Hydrothermal replacement of biogenic and abiogenic aragonite by Mg-carbonates – Relation between textural control on effective element fluxes and resulting carbonate phase

Dolomitization, i.e., the secondary replacement of calcite or aragonite (CaCO3) by dolomite (CaMg[CO3]2), is one of the most volumetrically important carbonate diagenetic processes. It occurs under near surface and shallow burial conditions and can significantly modify rock properties through changes in porosity and permeability. Dolomitization fronts are directly coupled to fluid pathways, which may be related to the initial porosity/permeability of the precursor limestone, an existing fault network or secondary porosity/permeability created through the replacement reaction. In this study, the textural control on the replacement of biogenic and abiogenic aragonite by Mg-carbonates, that are typical precursor phases in the dolomitization process, was experimentally studied under hydrothermal conditions. Aragonite samples with different textural and microstructural properties exhibiting a compact (inorganic aragonite single crystal), an intermediate (bivalve shell of Arctica islandica) and open porous structure (skeleton of coral Porites sp.) were reacted with a solution of 0.9 M MgCl2 and 0.015 M SrCl2 at 200 °C. The replacement of aragonite by a Ca-bearing magnesite and a Mg-Ca carbonate of non-stoichiometric dolomitic composition takes place via a dissolution-precipitation process and leads to the formation of a porous reaction front that progressively replaces the aragonite precursor. The reaction leads to the development of porosity within the reaction front and distinctive microstructures such as gaps and cavities at the reaction interface. The newly formed reaction rim consists of chemically distinct phases separated by sharp boundaries. It was found that the number of phases and their chemical variation decreases with increasing initial porosity and reactive surface area. This observation is explained by variations in effective element fluxes that result in differential chemical gradients in the fluid within the pore space of the reaction rim. Observed reaction rates are highest for the replacement of the initially highly porous coral and lowest for the compact structure of a single aragonite crystal. Therefore, the reaction progress equally depends on effective element fluxes between the fluid at the reaction interface and the bulk solution surrounding the test material as well as the reactive surface area. This study demonstrates that the textural and microstructural properties of the parent material have a significant influence on the chemical composition of the product phase. Moreover, our data highlight the importance of effective fluid-mediated element exchange between the fluid at the reaction interface and the bulk solution controlled by the local microstructure

Negative Expressions are Shared more on Twitter for Public Figures than for Ordinary Users

Social media users tend to produce content that contains more positive than negative emotional language. However, negative emotional language is more likely to be shared. To understand why, research has thus far focused on psychological processes associated with the content of tweets. In the current study, we investigate if the content producer influences the extent to which their negative content is shared. More specifically, we focus on a group of users that are central to the diffusion of content on social media – public figures. We found that an increase in negativity was associated with a stronger increase in sharing for public figures compared to ordinary users. This effect was explained by two user characteristics, the number of followers (and strength of ties), and proportion of political tweets. The results shed light on whose negativity is most viral, allowing future research to develop interventions aimed to mitigate overexposure to negative content

Negativity Spreads More than Positivity on Twitter after both Positive and Negative Political Situations

The goal of the project was to investigate what types of emotional language spread further in response to negative and positive political situations. In Studies 1 (same situation) and 2 (separate situations), we examined the spread of emotional language in response to negative and positive situations

Social Sharing (Survey) Study

We take two routes to investigate social sharing of emotion (SSE) in the midst of the COVID-19 pandemic. The current project focuses on data collected from online surveys

Negativity Spreads More than Positivity on Twitter after both Positive and Negative Political Situations

What type of emotional language spreads further in political discourses on social media? Previous research has focused on situations that primarily elicited negative emotions, showing that negative language tended to spread further. The current project extends existing knowledge by examining the spread of emotional language in response to both predominantly positive and negative political situations. In Study 1, we examined the spread of emotional language in tweets related to the winning and losing parties in the 2016 US elections, finding that increased negativity (but not positivity) predicted content sharing in both situations. In Study 2, we compared the spread of emotional language in two separate situations: the celebration of the US Supreme Court approval of same-sex marriage (positive), and the Ferguson Unrest (negative), finding again that negativity spread further. These results shed light on the nature of political discourse and engagement

Social Sharing (Twitter) Study

We take two routes to investigate social sharing of emotion (SSE) in the midst of the COVID-19 pandemic. The current project focuses on data collected from social media (Twitter)

Study 3: Emotionality Judgments of Happiness Sequences

The goal of Study 3 was to replicate the effect of target gender on judgments of emotionality from Study 2 using expressions of happiness