ABSOLUTE PALEOINTENSITY FOR PRECAMBRIAN-AGED DIKES FROM INDIA

Despite significant progress in paleomagnetic research over the last century, the origin, evolution, and long-term behavior of the geomagnetic field remains poorly understood. One significant open question is when and how the inner core nucleated. Since geomagnetic field behavior is thought to be linked to thermal evolution in the core, scientists have turned to the global paleointensity record to search for proxies for inner core nucleation. From this record, two signals have been identified as possible indicators of inner core nucleation: (1) A spike in magnetic field strength and variability between 1.5–1.0 Ga, and (2) an initially strong, but gradually decreasing field strength that results in a weak dynamo in the late Precambrian. While both these studies have vastly different results, they do have one common challenge hindering them: A paucity of paleointensity data. This is especially true for the Precambrian era for which well-preserved outcrops are scarce and weathering/alteration is almost guaranteed. Despite making up almost 90% of Earth’s history, data from this era comprises only ~8% of the global paleointensity database. This lack of data for most of Earth’s history represents a huge gap in our knowledge and greatly impedes our ability to understand the origin and evolution of our planet and its magnetic field. To aid in filling in this gap, we present new paleointensity results for several Precambrian-aged mafic dikes from India. Samples are from the Malani Igneous Suite (~752 Ma), Bastar Craton (~1.9 Ga), and Dharwar Craton (~2.37 Ga). To monitor thermal alteration and minimize the effects of non-ideal grain sizes the Thellier method using the IZZI protocol was utilized. Preliminary results corroborate previous high-quality data of similar age and support the hypothesis that the magnetic field strength was gradually decreasing through the late Precambrian.