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Mafic microgranular enclaves (MMEs), commonly found in granitoid intrusions, can provide unique perspectives on the nature of magma sources and evolution, physicochemical properties of magmas, and geotectonic dynamic evolution. However, their origin and generation remain under debate. In this paper, the Cretaceous Tongkeng pluton with MME occurrence located in the Xiaojiang area of Zhejiang Province, SE China, was examined. Zircon U-Pb dating indicates that the gabbroic diorite, MMEs, and their host quartz diorite all crystallized at 107-106 Ma. All samples from the Tongkeng pluton show a comparable range of initial 87Sr/86Sr values (0.70746-0.70841), eNd(t) values (-4.9 to -2.9), and zircon eHf(t) values (-7.3 to -2.9) with the peak value of - 6 to - 4. In addition, Pb isotope compositions are fairly consistent. Petrology, geochemical and isotopic compositions, and geochemical modeling suggest that the gabbroic diorite, MMEs, and their host rock were cognate and their primary magma was derived from the mixing between a mantle-derived magma and a crustal magma. The "magma differentiation and convection" model, proposed in this paper to improve our understanding of the origin of the MMEs and their host rock, suggests that the gabbroic and quartz dioritic magmas were formed by cognate magma differentiation, and the MME magma is a portion of the gabbroic dioritic magma that is incorporated into and mingled with the quartz dioritic magma. Misjudgment in the origin and generation of MMEs leads to an erroneous understanding of mantle properties, the genesis of granitoids, and therefore, many other geological processes. Hence, caution is needed when considering the relationship between the host granitoid and its associated MMEs with similar chemical and isotopic compositions, particularly for those exposed in areas where mafic rocks are absent (or undiscovered). [ABSTRACT FROM AUTHOR]

The genesis of intermediate-felsic rocks and the implications for crustal growth are highly controversial. These issues are particularly relevant to large igneous provinces, which are one of the most effective methods of crustal generation. Mafic magmas, even those with continental marks, have been considered as the contribution from mantle to crust, whereas the intermediate-felsic series in large igneous provinces has uncertain implications for crustal growth due to uncertainty about their modes of generation. In this paper, we focus on the intermediate-felsic granitoids, i.e., Gushicun diorites and granites, in the Xiong’er large igneous province (ca. 1780–1750 Ma) through detailed study of their petrology, chronology, and geochemistry. Our new data show that both diorites and granites have the same emplacement age of ca. 1780 Ma and were synchronized with the Xiong’er large igneous province. The granitoids are characterized by enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., Li, Ba, and Rb) but depletion in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti). They have almost the same ΣREE (rare earth element) contents and TTi-Zircon (~850 °C), whole-rock Nd (εNd(t) from −8.24 to −5.76), zircon Hf (εHf(t) isotope ratios of −14 to −8 isotope ratios), and O-isotope compositions (average δ18O = 5.3‰). The fine-grained Gushicun diorites have low Sr/Nd (<10) and Eu/Sm (<0.3) but high Si/Al (>3.2) ratios and are similar to the basaltic andesites in the Xiong’er large igneous province, which suggests that the diorites are crystallization melts that differentiated along the liquid line of descent. The Rayleigh fractionation model based on the REE contents shows that the Gushicun diorites were formed by 40%–50% fractional crystallization of Xiong’er basaltic melts. The characteristics of high K2O (3.8–4.7 wt%) and Yb contents (4.0–6.5 ppm), low Sr/Y (1.4–3.3), and low metaluminous values (A/CNK = 0.8–1.1) of the Gushicun granites with mantle-like O-isotope values rule out the melting genesis of low K2O (<0.5 wt%) amphibolite and trondhjemite–tonalite–granodiorites (TTGs) of the surrounding Taihua Complex. The Gushicun granites show a geochemical affinity with andesites in the Xiong’er large igneous province. The alphaMELTs simulation based on the major elements argues against the partial melting of amphibolite and TTGs but supports the melting genesis of Xiong’er intermediate igneous rocks with low water contents (<1 wt%). These findings shed light on the formation of the felsic series in large igneous provinces, which remelted the previous mafic-intermediate rocks via underplating basaltic magmas. Despite having enriched Nd- and Hf-isotope features, the Gushicun diorites represent juvenile crust, while the granites were formed by the reworking of juvenile crust instead of ancient crust. This paper also suggests that radiogenic isotopic ratios cannot be reliably used to assess types of continental crust. [ABSTRACT FROM AUTHOR]

The article critiques the comments made by Landing et al. on their paper, emphasizing that their interpretation of Cambrian strata in the Caledonian Highlands is flawed and lacks scientific support. It also discusses the issues with forced lithostratigraphic frameworks, the inadequate correlation methods used by Landing et al., and the inaccuracies in their data and interpretations regarding the Cambrian geological record.

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 eNd(t) and eHf(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. [ABSTRACT FROM AUTHOR]

For sedinentary archives to be used as a record of hinterland evolution, the factors affecting the archive nust be known. In addition to tectonics, a nunber of factors, such as changes in clinate and paleodrainage, as well as the degree of diagenesis, influence basin sedinents. The Indus River delta-fan systen of South-Central Asia records a history of Hinalayan evolution, and both the onshore and offshore sedinentary repositories have been studied extensively to research orogenesis. However, a nunber of unknowns renain regarding this systen. This paper seeks to elucidate the paleodrainage of the Indus River, in particular when it took on its nodern drainage configuration with respect to conjoinnent of the nain Hinalayan (Punjabi) tributary systen with the Indus trunk river. We leverage the fact that the Punjabi tributary systen has a significantly different provenance signature than the nain trunk Indus River, draining nainly the Indian plate. Therefore, after the Punjabi tributary systen joined the Indus River, the proportion of Indian plate naterial in the repositories downstrean of the confluence should have been higher than in the upstrean repository. We conpared bulk Sr-Nd data and detrital zircon U-Pb data fron the Cenozoic upstrean peripheral foreland basin and downstrean Indus delta and Indus Fan repositories. We deternined that throughout Neogene tines, repositories below the confluence had a higher proportion of naterial fron the Indian plate than those above the confluence. Therefore, we conclude that the Indus River took on its current configuration, with the Punjabi tributary systen draining into the Indus trunk river in the Paleogene, early in the history of the orogen. The exact tine when the tributary systen joined the Indus should correlate with a shift to nore Indian plate input in the down-strean repositories only. While the upstrean repository records no change in Indian plate input fron Eocene to Neogene tines, a shift to increased naterial fron the Indian plate occurs at the Eocene-Oligocene boundary in the delta, but sonetine between 50 Ma and 40 Ma in the fan. Though further work is required to understand the discrepancy between the two downstrean repositories, we can conclude that the tributary systen joined the Indus trunk river at or before the start of the Oligocene. [ABSTRACT FROM AUTHOR]

Petrography, fluid-inclusion microthermometry, stable isotope analyses, and radiometric (206Pb/238U) dating of Upper Triassic dolostones, saddle dolomite, and quartz and calcite cements were used to constrain the timing and conditions of dolomitization and cementation in the context of the tectonic evolution of a basin in the northern United Arab Emirates. Dolomitization (ca. 152.4 Ma) and precipitation of saddle dolomite (ca. 146.8 Ma), calcite (ca. 144.6 Ma), and quartz cements are attributed to focused synrifting flow of hot basinal brines into grain-supported limestones in which permeability was enhanced by incursion of meteoric waters beneath a disconformity surface. Another calcite cement generation (ca. 99.7 Ma) was formed by flow of hot brines during tectonic compression related to the obduction of Oman ophiolites in the Late Cretaceous. Thus, this paper provides new insights into (1) stratigraphic controls on and timing of hydrothermal (hot basinal brines) dolomitization, (2) the origin of closely associated intraformational limestones and dolostones, and (3) linkages between diagenesis and thermochemical modifications of basinal brines during tectonic evolution of sedimentary basins. [ABSTRACT FROM AUTHOR]

