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In the process of producing the roughly three ionizing photons per atomrequired to reionize the IGM, the same massive stars explode and eject metalsinto their surroundings. While the overly sensitive Lya transition makesGunn-Peterson absorption of background quasar light an ineffective probe ofreionization at z > 6, strong low-ionization transitions like the MgII doubletwill give rise to a detectable "metal-line forest", if metals pollute theneutral IGM. We measure the auto-correlation of the MgII forest transmissionusing a sample of ten ground based z >= 6.80 quasar spectra probing theredshift range 5.96 < z_MgII < 7.42 (z_MgII,median = 6.47). The correlationfunction exhibits strong small-scale clustering and a pronounced peak at thedoublet velocity (768 km/s) arising from strong absorbers in the CGM ofgalaxies. After these strong absorbers are identified and masked the signal isconsistent with noise. Our measurements are compared to a suite of modelsgenerated by combining a large hydrodynamical simulation with a semi-numericalreionization topology, assuming a simple uniform enrichment model. We obtain a95% credibility upper limit of [Mg/H] < -3.73 at z_MgII,median = 6.47, assuminguninformative priors on [Mg/H] and the IGM neutral fraction x_HI. Splitting thedata into low-z (5.96 < z_MgII < 6.47; z_MgII,median = 6.235) and high-z (6.47< z_MgII < 7.42; z_MgII,median = 6.72) subsamples again yields null-detectionsand 95% upper limits of [Mg/H] < -3.75 and [Mg/H] < -3.45, respectively. Thesefirst measurements set the stage for an approved JWST Cycle 2 program (GO 3526)targeting a similar number of quasars that will be an order of magnitude moresensitive, making the Mgii forest an emerging powerful tool to deliverprecision constraints on the reionization and enrichment history of theUniverse.

First measurement of the Mg II forest correlation function in the Epoch of Reionization