A new perspective on cumulate formation and melt extraction from mushy reservoirs: the "melt flush" model

<p>Volcanism is the surface expression of extensive magmatic systems, with their intrusive counterpart representing ~80% of the total magma budget. Our knowledge of igneous processes therefore largely relies on our understanding of deep plutonic processes. In continental or oceanic environments, most of the intrusive igneous rocks bear geochemical cumulate signatures (e.g., depletion in incompatible elements, enrichment in compatible ones) that are commonly explained by minerals-melt segregation during differentiation. Nevertheless, in many cases the processes aiding melt segregation still need to be further constrained.</p><p>In oceanic environments, deformation-assisted compaction aided by melt buoyancy is the main process involved in melt extraction. However, a number of cumulative rocks are lacking any clear compaction evidence, opening the potential for the involvement of other processes. Here, relying on current descriptions of melt dynamics within oceanic magma reservoirs, i.e. the mushy nature of the reservoirs and inferred cyclic replenishment by primitive melts, we propose the involvement of a new igneous process. In the "melt flush" model, repeatedly injected fresh melts hybridize within the injected mush triggering mineral dissolution and crystallization, and concurrent partial extraction of the former interstitial melt forced out of the system by the incoming melts aided by buoyancy.</p><p>This model is consistent with the widespread occurrence of reactive porous flow (RPF) identified in oceanic igneous systems, and matches the petrographical (e.g., olivine and plagioclase dissolution) and geochemical constraints (trace element signatures) brought by natural oceanic samples. More specifically, it has been shown that RPF proceeds following melt consuming reactions that ultimately result in a progressive closure of the mush porosity. The extraction of the evolved interstitial melts replaced by more primitive ones, and the porosity closure are here proposed to account for some of the cumulative signatures observed in igneous rocks. The "melt flush" model we describe eventually adds to the other processes involved in cumulates formation from various settings like magma compaction or crystal settling.</p>

Marine Internet for Internetworking in Oceans: A Tutorial

Ever-increasing human activities in oceans require handy, reliable and cost-effective high-speed network access similar to terrestrial Internet services to be available on and under water. However, terrestrial Internet cannot be extended to oceans seamlessly due to huge differences between terrestrial and oceanic environments, while satellite services are still very expensive especially for ordinary users with communication quality susceptible to weather conditions, and cannot cover underwater networks either. Therefore, marine Internet, proposed about six years ago, is the earliest scheme that tries to systematically address the internetworking issue in oceans and still in its infancy stage. This tutorial aims to introduce the principle, architecture and applications of marine Internet, along with discussion on oceanic environments for communication, currently available and under developing communication systems in oceans, as well as challenging issues necessary for further studies to foster the development of marine Internet.

Analysis of Severe Droughts in Taiwan and its Related Atmospheric and Oceanic Environments

Drought is one of the important issues in climate studies. A drought index, Taiwan Meteorological Drought index (TMD index), was previously proposed and is applied here to identify historical severe droughts in Taiwan in order to clarify the corresponding large-scale backgrounds as a potential alert to the society in future. Through the TMD index, several historical severe drought cases in Taiwan are detected and characterized by significant seasonal variability in the annual cycle. Composites for large-scale atmospheric and oceanic environments over different periods within the dry season are conducted. From October to December, the colder sea surface temperature (SST) pattern of Pacific Meridional Mode (PMM) and the PMM-induced local anomalous anticyclones over the South China Sea are both in charge of the extremely dry conditions in Taiwan. From January to February, cold SST in the South China Sea and its adjacent oceans dominates local atmospheric conditions above these regions and creates an unfavorable environment for convection systems. From March to May, a massive anomalous anticyclonic circulation centering beside Alaska and extending its properties to East Asia and Taiwan generates a descending environment and in turn suppresses convection systems to develop. Therefore, the extremely dry conditions under this system are expected.