This document provides supporting information for an article titled "Bacterial magnetofossil evidence for enhanced Pacific Ocean respired carbon storage during buildup of Antarctic glaciation." It includes details of materials and studied sites, magnetic and geochemical analytical methods, model configuration and boundary conditions for climate simulation experiments, sea-ice fraction simulation results, the age model adopted for the studied sites, parameters associated with components identified from isothermal remanent magnetization (IRM) unmixing analysis, and the BH/BS ratio from TEM results and IRM unmixing. The study collected sediment samples from two sites in the eastern equatorial Pacific Ocean to trace deep Pacific Ocean deoxygenation and its relation to Southern Ocean production variations. Magnetic and geochemical measurements were performed to analyze the sediment samples. This document provides information on sediment ages and climate simulation experiments. Sediment ages were determined using a revised age model, and various fluxes were calculated based on the mass accumulation rate. Climate simulations were conducted using the Community Earth System Model, which consists of multiple components that interact with each other. The simulations were based on the climate state at 35 million years ago and included factors such as vegetation distribution, orbital conditions, and CO2 concentrations. The document also includes figures and tables with additional data and results. The given text appears to be a compilation of data tables and references related to various scientific studies and research papers. The tables include numerical values and ratios related to different samples and measurements. The references provide sources for further reading [Extracted from the article]

The Klamath Mountains Province of Northern California and southern Oregon, USA, consists of generally east-dipping terranes assembled via Paleozoic to Mesozoic subduction along the western margin of North America. The Klamath Mountains Province more than doubled in mass from Middle Jurassic to Early Cretaceous time, due to alternating episodes of extension (e.g., rifting and formation of the Josephine ophiolite) and shortening (e.g., Siskiyou and Nevadan events). However, the tectonic mechanisms driving this profound Mesozoic growth of the Klamath Mountains Province are poorly understood. In this paper, we show that formation of the Condrey Mountain schist (CMS) of the central Klamath Mountains Province spanned this critical time period and use the archive contained within the CMS as a key to deciphering the Mesozoic tectonics of the Klamath Mountains Province. Igneous samples from the outer CMS subunit yield U-Pb zircon ages of ca. 175–170 Ma, which reflect volcanic protolith eruptive timing. One detrital sample from the same subunit contains abundant (~54% of zircon grains analyzed) Middle Jurassic ages with Paleozoic and Proterozoic grains comprising the remainder and yields a maximum depositional age (MDA) of ca. 170 Ma. These ages, in the context of lithologic and thermochronologic relations, suggest that outer CMS protoliths accumulated in an outboard rift basin and subsequently underthrust the Klamath Mountains Province during the Late Jurassic Nevadan orogeny. Five samples of the chiefly metasedimentary inner CMS yield MDAs ranging from 160 Ma to 130 Ma, with younger ages corresponding to deeper structural levels. Such inverted age zonation is common in subduction complexes and, considering existing K-Ar ages, suggests that the inner CMS was assembled by progressive underplating over a >10 m.y. timespan. Despite this age zonation, age spectra derived from structurally shallow and deep portions of the inner CMS closely overlap those derived from the oldest section of the Franciscan subduction complex (South Fork Mountain schist). These relations suggest that the inner CMS is a composite of South Fork Mountain schist slices that were sequentially underplated beneath the Klamath Mountains Province. The age, inboard position, and structural position (i.e., the CMS resides directly beneath Jurassic arc assemblages with no intervening mantle) of the CMS suggest that these rocks were emplaced during one or more previously unrecognized episodes of shallow-angle subduction restricted to the Klamath Mountains Province. Furthermore, emplacement of the deepest portions of the CMS corresponds with the ca. 136 Ma termination of magmatism in the Klamath Mountains Province, which we relate to the disruption of asthenospheric flow during slab shallowing. The timing of shallow-angle subduction shortly precedes that of the westward translation of the Klamath Mountains Province relative to correlative rocks in the northern Sierra Nevada Range, which suggests that subduction dynamics were responsible for relocating the Klamath Mountains Province from the arc to the forearc. In aggregate, the above relations require at least three distinct phases of extension and/or rifting, each followed by an episode of shallow-angle underthrusting. The dynamic upper-plate deformation envisioned here is best interpreted in the context of tectonic switching, whereby slab steepening and trench retreat alternate with slab shallowing due to recurrent subduction of buoyant oceanic features [ABSTRACT FROM AUTHOR]

Comprehensive U-Pb detrital zircon geochronology of Ediacaran sandstones from Oman indicates that they originated from Neoproterozoic basement with a peak magmatic age of ca. 850-780 Ma (Tonian), with lesser Paleoproterozoic and Ediacaran sources and renewed magmatic input starting at ca. 550 Ma. Comparison with detrital zircons from the Arabian-Nubian and NW Indian Shields supports an eastern Gondwana affinity for the Ediacaran succession of Oman. Tonian basement sediment sources are present in Oman. Sources for older Paleoproterozoic zircons (ca. 2500 and 1800 Ma) are not found in Oman but are known from the cratonic Indian Shield. The signal of the main magmatic events of the juvenile Arabian-Nubian Shield, peaking at ca. 640-620 Ma, is rare or absent in the Ediacaran rock succession of Oman. However, deformed Ediacaran clastic units with an Arabian-Nubian Shield affinity occur in western Oman. Influx of latest Ediacaran-early Cambrian zircons (550-525 Ma) is interpreted as due to final Cambrian Angudan/Malagasy orogeny-related magmatism. These results, together with new ages for volcano-sedimentary terranes in the subsurface of SW Oman and seismic observations, support the interpretation that the Ediacaran succession of Oman was deposited along the western, passive margin of the Greater Indian Shield, on the eastern (east and west in this paper refer to present-day coordinates) side of the Mozambique Ocean. Oman then collided with the Arabian-Nubian Shield in the early Cambrian, when the Angudan/Malagasy orogeny led to final consolidation of Gondwana. Our data support the inference that the youngest and final suture between the Indian and Arabian Shields lies in the subsurface of Oman along the early Cambrian western deformation front. [ABSTRACT FROM AUTHOR]

