rock Nd isotopic compositions of the host granite porphyry [εNd(t) = +1.24 to +1.61]. These characteristics indicate that the Dongshanwan beryllium mineralization was temporally and genetically associated with magmatic-hydrothermal activity of the Dongshanwan high-silica granite porphyries. Our systematic studies suggest that both the Dongshanwan high-silica granite porphyries and coeval Be-barren high-silica granites in the study area are high-K calc-alkaline I-type granites. They originated from a shared magmatic system and formed by the partial melting of a predominantly juvenile medium- to high-K basaltic crustal source, with a minor addition of old crustal components. Rayleigh fractionation modeling indicates that the granitic magma underwent a two-stage crystal-melt separation process. During the first stage, the fractional crystallization of a large proportion of plagioclase, in which beryllium is compatible, not only effectively inhibited beryllium enrichment in the differentiated melt, but also removed a large amount of Ca. During the second stage, minerals in which beryllium is incompatible dominated the fractionating assemblage owing to the low Ca contents in the magma, resulting in a surge in beryllium concentration in the differentiated melt. Our findings reveal that beryllium cannot be appreciably enriched in calc-alkaline granitic magmatic systems until plagioclase fractionation has substantially removed Ca from the system.</jats:p>