Search

The Middle and Lower Reaches of the Yangtze River metallogenic belt (MLYMB) is one of the most important Fe‐Cu polymetallic belts in China. However, the mechanism and deep geodynamical process for the formation of this belt are still controversial. Here, we obtain the crustal and the uppermost mantle structures using ambient noise data from a dense seismic profile. A low velocity zone is revealed beneath the Moho of MLYMB, interpreted as the source of the deep mineralization materials. In addition, a low velocity layer (LVL) and a high velocity layer (HVL) are observed in the crust of the southern segment of the profile. The LVL is interpreted as a tectonic detachment layer between the upper and the lower crust, and the HVL is interpreted as the aggregation zone for mineralizing melts or crystallized magma chambers. Based on the observed velocity features, we propose a three‐stage model for the formation of ore deposits in MLYMB. Our model suggests that an upwelling of asthenosphere triggered by the delamination of a previously thickened lithosphere leads to the partial melting of upper mantle rocks, which eventually ponders under the Moho. The magma then infiltrates through the ductile lower crust and reaches a depth of ∼7–13 km, forming a minerals‐enriched magma chamber. Minerals‐rich hot fluids originating from the magma chamber continue to move upward along the pre‐existent faults and the minerals finally precipitate in dense veinlets when reaching shallow depths, forming the ore deposits in and around the MLYMB. Plain Language Summary: The formation of large‐scale mineral deposits is closely related to the lithosphere structure. The Middle and Lower Reaches of the Yangtze River metallogenic belt (MLYMB) is an ideal place to study the mineral system, as it is one of the most important Fe‐Cu polymetallic metallogenic belts in Eastern China and contains more than 200 ore deposits. Yet the mechanism and deep geodynamical process for the formation of this belt are still controversial. In this study, we construct a high‐resolution seismic model of the crust and the uppermost mantle using ambient noise data from a dense seismic profile. Our result reveals velocity features closely related to the metallogenic process in this region. Based on the observed velocity features, we propose a three‐stage model for the formation of the ore deposits in MLYMB, which is of great importance for the development of "mineral system" approaches to the exploration of minerals worldwide. Key Points: We obtain a fine Vs structure of the crust and uppermost mantle beneath the MLYMBWe observe velocity features closely related to the metallogenic process of MLYMBWe propose a three‐stage metallogenic process for the origin of the MLYMB [ABSTRACT FROM AUTHOR]

A mosaic of terranes or blocks and associated Late Paleozoic to Mesozoic sutures are characteristics of the north Sanjiang orogenic belt (NSOB). A detailed field study and sampling across the three magmatic belts in north Sanjiang orogenic belt, which are the Jomda-Weixi magmatic belt, the Yidun magmatic belt and the Northeast Lhasa magmatic belt, yield abundant data that demonstrate multiphase magmatism took place during the late Paleozoic to early Mesozoic. 9 new zircon LA-ICP-MS U-Pb ages and 160 published geochronological data have identified five continuous episodes of magma activities in the NSOB from the Late Paleozoic to Mesozoic: the Late Permian to Early Triassic (c. 261-230 Ma); the Middle to Late Triassic (c. 229-210 Ma); the Early to Middle Jurassic (c. 206-165 Ma); the Early Cretaceous (c. 138-110 Ma) and the Late Cretaceous (c. 103-75 Ma). 105 new and 830 published geochemical data reveal that the intrusive rocks in different episodes have distinct geochemical compositions. The Late Permian to Early Triassic intrusive rocks are all distributed in the Jomda-Weixi magmatic belt, showing arc-like characteristics; the Middle to Late Triassic intrusive rocks widely distributed in both Jomda-Weixi and Yidun magmatic belts, also demonstrating volcanic-arc granite features; the Early to Middle Jurassic intrusive rocks are mostly exposed in the easternmost Yidun magmatic belt and scattered in the westernmost Yangtza Block along the Garzê-Litang suture, showing the properties of syn-collisional granite; nearly all the Early Cretaceous intrusive rocks distributed in the NE Lhasa magmatic belt along Bangong suture, exhibiting both arc-like and syn-collision-like characteristics; and the Late Cretaceous intrusive rocks mainly exposed in the westernmost Yidun magmatic belt, with A-type granite features. These suggest that the co-collision related magmatism in Indosinian period developed in the central and eastern parts of NSOB while the Yanshan period co-collision related magmatism mainly occurred in the west area. In detail, the earliest magmatism developed in late Permian to Triassic and formed the Jomda-Wei magmatic belt, then magmatic activity migrated eastwards and westwards, forming the Yidun magmatic bellt, the magmatism weakend at the end of late Triassic, until the explosure of the magmatic activity occurred in early Cretaceous in the west NSOB, forming the NE Lhasa magmatic belt. Then the magmatism migrated eastwards and made an impact on the within-plate magmatism in Yidun magmatic belt in late Cretaceous. [ABSTRACT FROM AUTHOR]

Laparoscopic hernia repair has been shown to be superior to open surgery, and it has become the preferred method for treating inguinal hernia. However, the advantages and disadvantages of laparoscopic transabdominal preperitoneal (TAPP) and totally extraperitoneal (TEP) inguinal hernia repair—the two most commonly used methods—remain controversial. Most studies of these two operation methods do not clearly present the pros and cons; only studies of curative effects or postoperative complications have provided comparisons. As techniques for laparoscopic inguinal hernia repair continue to be developed and reported in the literature, a meta-analysis might be able to reliably determine the efficacy of different methods. This analysis aims to provide a reliable basis for surgeons and patients to choose between surgical methods. To this end, we retrieved literature that compared TAPP and TEP in terms of the operation time, length of postoperative hospital stay, perioperative complications (surgery change, bleeding, visceral injury), early postoperative complications (seroma, mouth infection, urinary retention), late postoperative complications (recurrence, chronic pain), and resume normal work time. PubMed, Embase, Cochrane Library, Web of Science, and CNKI were searched for randomized controlled trials comparing TAPP and TEP prior to December 15, 2020. Retrieved papers were screened according to established criteria, and those with a quality score of ≥ 4 were included. The papers’ data were extracted, and subgroup analysis of hernia type was performed. Data related to the main comparative results (e.g., operation time, length of postoperative hospital stay, intraoperative complications, postoperative seroma) were recorded. Meta-analysis was performed using RevMan 5.3. Registration number: CRD42021233107; https://www.crd.york.ac.uk/PROSPERO). A total of 2038 papers were retrieved, and 18 were finally included. Among them, 12,746 patients received TEP, and 14,000 received TAPP. Meta-analysis results showed that TEP reduced the length of postoperative hospital stay compared to TAPP (MD: 8.87; 95% CI: 2.28–15.46; p = 0.008). TEP reduced the incidence of postoperative incision infection compared to TAPP (OR: 2.36; 95% CI: 1.19–4.66; p = 0.01). TAPP reduced the incidence of postoperative seroma compared to TEP (OR: 0.68; 95% CI: 0.50–0.91; p = 0.009). TAPP and TEP are both good surgical methods with their own advantages andisadvantages. TEP can shorten postoperative hospital stay and reduce the postoperative incision infection rate, while TAPP can reduce the incidence of postoperative seroma. In general, the choice between TAPP and TEP should be made jointly by the surgeon and the patient. [ABSTRACT FROM AUTHOR]