Water is known to play a crucial role in the generation of many large igneous provinces (LIP) worldwide, but the amount and origin of the water in their sources is still under debate. To address this question, this paper presents in situ major-, trace-element, and Sr isotope data coupled with bulk-mineral O-HHe isotope analyses of amphibole in a suite of aillikites from the Tarim LIP (NW China). The cores of zoned macrocrysts and microcrysts display partially overlapping compositions ranging between edenite and pargasite (75-83 versus 75-80 Mg#), which suggest a common origin from an evolving magma. The rims (Mg# = 75-80) of both macrocrysts and microcrysts are very similar to their cores for many elements, except for higher Sr and Ba contents. All the amphibole zones show similar primitive mantle-normalized trace element patterns, suggesting that they crystallized at different stages during magmatic evolution. This interpretation is confirmed by the homogenous Sr isotope compositions (87Sr/86Sr(i) = 0.70298-0.70394) of these amphiboles, which overlap with those of magmatic apatites and perovskites in these aillikites. The hydrogen isotope compositions (-D = -120‰ to -140‰) of the amphiboles are significantly lower than average mantle values. Given the low water contents (<0.66 wt%) of these minerals, the low H iso signatures of the amphiboles might be caused by variable H2O loss during magma ascent. However, open-system Rayleigh fractionation modeling suggests that the hydrogen isotope compositions of these amphibole phenocrysts cannot be fully reproduced by crystallization following magmatic degassing. These low Î'D values require incorporation of recycled altered oceanic crust containing hydrous components in the plume source of these aillikites, which is consistent with the previously published moderately radiogenic He isotope ratios of olivine separates and bulk-rock Os and Pb isotope data for these same samples. We conclude that water in these magmas was derived from a plume source containing recycled water-bearing oceanic crust. [ABSTRACT FROM AUTHOR]

In this paper, we report on a biostratigraphic, magnetostratigraphic, and stable isotope (δ13C and 3He) analysis across three pelagic limestone sections of the Campanian Scaglia Rossa Formation exposed in the classic Bottaccione Gorge at Gubbio (Umbria region), near the village of Furlo, and near the town of Apiro (both in the Marche region), all located in the Umbria-Marche basin of the northeastern Apennines of central Italy. These sections record the coincidental occurrence of an extraterrestrial 3He (3HeET) anomaly known as K1 and a negative shift in the δ13C record known as the early Campanian event. Cyclostratigraphic spectral analysis of the Furlo section based on a highresolution magnetic susceptibility record in these pelagic limestones revealed that the regular orbitally forced Milankovitch cycles are somewhat disturbed or blurred through the interval of the coincident 3HeET K1 anomaly and the early Campanian event isotopic anomaly, suggesting a causal effect resulting from the enhanced influx of extraterrestrial material (i.e., interplanetary dust particles and a myriad of small meteorite impacts). This would have altered the transparency of the atmosphere, causing a short-lived climate change event. [ABSTRACT FROM AUTHOR]

Stream-terrace morphostratigraphy and optically stimulated luminescence (OSL) geochronology indicate that storm-driven sedimentation has caused down-system decoupling of the uppermost reaches of McMillan Creek (southern California, USA) from the lower reaches of McMillan Creek since 1960 ± 190 yr B.P. This is significant because source-to-sink studies report high degrees of sediment transport connectivity over millennial time scales during periods of high fluvial discharge in sediment routing systems. The most recent relatively large-magnitude episode of sedimentation emplaced a sediment slug in the ephemeral channel of McMillan Creek. The sediment slug is correlated to the "California Storm of January 1862" via OSL dating. In this paper, a conceptual model of sediment slug dynamics in an ephemeral stream over 16 decades is developed based on fluvial sedimentation events that in most instances included reworking slug-derived sediment. Due to the episodic nature of streamflow in ephemeral streams and the dearth of sediment transport between streamflow events, sediment slug coherency is sustained over longer periods of time in ephemeral streams than in perennial streams having steady or variable flow regimes. The longevity of sediment-slug coherency in ephemeral streams leads to more prolonged down-system decoupling in sediment routing systems than down-system decoupling caused by ordinary fluvial sedimentation. In McMillan Creek, it is possible that up-system decoupling driven by sedimentation has been contemporaneous with down-system decoupling, but factors other than sedimentation may have a more significant role in up-system decoupling. Source-to-sink studies completed in areas having a Mediterranean climate cannot assume that sediment flux out of upland source areas includes the total amount of sediment available for transport. [ABSTRACT FROM AUTHOR]

Understanding of the geodynamic evolution of the Tethyan realm cannot be complete without paleogeographical reconstructions of the North Qiangtang Block (NQB) that occupies a central position in Tibet. However, the reliability of such a reconstruction for the Paleozoic still requires substantial improvement. In this paper, we present paleomagnetic results obtained from the Middle Permian limestones and Upper Permian volcanic rocks in the Tanggula area, aiming to provide precise constraints on the NQB kinematics during the geodynamic evolution of the Tethys realm. Combined with other available paleomagnetic data from the NQB, our results suggest that the block was stably located at ~24°S for a long time before the Middle Permian, started to drift rapidly northward in the Middle Permian, and reached ~8.4°S in the Late Permian. The NQB continued drifting rapidly northward during the Triassic until merging with the southern margin of Eurasia in the Late Triassic. We reviewed new and available paleomagnetic and geological data and proposed a revised model for the tectonic evolution of the eastern Tethys realm. The NQB likely belonged to a ribbon-like separate continental archipelago in the middle of the Paleo-Tethys Ocean during the early--late Paleozoic. The Cimmerian continent, including the South Qiangtang Block (SQB), rifted away from the northern margin of Gondwana and drifted northward to ~22°S in the Middle Permian. The continent approached or partially collided with the NQB, resulting in the rapid northward movement of the NQB and the formation of the Longmuco--Shuanghu suture between the NQB and SQB. [ABSTRACT FROM AUTHOR]

A transfer zone is a kind of structure that is produced to conserve deformation of a fault structure on both sides. Increasing numbers of transfer zones are being identified in rift basins, which are areas of petroleum accumulation and potential exploration targets. This paper provides a numerical simulation method for the genesis and development of transfer zones based on geomechanical modeling. On the basis of three-dimensional (3-D) seismic interpretation, using the Tongcheng fault as an example, the fault activity parameter and fault activity intensity index were established to quantitatively characterize the difference in fault activity on the two sides of a transfer zone. A geomechanical model was developed for a transfer zone in a rift basin, and the structural characteristics and genetic mechanism of a convergent fault were studied using paleostress and strain numerical simulations. Affected by different movements of boundary faults and basement faults, the evolution of the Tongcheng fault can be divided into three stages: (1) during the Funing period, which was the main development period of compound transfer faults, the activity, stress, and strain of the fault blocks on either side of the Tongcheng fault were obviously different; (2) during the Dainan period, which was the development stage of inherited compound transfer faults, the northern part of the Tongcheng area underwent local compression, and the T3 anticline began to form; and (3) during the Sanduo period, the Tongcheng fault experienced right-lateral strike-slip activity, where the activity showed two stages of change, first increasing and then decreasing, and the Tongcheng fault anticline developed. The superposition of multiple complex tectonic movements produced a transfer zone that has both strike-slip and extensional fault properties. The geomechanical model in this paper provides important insights for analyzing the evolution of transfer zones in rift basins. [ABSTRACT FROM AUTHOR]

As one of the major Archean microcontinental blocks in the North China craton, the Yinshan block consists of the Guyang granite-greenstone belt and the Wuchuan high-grade complex, both of which preserve large volumes of Neoarchean tonalitic-trondhjemitic-granodioritic (TTG) gneisses. The petrogenesis and tectonic setting of these TTG gneisses are of great significance to understanding the Neoarchean crustal growth and evolution of the Yinshan block. Although extensive investigations have been carried out on the TTG gneisses in the Yinshan block, controversy remains regarding their petrogenesis and tectonic setting. In this study, we present new geochronological, geochemical, and Sr-Nd-Pb-Hf isotopic data for the Neoarchean TTG gneisses in the Xiwulanbulang area from the Wuchuan high-grade complex. Laser ablation–inductively coupled plasma–mass spectrometry zircon U-Pb dating results from six TTG gneissic samples show that their igneous TTG plutons were emplaced in the period 2.61–2.48 Ga. The results from zircon Lu-Hf isotopes show that εHf(t) values (–3.2 to +7.5) and depleted mantle model ages (3270–2651 Ma) are like those of the oldest trondhjemite (ca. 2.7 Ga) exposed in the Xiwulanbulang area, indicating that it mainly resulted from partial melting of 2.7 Ga juvenile mafic crust. Geochemically, the Xiwulanbulang TTG gneisses contain high Sr (280–800 ppm) contents, low Y (1.05–9.54 ppm) and Yb (0.05–0.90 ppm) contents, and relatively high LaN/YbN (12.8–105) and Sr/Y (39.91–1392.6 ppm) ratios, with relative enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs), showing the characteristics of adakitic rocks. In addition, their lower contents of MgO, Ni, Cr, and Mg# indicate that the Xiwulanbulang TTG rocks belong to adakite sourced from thickened continental lower crust. Also, the TTG gneisses show similar initial 87Sr/86Sr ratios (0.701659–0.702635) and εNd(t) values (−4.37 to + 3.55), with 206Pb/204Pb(t) = 13.910485–15.241164, 207Pb/204Pb(t) = 14.806723–15.259938, and 208Pb/204Pb(t) = 33.758621–35.592727, suggesting a depleted mantle source modified with some enriched components. Collectively, the Xiwulanbulang TTG rocks were most likely derived from the partial melting of thickened mafic crust between 2.61 and 2.48 Ga. Combining previous studies with data presented in this paper, we propose that the Yinshan block underwent two major igneous events during Neoarchean time, with the earlier one occurring ca. 2.7 Ga, forming a thickened mafic crust and minor TTG rocks, and the second igneous event at 2.61–2.48 Ga, resulting in the partial melting of the ca. 2.7 Ga continental lower (mafic) crust to form the TTG plutons. The geochemical data for the Xiwulanbulang TTG gneisses are inconsistent with a model for the partial melting of subducted slabs, but combined with other geologic considerations, a model in which the partial melting of a thickened continental lower (mafic) crust was heated by a mantle plume is favored for the formation of these Neoarchean TTG rocks in the Yinshan block. [ABSTRACT FROM AUTHOR]

The Central Andes are unique in the global system of subduction zones in that a significant, high-altitude plateau has formed above a subduction zone. In this region, both subduction and the associated magmatism have been shown to vary in both space and time. Geophysical data have been invaluable in determining the subsurface structure of this region. Extensive seismic studies have determined the regional-scale distribution of partial melt in the crust and upper mantle. Magnetotelluric studies have been effective in providing independent constraints on the quantity and composition of partial melt in the crust and upper mantle. Geodetic studies have shown that a small number of volcanic centers exhibit persistent, long-term uplift that may indicate the formation of plutons or future eruptions. This paper describes a detailed study of the Southern Puna using magnetotelluric (MT) data. This region is located at the southern limit of the Central Andes in a region where a recent transition from flat-slab subduction to normal subduction has caused an increase in magmatism, in addition to hypothesized lithospheric delamination. It is also a region where an extensive zone adjacent to the volcanic arc is undergoing surface uplift, located near Volcán Lastarria and Cordon del Azufre (collectively called Lazufre). The main goals of the work are to define the crustal structure and to investigate processes that may cause surface uplift of relatively large regions not associated with active volcanism. As part of the PLUTONS project, MT data were collected on an east-west transect (approximately along 25°S) that extended across the Southern Puna, from Lazufre to north of Cerro Galan. The data were combined with previously collected MT data around Lazufre and inverted to give a 3-D resistivity model of the crust. The low resistivity of the crust resulted in limited sensitivity to mantle structure. A number of major crustal conductors were detected and included (1) a mid-crustal conductor extending eastward from the volcanic arc as far as the Salar de Antofalla; (2) an upper- to mid-crustal conductor located north of Cerro Galan; and (3) a conductor that rises westward from (1) and terminates directly beneath the region of surface uplift at Lazufre. These conductors are broadly coincident with the location of crustal low shear-wave anomalies. The conductive features were interpreted to be due to zones of partial melt stored in the crust, and petrological data were used to estimate melt fractions. Below Lazufre, it is likely that aqueous fluids contribute to the high conductivity, which is observed within the depth range of the inflation source, giving evidence that the surface uplift may be associated with both magmatic and hydrothermal processes. [ABSTRACT FROM AUTHOR]

We reject the notion of a Jurassic continental arc in eastern Mexico, termed the "Nazas arc," on geologic grounds. Instead, we propose that the Jurassic continental arc of the SW Cordilleran U.S. and northern Sonora, Mexico, passed southward into the oceanic realm and is represented by Jurassic arc volcanic and plutonic rocks that fringed the Mexican paleo-Pacific margin, which are currently found in the western Peninsular Ranges of southern California, USA, and Baja California, the Vizcaino Peninsula of Baja California, and western mainland Mexico. To show this, we present a summary of the geologic features of a continental arc, using the geology of the southern end of the Jurassic continental arc, in southern Arizona and northern Sonora. These features include multi-kilometer--thick sections of volcanic rock; large volcanic centers, including silicic calderas; major eruptive units that can be correlated for distances of 100 km or more; abundant, large plutonic suites; and continuity of these features for distances of hundreds of kilometers along the length of the continental arc. Then we show that the "Nazas arc" consists of scattered, small continental rift basins with thin (meters to tens of meters thick) volcanic sections at the base of clastic sections that are hundreds of meters thick. Plutonic rocks are entirely absent from the "Nazas arc," despite the fact that post-Jurassic tectonic events should have exposed them if they existed. This paper also presents a tabulation of all published U-Pb zircon dates in the Jurassic continental arc of southern Arizona, USA, and northern Sonora (Table 1A), and in the "Nazas arc" of eastern Mexico (Table 1B), with ages, methods, the rock type dated, and notes on geologic relations. We use this to detail the abundance of thick, laterally extensive volcanic sections and large plutonic suites in a continental arc (the Jurassic arc of southern Arizona--northern Sonora), which contrasts sharply with the "Nazas arc." The term "Nazas arc" has been in widespread usage for volcanic rocks in eastern Mexico for decades in many dozens of papers, and it is portrayed as a 2000-km-long, 250-km-wide belt that extends from Sonora through eastern Mexico to Chiapas. It has been misunderstood to form a subduction- related silicic large igneous province (SLIP), and it has been proposed that the Gulf of Mexico formed as a back-arc basin behind the "Nazas arc." The "Nazas arc" model also requires an east-dipping subduction zone under Mexico, and a separate west-dipping subduction zone under the oceanic arc rocks of western Mexico, which those models portray as an exotic arc, despite the presence of abundant detrital zircon from the Mexican margin. We urge workers to abandon the term "Nazas arc" and replace it with "Nazas rift province," which represents continental rift basins formed during the breakup of Pangea. [ABSTRACT FROM AUTHOR]

Arc magmas globally are H2O-Cl-S-rich and moderately oxidized (ΔFMQ = +1 to +2) relative to most other mantle-derived magmas (ΔFMQ = 0). Their relatively high oxidation state limits the extent to which sulfide phases separate from the magma, which would otherwise tend to deplete the melt in chalcophile elements such as Cu (highly siderophile elements such as Au and especially platinum-group elements are depleted by even small amounts of sulfide segregation). As these magmas rise into the crust and begin to crystallize, they will reach volatile saturation, and a hydrous, saline, S-rich, moderately oxidized fluid is released, into which chalcophile and any remaining siderophile metals (as well as many other water-soluble elements) will strongly partition. This magmatichydrothermal fluid phase has the potential to form ore deposits (most commonly porphyry Cu ± Mo ± Au deposits) if its metal load is precipitated in economic concentrations, but there are many steps along the way that must be successfully negotiated before this can occur. This paper seeks to identify the main steps along the path from magma genesis to hydrothermal mineral precipitation that affect the chances of forming an ore deposit (defined as an economically mineable resource) and attempts to estimate the probability of achieving each step. The cumulative probability of forming a large porphyry Cu deposit at any given time in an arc magmatic system (i.e., a single batholith-linked volcanoplutonic complex) is estimated to be ~0.001%, and less than 1/10 of these deposits will be uplifted and exposed at shallow enough depths to mine economically (0.0001%). Continued uplift and erosion in active convergent tectonic regimes rapidly remove these upper-crustal deposits from the geological record, such that the probability of finding them in older arc systems decreases further with age, to the point that porphyry Cu deposits are almost nonexistent in Precambrian rocks. A key finding of this paper is that most volcanoplutonic arcs above subduction zones are prospective for porphyry ore formation, with probabilities only falling to low values at late stages of magmatic-hydrothermal fluid exsolution, focusing, and metal deposition. This is in part because of the high threshold required in terms of grade and tonnage for a deposit to be considered economic. Thus, the probability of forming a porphyry-type system in any given arc segment is relatively high, but the probability that it will be a large economic deposit is low, dictated to a large extent by mineral economics and metal prices. [ABSTRACT FROM AUTHOR]

Thermal springs in the southeastern Canadian Cordillera occur in association with several major fault zones, which may permit deep circulation of fluid through fractured reservoirs to depths greater than 2 km. Both the current stress field and the most recent kinematics of these faults likely play a significant role in localizing hydrothermal upwellings but are poorly resolved. In this paper, we present new data from structural mapping along the Columbia River, Slocan Lake, Purcell Trench, Southern Rocky Mountain Trench, and Redwall faults. Fault plane and slickenfiber orientations measured in the field indicate a previously unidentified, post-Eocene phase of dextral strike-slip kinematics on these faults, which have historically been mapped primarily as Eocene extensional structures. The NE--SW maximum principal stress required for these kinematics shares a similar orientation to the present-day stress field derived from crustal earthquake focal mechanisms, which suggests dextral slip may be a recent and ongoing development that continues at the present time. On a regional scale, there is a positive correlation between the locations of springs and regions with elevated seismicity. At the local scale, geothermal upwellings may be controlled by local zones of enhanced permeability including fault intersections and strain-transfer zones. The identification of favorable structural settings may enable discovery of hidden (a.k.a. blind) geothermal energy resources. [ABSTRACT FROM AUTHOR]

Subduction initiation is a pivotal process in plate tectonics. Models of subduction initiation include the collapse of passive margins, oceanic transform faults, inversion of oceanic core complexes, and ridge failure but have ignored the potential effects of continental crust relicts within the oceanic crust. In this paper, we explore the role of microcontinents on subduction initiation through two-dimensional thermo-mechanical numerical modeling. We consider three scenarios with variable ages of oceanic crust surrounding the microcon-tinent and parametrically examine the microcontinent characteristics (size, crustal thickness, thermal gradient, and rheology), oceanic plate age, and convergence rates. Results suggest that moderate-size (≥300 km) microcontinents can nucleate subduction initiation at the junction between continental and oceanic plates. A large part of the microcontinent would be dragged into the subduction zone, and the subsequent asthenosphere upwellings would incorporate part of the microcontinent. Our numerical models add a new hypothetical scenario for subduction initiation, especially for those places where a young and buoyant plate subducts beneath an older and denser oceanic plate. Moreover, they can explain the origin of exotic crust materials and ultrahigh-pressure minerals in supra-subduction zone ophiolites. [ABSTRACT FROM AUTHOR]

The development and application of luminescence dating and dosimetry techniques have grown exponentially in the last several decades. Luminescence methods provide age control for a broad range of geological and archaeological contexts and can characterize mineral and glass properties linked to geologic origin, Earth-surface processes, and past exposure to light, heat, and ionizing radiation. The applicable age range for luminescence methods spans the last 500,000 years or more, which covers the period of modern human evolution, and provides context for rates and magnitudes of geological processes, hazards, and climate change. Given the growth in applications and publications of luminescence data, there is a need for unified, community-driven guidance regarding the publication and interpretation of luminescence results. This paper presents a guide to the essential information necessary for publishing and archiving luminescence ages as well as supporting data that is transportable and expandable for different research objectives and publication outlets. We outline the information needed for the interpretation of luminescence data sets, including data associated with equivalent dose, dose rate, age models, and stratigraphic context. A brief review of the fundamentals of luminescence techniques and applications, including guidance on sample collection and insight into laboratory processing and analysis steps, is presented to provide context for publishing and data archiving. [ABSTRACT FROM AUTHOR]

The near-source, multistream, and rapidly changing sedimentary environments of conglomerate reservoirs lead to reservoir characteristics such as strong heterogeneity and complex modal pore structure, which create unique seepage pathways and strong permeability anisotropy, which in turn affect the displacement mode and oil recovery of crude oil in pores and throats. Thus, it is necessary to clarify the genetic mechanism and controlling factors of this permeability anisotropy, providing the basis and premise of sustainable and efficient development of conglomerate reservoirs. In this paper, a typical conglomerate reservoir from the Kexia Formation in the 7th Block of the Karamay oilfield (Xinjiang, China) was selected as the research object to solve the permeability anisotropy problem. According to the sealed coring data, eight conglomerate samples were cut preliminarily in the field and prepared finely in the laboratory to make standard cube samples with side lengths of 4.5 cm, and then these samples were investigated using casting thin section, computed tomography scanning, and constant velocity mercury injection experimental methods to determine the genetic mechanism of permeability anisotropy and its controlling factors at macro- and microscales. The results showed that sedimentation and hydrodynamic conditions controlled the distribution of permeability anisotropy, the separation, rounding, and arrangement of mineral particles, the development of sedimentary structural planes, and the different types of packing textures, which affected the seepage paths and resistance in different directions, resulting in great differences in permeability anisotropy. The permeability in the direction parallel to water flow was the largest, followed by the direction perpendicular to water flow, and the permeability in the vertical sedimentation direction was the lowest because of the combined influences of the tortuosity of seepage, the connectivity of pore throats, and the sedimentary structural planes. In addition, diagenesis in later stages can reduce the absolute value of permeability in different directions and the strength of permeability anisotropy by changing the micropore structure of the conglomerate reservoir, but it will not change the distribution of permeability anisotropy. Based on these observations, a generalized linear mixed model was used to analyze the micropore structure parameters and standard deviation of permeability in different directions from the eight conglomerate samples, and the results showed that the relative sorting coefficient had the greatest influence on the standard deviation of permeability, and the uniformity of pore-throat size distribution was the main microscale controlling factor on the strength of permeability anisotropy. When the pore-throat size distribution was less uniform, the difference in the amplitude of permeability anisotropy was more obvious. The average capillary radius, seepage tortuosity, and maximum pore-throat radius showed less importance than relative sorting coefficient, so they are considered secondary factors. The other micropore structure parameters showed some influence on the permeability anisotropy, but the degree of influence was limited. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing technology is relatively mature in North America, but under complex geological conditions, such as those in China, the application of this technology still faces great challenges. At present, techniques for the numerical simulation of hydraulic fracture networks are mainly based on the prediction of the fracture half-height and half-length, which cannot capture the heterogeneity of continental low-permeability sandstone reservoirs in China and the distribution of the asymmetric hydraulic fracture network present in them. Therefore, determining the asymmetric propagation mechanism of hydraulic fracture networks is very important for improving the recovery rates of continental reservoirs. In this paper, taking the Ordos Basin in China as an example, the spatial distribution of the stress field of a heterogeneous continental reservoir is precisely predicted by reservoir mechanical heterogeneity modeling. By using a microseismic monitoring method, the 3-D morphology of the hydraulic fracture network is determined. Through the coupling of multisource data, the frequency distributions of the determined in situ stress magnitudes in different hydraulic fracturing stages are obtained. The propagation direction of the hydraulic fracture network changes under the control of the horizontal stress difference (Δs) and the presence of natural fractures. The smaller Δs is, the greater the deflection of the hydraulic fracture propagation direction. The asymmetric propagation of these fractures is related to the frequency distribution of Δs. As the frequency of Δs approaches a normal distribution, the two wings of the hydraulic fracture network become basically equal in length, and as Δs deviates more from a normal distribution, the difference between the two wings of the hydraulic fracture network increases. These research results will provide new insight for modeling, exploring, and developing continental reservoirs. [ABSTRACT FROM AUTHOR]

This paper presents a detailed field characterization of boudinage in a high- strain zone several kilometers wide in Northern China to establish relationships between boudin types and rheological contrasts between different parts of migmatites during the migmatization process. This zone contains nearly all types of boudins: foliation boudins, block- torn boudins, pinch- and- swell structures, tapering boudins, object boudins, and modified boudins. These boudinage structures record the different stages of meltinvolved and solid- state deformation. The boudinage of migmatites is significantly controlled by the evolving rheological contrasts between the leucosome and melanosome. During the melting stage, the deformation and boudinage of rocks are controlled by the melt fraction. Migmatite strength progressively decreases with increasing melt fraction. The occurrence of melt- filled foliation boudins and melanosome block boudins suggests that the residuum and melanosome are more competent than the leucosome. During solid- state deformation after crystallization, the existence of recrystallized solid- state leucosomes and the intrusion of pegmatites cause the migmatite strength to increase. The relationship is reversed: the leucosome is much more competent than the melanosome. The type and geometry of boudins and pinch- and- swell structures are correlated to the fraction of leucosome in the migmatites. The mechanical strength and strain localization of migmatites after crystallization depend on the presence and volume fraction of the different mineral phases, as well as the mineral grain size. The type and geometry of boudins suggest that the effective viscosity of migmatite can be ranked, from high to low, as: quartz veins; coarse- grained, thick pegmatite; coarse- grained, diatexite migmatite; medium- grained leucosome; and fine- grained melanosome. While experiencing partial melting and migmatization, a rheologically homogeneous protolith is turned into two dominant lithologic domains: a competent diatexite migmatite domain and an incompetent melanosome migmatite domain. Spatially, with the increasing leucosome fraction in migmatites, the migmatite rheology of rock changes from homogeneous to heterogeneous and anisotropic, and then back to homogeneous. The strain distribution likewise changes from uniform to partitioned, and then back to uniform. This evolutionary process of strength and rheological properties of rocks during migmatization may promote strain localization at mid- crustal conditions. [ABSTRACT FROM AUTHOR]

In his comment, Gabet summarized his critiques regarding our identification of migrating knickpoints in the Sierra and our estimates of both timing and magnitude of surface uplift made using a wide variety of independent measures of fluvial geomorphology. Here, we review the evidence we used to interpret particular features as migrating knickpoints in a transient landscape and demonstrate that the evidence presented by Gabet in no way shows these are stationary features that can be attributed to heterogeneous lithology alone. The challenges we faced and assumptions we made to determine timing from these river profile forms were summarized in the original paper and again in Gabet's comment. We chose a range-wide approach using systematic topographic analysis and an ensemble of methods precisely because we recognize the modern heterogeneity and dynamic late Cenozoic geologic history. With this approach, we identified trends in timing and magnitude of surface uplift that were consistent along much of the length of the range and in both tributary and mainstem rivers. We were able to identify signatures of late Cenozoic tilting amidst the influence of heterogeneous lithology, latitudinal climate gradients, drainage area exchange, and variable depositional histories. We hope that readers recognize that rather than ignoring local complexity, the tectonic mechanism of late Cenozoic westward tilt and the ensuing transient response can explain the diversity in observed geomorphology. Particularly, geomorphic features such as the along- and between-river variability in incision as well as the distribution and form of both mainstem and tributary knickpoints and knickzones can be reconciled when such a transient response is filtered through the heterogeneous lithology and basin area exchange characteristic of the west side Sierra Nevada. Thus, while challenges preclude pinpointing timing of the most recent tectonic event within the late Cenozoic using river profile forms alone, we maintain that a significant tectonic event perturbed Sierra river profiles in the past 11 million years. In many landscapes, an estimate with such a degree of uncertainty would not move the needle on our understanding but for the Sierra, where some contend no major tectonic event has occurred since the late Cretaceous, this uncertain estimate is valuable. [ABSTRACT FROM AUTHOR]

The article presents the discussion on major tectonic event occurred since the late Cretaceous. Topics include assumptions determining the timing from the river profile forms being summarized in the original paper and again in Gabet's comment; and rock uplifted during the pulse being rapidly incised for bringing the river elevation, steepness, and erosion ratign back to the pre-tilt equilibrium condition.

The term "appinites" refers to amphibole-rich mafic rocks, as one of the most typical products of partial melting of a metasomatic lithospheric mantle. This paper presents results of integrated geochemical and isotopic analyses for six Early Cretaceous (125-119 Ma) appinitic plutons from the Liaodong Peninsula, northeastern North China Craton (NCC), to not only investigate the properties of the metasomatic lithospheric mantle induced by variable recycled crustal components but also to discuss a hydrous mantle source. The appinites originated from partial melting of sub-continental lithospheric mantle (SCLM), and can be geochemically categorized into three groups distinguished by the input of different recycled crustal components (e.g., terrigenous sediments and delaminated lower continental crust) on the basis of two distinct Hf-O isotopic arrays. Based on the occurrence of voluminous amphiboles (50-60 vol%) and minor clinopyroxene remnants, a petrogenetic model was proposed to interpret the formation of appinites. Asthenospheric upwelling caused by the subduction and roll-back of the Paleo-Pacific plate firstly resulted in partial melting of the SCLM to yield basaltic magmas. Subsequently, numerous hydration reactions between early anhydrous minerals (e.g., olivine and pyroxene) of basaltic magmas and hydrous melts derived from terrigenous sediments and delaminated lower continental crust occurred to produce the studied appinites. Ultimately, the recycled crustal materials can serve as the metasomatic agent not only to transfer the enriched isotopic signatures into the studied appinites but also to represent hydrous components to play the part of hydrous reactions. The high abundance of amphibole in the studied appinites is indicative of a hydrous lithospheric mantle beneath the eastern NCC. [ABSTRACT FROM AUTHOR]

The Sinemurian-Pliensbachian boundary event (ca. 193 Ma) is recorded as a global perturbation of the carbon cycle, as evidenced by a large negative carbon-isotope excursion recorded in many marine sedimentary successions. Whereas multiple lines of evidence testify that the Sinemurian-Pliensbachian boundary event was associated with environmental and climatic changes, sea-level oscillations, and biotic turnovers in marine settings, the record and effects of the event on continents are poorly known. In this paper, we report a high-resolution δ13Corg record and palynological data from the Lower Jurassic lacustrine succession of the Sichuan Basin that allow a prominent 8‰ negative carbon-isotope excursion to be identified at the Sinemurian-Pliensbachian transition. We therefore interpret this perturbation as the expression of the Sinemurian-Pliensbachian boundary event in the Sichuan Basin, and we propose a correlation with the marine realm. Facies evolution illustrates that the Sinemurian-Pliensbachian boundary event coincided with a phase of expansion of the lacustrine systems. Palynological analyses indicate a sharp shift from arid to humid climate conditions coincident with the carbon-isotope perturbation that supports a scenario of lake expansion driven by increased rainfall. In contrast to observations in the Sichuan Basin, where deep lake conditions persisted across the Sinemurian-Pliensbachian boundary event, a global drop in the sea level is documented at the onset of the isotope perturbation. This suggests that eustatic oscillations due to increased continental water storage in lakes and aquifers in the context of a wetter climate phase may have been associated with the early stages of the Sinemurian-Pliensbachian boundary event. [ABSTRACT FROM AUTHOR]

Field and laboratory studies of the 1959 Kīlauea Iki lava lake have provided insight into differentiation processes in mafic magma chambers. This paper explores how partially molten basaltic mushes responded to unloading as a consequence of drilling. Most holes drilled from 1967 to 1979 terminated in a melt-rich internal differentiate with a sharp crust-melt interface. These interfaces were not stable, so the boreholes were backfilled by melt-rich (<5% crystal) ooze. This process, with melt ascent rates of 1.3--4.2 m/s, occurred within minutes of intersecting the bodies, mimicking volcanic eruptions, albeit on a small scale. One borehole (KI79-1), which did not encounter such a discontinuity, was backfilled over a period of 16 days by upward flow of crystal-rich mushes rather than melt-rich ooze. The first interval of ooze recovered had undergone extensive internal differentiation. Its most conspicuous feature was production of melt-rich layers by lateral migration of interstitial melt from the wallrock into the rising crystal-rich mush. In addition, two smaller-scale processes occurred within the rising mush: segregation of melt into discrete blebs within the rising mush column and aggregation of groundmass crystals into crystal-rich clumps formed adjacent to coarser olivine crystals. The upper parts of the ooze are enriched in melt relative to deeper samples, which suggests that the melt blebs rose relative to their olivine-rich matrix. Similar melt blebs and crystal-rich clumps are observed in naturally occurring diapiric bodies within the lava lake. These processes appear to be intrinsic to the upwelling of narrow cylindrical mush bodies whether constrained within a borehole (like the oozes) or unconstrained (as were the diapirs in the lava lake). The most striking behavior observed during repeated reentry of KI79-1 was a sharp change in rheology during the second and third re-entries of the borehole. The shift in behavior observed was that the oozes rose up the borehole, with ascent rates of 1.0--1.7 m/s, which are comparable to the rates of the crystal-poor oozes from melt-rich internal differentiates. These oozes contain more melt than the original core at equivalent depths, presumably because melt moved relative to crystals down the pressure gradient created by the open borehole. Groundmass textures in these inflated mushes show erosion of crystal outlines, especially of grain-to-grain contacts between different phases, so that the tenuous crystalline network observed in the original core samples was replaced by rounded crystals in continuous melt at crystallinities of 55--65 vol%. The transition from stable coherent mush to inflatable mush occurred at 25--28 vol% melt. This behavior appears similar to certain types of reactive transport observed in other studies. [ABSTRACT FROM AUTHOR]

The Triassic tectonic setting of the Tethyan Himalaya in southern Tibet remains controversial and is key to revealing the mechanism of Neo-Tethys Ocean opening and the breakup history of Gondwana. This paper reports 227-225 Ma mafic volcanic rocks interbedded within the Tethyan Himalaya sequence in southern Tibet, which were formed in a typical passive continental margin setting. The basalts are tholeiitic with high TiO2 (3.20-3.38 wt%) and moderate MgO (4.05-5.40 wt%) contents and exhibit enrichment in light rare earth elements and weak negative Nb, Ta, Eu, and Ti anomalies. These geochemical compositions, combined with uniform whole-rock eNd(t) (+1.50 to +2.70) values, indicate that the magmas were derived by low-degree melting of a deep-seated garnet source that was heterogeneously modified by an oceanic island basalt-type of component. Given the other geological evidence, we propose that the magmatic evolution of the Tethyan Himalaya during the late Paleozoic-Mesozoic was generally a lithospheric thinning process, that is, it evolved from a fully developed continental rift system during the Late Permian to wane during the Triassic. This interpretation further supports the hypothesis that the Neo-Tethys Ocean opened in a passive pattern and that the breakup of Gondwana in the late Paleozoic was initiated by lithospheric thinning. Therefore, the subsequent magmatism was related to the passive upwelling of normal asthenospheric materials. [ABSTRACT FROM AUTHOR]

Porphyry deposits are the main source for global Cu and Mo production. The generation of hydrous silicate magmas and subsequent separation of volatile-rich magmatic fluids with hydrothermal alteration are significant processes leading to the formation of porphyry deposits. However, a specific understanding of these processes has been limited by a lack of direct mineralogical records in the evolving magmatic-hydrothermal system. In this paper, we present an integrated textural and geochemical investigation on apatite from the giant Daheishan porphyry Mo deposit in NE China, illustrating that apatite can be a potential recorder of the magmatic-hydrothermal evolution of porphyry systems. Apatite from the ore-forming porphyry displays distinctive core-rim textures, with melt inclusions in the resorption cores (Type-A1) and co-existing of melt and fluid inclusions in the euhedral rims (Type-A2), indicating a magmatic-hydrothermal origin of apatite. This is also supported by both chemical and isotopic compositions obtained by in situ analyses using laser ablation--inductively coupled plasma--mass spectrometry (LA-ICP-MS) and LA-multi collector-ICP-MS. The late Type-A2 apatite is relatively enriched in incompatible elements, such as rare earth elements (REE) and Th, but slightly depleted in fluid-mobile elements such as Na and S, compared to the early Type-A1 apatite. Relatively homogeneous (87Sr/86Sr)i ratios (0.70436--0.70504) of the Type-A1 and Type-A2 apatites indicate that they were formed in a relatively closed system without detectable contamination. Meanwhile, some apatite in the wall rock (biotite granodiorite) shows characteristics of secondary altered textures, resulting from the intensive alteration by hydrothermal fluids exsolved from the porphyry system. Apatite trapped in mineral phenocrysts of the wall rock is usually unaltered (Type-B1 apatite), with clear oscillatory growth zones in cathodoluminescence (CL) images. In contrast, the intergranular apatite is commonly altered (Type-B2 apatite), with chaotic zoning in CL images, abundant micro-fractures and secondary fluid inclusions. Compositionally, the Type-B2 apatite shows notable tetrad REE patterns, relatively lower light-REE and S contents, and elevated 147Sm/144Nd ratios compared to the Type-B1 apatite. LA-ICP-MS U-Pb dating yields a lower intercept age of 171.4 ± 2.3 Ma for Type-B2, which is consistent with the age of 171.5 ± 2.4 Ma for Type-A2, but is notably younger than the Type-B1 apatite (175.5 ± 1.3 Ma). It is suggested that the Type-B2 apatite has been significantly reset by hydrothermal fluids exsolved from the porphyry system. Therefore, we conclude that the textures and geochemistry of apatite in porphyry systems can be used as a potential proxy for recording fluid exsolution and hydrothermal alteration processes. [ABSTRACT FROM AUTHOR]

The Zagros orogen, formed by the collision of the Arabian and Eurasian continental margins, represents one of the largest and richest oil and gas provinces in the world. The Zagros fold-thrust belt records collision and convergence along the Neotethys suture zone. By coupling field observations, sandstone modal analysis, U-Pb zircon dating, and Hf isotopic data from the Upper Cretaceous to Pliocene sedimentary succession of the Neyriz region, this paper documents several major provenance changes that allow us to propose a refined scenario for the Zagros orogeny. An ophiolitic complex dated by detrital-zircon U-Pb geochronology as ca. 95 Ma provided detritus to Upper Cretaceous-Paleocene strata deposited along the northeastern margin of the Arabian lower plate (ophiolite provenance). Yet, on the southwestern margin of the Eurasian upper plate, upper Paleocene-lower Eocene strata indicate provenance from Mesozoic magmatic rocks yielding zircons dated as ca. 240 Ma and 170 Ma as well as the recycling of clastic rocks. Since the early Miocene, the sedimentary basin located on the Arabian plate received both ophiolitic detritus and magmatic-arc, recycled clastic, and axial-belt metamorphic detritus from Eurasia. U-Pb ages of detrital zircons reflect polyphase magmatism at 170 Ma, 95 Ma, and 40 Ma on the Eurasian active margin. Our results indicate that progressive accretion, uplift, and exhumation of the Zagros orogen was well under way by the beginning of the Miocene in the Neyriz region. Literature data from adjacent regions suggest that the Arabia/Eurasia collision may have occurred diachronously and later in the Kermanshah and Lurestan areas to the north. [ABSTRACT FROM AUTHOR]

In the southern Tibetan Plateau, leucogranites are dominantly distributed in the Himalayan orogenic belt with minor occurrences in the southern Lhasa subterrane. In this paper, we report the first Miocene Anglonggangri leucogranites in the northern Lhasa subterrane. This finding provides important constraints on both leucogranite petrogenesis and the tectono-magmatic evolution of the Lhasa terrane. The Anglonggangri leucogranites include biotite-muscovite granite and slightly younger garnet-muscovite granite and pegmatite. Zircon U-Pb and muscovite 40Ar-39Ar dating of these leucogranites yields Miocene ages of 11.1-10.2 Ma. The biotite-muscovite and garnet-muscovite granites are characterized by high SiO2 (72.3-74.4 wt.%) and Al2O3 contents (14.4-15.4 wt.%) and are peraluminous. The biotite-muscovite granite displays geochemical signatures with high Sr/Y (29.2-81.0) and (La/Yb)N (37.5-98.9) ratios, low Y (4.30-7.22 ppm) and Yb contents (0.26-0.47 ppm), low to moderate initial (87Sr/86Sr)i ratios (0.7085-0.7192), and moderate εNd(t) values (-10.17 to -6.94). Furthermore, they also exhibit radiogenic Pb isotope and variable zircon εHf(t) values (-9.6 to +4.4) with Proterozoic Nd (1.1-1.4 Ga) and Hf model ages (0.8-1.7 Ga). By comparison, the garnet-muscovite granite has lower CaO, MgO, TiO2, and total FeO contents and is enriched in Rb (380-466 ppm) and depleted in Sr (24.1-38.5 ppm) and Ba (30.7-58.6 ppm) and further characterized by a significant rare earth element (REE) tetrad effect and non-charge and radius-controlled (CHARAC) trace element behaviors. The garnet-muscovite granite shows a negative Eu anomaly and positive correlations among Sr and Eu, Sr and Ba, and Th and light rare earth elements (LREEs). Pegmatite comprising Nb-Ta oxides and cassiterite occurs in the garnet-muscovite granite. Geochronological and geochemical characteristics of the Anglonggangri leucogranites indicate that the magma of the biotite-muscovite granite was derived from partial melting of amphibolite lower crust contaminated with Proterozoic-Archean upper crustal materials. The garnet-muscovite granite was generated through melt extraction from the biotite-muscovite granite crystal mush. These results confirm that partial melting of the amphibolite lower crust not only occurred in the southern and central Lhasa subterranes but also in the northern Lhasa subterrane. [ABSTRACT FROM AUTHOR]

This paper provides an understanding of the sedimentary-tectonic evolution of the Cenozoic strata of the El Habt and Ouezzane Tectonic Units (Intrarif, External Rif) in Morocco. New data provide information about the depositional architecture and enable a correlation of the evolution of the External Rif in Morocco with that of the Betic Cordillera in Spain and the Tunisian Tell, which provides new insights for hydrocarbon exploration in the region regarding possible source, reservoir, and seal rocks. The reconstructed Cenozoic succession was bio-chronologically defined, and the major unconformities and stratigraphic gaps were identified. The presence of these unconformities allowed three main stratigraphic sequences to be defined by age: Danian p.p., early Ypresian--early Bartonian p.p., and the early Rupelian--early Serravallian p.p. Three secondary stratigraphic sequences in the former upper main sequence were also defined by age: early Rupelian--late Chattian p.p., Burdigalian p.p., and the Langhian--Serravallian p.p. The depositional setting evolved from deep basin during the Late Cretaceous--Paleocene to external platform-slope during the Eocene--Miocene. The Cenozoic sandstones contain metamorphic and sedimentary rock fragments derived from a recycled orogen source area. The clay mineralogy in the Cenozoic strata consists of associations of Ill+(I--S) ± Sme, Ill+(I--S) ± Sme+Kln and Ill+(I--S) ± Sme+- Kln+Chl. These associations indicate an initial unroofing in the Paleogene period, then in the Cretaceous period, and finally in the Late Jurassic period during the Eocene--Oligocene. This detritus was followed by variable amounts of a sedimentary mix of Paleogene to Late Jurassic terrains due to several phases of erosion and deposition partly related to syn-sedimentary tectonics during the Miocene. Equivalent features (similar types of sediments, tectofacies, gaps, and unroofing) were also recognized along the Betic Cordillera in Spain and Maghrebian Chain (Morocco and Tunisia) and interpreted as related to a pre-nappe tectonic activity of soft basement folding, which occurred during the Paleogene after the generalized tectonic inversion (from extension to compression) occurred in the Late Cretaceous. The Upper Cretaceous is considered to be the hydrocarbon source rock, while the fractured Eocene and the porous Oligo-Miocene suites are proposed as possible hydrocarbon reservoirs. The Cenozoic stratigraphic architecture and the nappe structure of the region could provide the necessary trap structures. [ABSTRACT FROM AUTHOR]